Taking Offense at Offense-Defense Theory
Author(s): James W. Davis, Jr., Bernard I. Finel, Stacie E. Goddard, Stephen Van Evera,
Charles L. Glaser and Chaim Kaufmann
Reviewed work(s):
Source: International Security, Vol. 23, No. 3 (Winter, 1998-1999), pp. 179-206
Published by: The MIT Press
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WDavis,
Jr.
Correspondence James
Correspondence
I. Finel
~~Bernard
Theory StacieE. Goddard
TakingOffenseat Offense-Defense
VanEvera
Stephen
CharlesL. Glaserand
ChaimKaufmann
TotheEditors(JamesW.Davis,Jr.writes):
In his article"Offense,Defense, and the Causes of War,"' Stephen Van Evera claims
that"offense-defense
theory"is "important,"has "wide explanatoryrange.... wide realworld applicability.... large prescriptiveutility.... [and] is quite satisfying"(p. 41).
Van Evera's conclusions are, however, unwarranted. First, his reformulationof
influentialargumentsmade prominentby RobertJervisstretchesthe meaning of key
concepts such that interestingavenues of empirical inquiryare closed offratherthan
opened. Second, the hypotheses-or "prime predictions"-Van Evera derives fromthe
theoryare themselvesproducts of faultydeductive logic. Furthermore,they are nontestable, presumably nonscientificin Van Evera's understandingof the term.2Van
Evera's resultsare thus of littleuse to the social scientistwho is interestedin understandingthe myriad causes of war and conditionsfacilitativeof peace.
In his classic article,"Cooperation under the SecurityDilemma," Jervisargued that
the securitydilemma is more virulentand the internationalsystem less stable when
offenseenjoys an advantage over defense. By contrast,when defense is more potent,
status quo powers find it easier to adopt compatible securitypolicies, and the pernicious effectsof internationalanarchyare greatlydiminished.3Althoughthe operationin
Politicsat Ludzvig-Maximnilians-Universitat
JamesW Davis, Jr.,is AssistantProfessor
ofInternational
He is also a NATO ResearchFellow.
Munich,Germany.
BernardI. Finel is AssociateDirectorof theNationalSecurityStudiesProgramand VisitingAssistant
at Georgetown
Affairs
University'sEdmundA.
Professor
ofNationalSecurityStudiesand International
Lord,Kristin
WalshSchoolofForeignService.He thanksDieter-Dettke,RobertHaffa,TimHoyt,Jeffrey
Lord,JamesLudes,GarySchaub,and BrentSterlingfortheircomments.
StacieE. Goddardis a doctoralcandidatein theDepartment
ofPoliticalScienceat ColumbiaUniversity.
at theMassachusetts
Relationsin thePoliticalScienceDepartment
StephenVan EverateachesInternational
He is a member
InstituteofTechnology.
oftheMIT SecurityStudiesProgram.
CharlesL. Glaseris Professor
and DeputyDean in theIrvingB. HarrisGraduateSchoolofPublicPolicy
Relationsat
Studiesat theUniversity
ofInternational
ofChicago.ChaimKaufmannis AssociateProfessor
LehighUniversity.
Security,Vol. 22,
1. Stephen Van Evera, "Offense,Defense, and the Causes of War," Initernational
No. 4 (Spring 1998),pp. 5-43. Subsequent citationsto thisarticleappear in parenthesesin the text.
2. See Stephen Van Evera, Guide to MethodsforStudentsof PoliticalScience(Ithaca, N.Y.: Cornell
UniversityPress, 1997).
3. See RobertJervis,"Cooperation under the SecurityDilemma," WorldPolitics,Vol. 30, No. 2
(January1978), pp. 167-214.
Ititeriatioinal
Secur)ity,
Vol. 23, No. 3 (Winter 1998/99), pp. 179-206
? 1998 by the Presidentand Fellows of Harvard College and the Massachusetts Instituteof Technology.
179
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International
Security23:3 | 180
alizationof theoffense-defense
balancehas been thesubjectof considerabledebate,4
theconceptas originally
employedby Jervisreferred
to themodalitiesof battlefield
conquest:military
tactics,strategy,
technology,
and the state'sgeography.
The argument'sappealderivesfromitseleganceand parsimony,
as wellas itsexplanatory
range.
Throughvariationsin a rathersimple-basicallymaterial-relationship,
we appearto
gainleverageovera wide rangeofbehavioraloutcomes.
In his reformulation
of theoffense-defense
balance,however,Van Everaadds "diplomaticfactors"
to themilitary
and geographic
factors
identified
byJervis.
In doingso,
Van Everasubsumesundertheoffense-defense
balancemuchofwhatwe thoughtthe
balance helped explain.When "collectivesecuritysystems,defensivealliances,and
balancingbehaviorby neutralstates"(pp. 21-22) are all constitutive
of theoffensedefensebalance,we are no longerin a positionto ask whichmilitary
and geographic
factors
promotebalancing,
bandwagoning,
orefforts
at collective
howtheydo
security;
so; or how thebalancebetweenoffenseand defenseinteracts
withthesediplomatic
variablesto producesuch outcomesas war,peace, or overallsystemstability.
Van
Evera'sredefinition
of the offense-defense
balance is a step backward,a regressive
reformulation
ofa heretofore
usefulconcept.
A secondproblememergesbecauseVan Everafailsto keep thematerialor "objective"offense-defense
balanceanalytically
distinct
fromthebalanceas itis perceivedby
theactors.Thatactorsmightnotapprehendthetrueor objectivestateof theoffensedefensebalancewas alreadyrecognizedby Jervis.5
The manifest
difficulties
thatdisto use the
crepanciesbetweentheobjectiveand perceptualbalanceraiseforattempts
conceptin actualempiricalinvestigations
were,however,onlylaterappreciated.6
Theindividualtheorist
maycomedownon oneortheothersideoftheobjective/perceptualdivide,or she maychooseto testwhichof thetwo variantsaccountsforoutruledout,however,
comesin a givencase.Logically
is thecombination
ofbothin a given
Yet thisis preciselywhatVan Evera attemptsto do: "Warwill be more
hypothesis.
commonin periodswhenconquestis easyor is believedeasy,less commonwhenconor is believeddifficult"
thehypothesis
is imprequestis difficult
(p. 22).As formulated,
and as a resultcannotbe testedin anymeaningful
fashion.
cise,internally
incoherent,
4. See, forexample, JackS. Levy,"The Offense/DefenseBalance of MilitaryTechnology:A Theoreticaland HistoricalAnalysis,"International
StudiesQuarterly,
Vol. 28, No. 2 (June1984), pp. 219238; ScottD. Sagan, "1914 Revisited:Allies, Offense,and Instability,"
International
Security,
Vol. 11,
No. 2 (Fall 1986), pp. 151-175,esp. p. 161; Sean M. Lynn-Jones,
"Offense-DefenseTheoryand Its
Critics," Secuirity
Studies,Vol. 4, No. 4 (Summer 1995), pp. 660-691; and Charles L. Glaser and
Chaim Kaufmann,"What Is the Offense-DefenseBalance and Can We Measure It?" International
Secutrity,
Vol. 22, No. 4 (Spring 1998), pp. 44-82.
5. Jervis,"Cooperation under the SecurityDilemma," pp. 190-194.
6. See, forexample, the ratherad hoc justificationthatThomas Christensenand JackSnyderoffer
foradopting the perceptualbalance in theiramended Waltzian model of the balance of power in
Christensenand Snyder,"Chain Gangs and Passed Bucks: PredictingAlliance Patternsin Multipolarity,"International
Organization,
Vol. 44, No. 2 (Spring 1990),p. 145. See also Snyder,"Perceptions
of the SecurityDilemma in 1914," in RobertJervis,Richard Ned Lebow, and JaniceStein, eds.,
Psychology
an1dDetewrence(Baltimore,Md.: JohnsHopkins UniversityPress, 1985),pp. 153-179; and
RichardNed Lebow, BetweenPeaceand War(Baltimore,Md.: JohnsHopkins UniversityPress,1981),
chap. 7.
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| 181
Correspondence
logicallywe
Iftwodimensions
areat work-one objectiveand one perceptual-then
Thatis, conquestcan be (1) easy and believedto be
have fourpossiblecombinations.
but believedto be easy; or (4)
(3) difficult
easy; (2) easy but believedto be difficult;
and believedto be difficult.
difficult
of the two variantsof the
At least two cases contemplated
by the permutation
balancecannotbe includedin thesamehypothesis,
becausetheystand
offense-defense
thatsimultanein logicaloppositionto each other.Thuswe cannothave a hypothesis
believeoffense
becausepeoplemistakenly
ouslypredictswar to be relatively
frequent
we cannot
to be dominantand rarebecausethedefenseis in factdominant.Similarly,
have a situationwherewar is predictedto be rarebecausethedefenseis believedto
butwherein factoffense
is dominantand thehypothesis
be dominant,
simultaneously
And if perceptions
always trackthe "objective"
predictswars to be morefrequent.
woulddictatewe leaveperceptions
outofour
offense-defense
balance,thenparsimony
that
fromtheprimeprediction
theoryand thusrejectthetwoclassesofcases emerging
is dominantand believedto be dominant,
and
are notruledoutby logic(i.e.,offense
defenseis dominantand believedto be dominant).Moreover,such cases would be
ifwe are interested
in finding
out how perceptions
matter.
uninformative
Third,Van Everaoverstatestheextentto whichhis theorystandsup to empirical
tests.He arguesthat"thestrength
of a passed testdependson theuniquenessof the
predictions
tested.Do othertheoriespredicttheoutcomeobserved,or is theprediction
here seem quite unique. Thereis no
unique to the testedtheory?The predictions
in European
obviouscompeting
explanation
fortheperiodicupsurgesand downsurges
theoryhas the fieldto
expansionismand warfareoutlinedabove. Offense-defense
itself"(p. 35).
explanation,
evenifmerely
Everyhypothesis
is,however,
testedagainsta competing
a hypothetical
Butgiventhateveryoutcomeis in somewayconsistent
counterfactual.7
withVanEvera'shypothesis,
a hypothetical
counterfactual.8
one cannotevenformulate
in ascribingsomeplausibility
to
Moreover,
it is generally
acceptedthatone is justified
a theory's
theory.9
explanatory
claimsonlyafterithas beentestedagainsta competing
to thedegreeto whichthey
Theoriesand hypotheses
are "fortified"
or "strengthened"
Van Everais thus
pass teststhatare suggestedin lightof competingexplanations.10
7. See James D. Fearon, "Counterfactualsand Hypothesis Testing in Political Science," World
Politics,Vol. 43, No. 2 (January1991), pp. 169-195.
8. This has the effectof closing offa traditionalescape route for structuraltheorists(i.e., the
argumentthattheirtheoryexplains only tendenciesand not particularoutcomes,because tendencies are demonstrableonly to the extentto which we can clearlyidentifyoutliers).
9. For an argument with roots in Popper, see Paul Feyerabend,"Problems of Empiricism,"in
Robert Colodny, ed., Beyondthe Edge of Certainty(Englewood Cliffs,N.J.: Prentice-Hall,1965);
Feyerabend,"Reply to Criticism,"in RobertS. Cohen, ed., BostonStudiesin thePhilosophy
ofScience,
Vol. 2 (New York:Humanities Press, 1965), pp. 223-261, esp. p. 227; and Imre Lakatos, "Methodology of ScientificResearch Programmes,"in Lakatos and Alan Musgrave, eds., Criticismand the
GrowthofKnowledge(Cambridge: Cambridge UniversityPress, 1970), p. 190. Even Thomas Kuhn
stressed his acceptance of this criterion,although under certain limited conditions. See Kuhn,
"Logic of Discovery or Psychologyof Research?" in ibid., pp. 1-23.
10. For discussions of hard or crucial testsin the social sciences,see Harry Eckstein,"Case Study
and Theoryin PoliticalScience," in Fred Greensteinand Nelson Polsby,eds., HandbookofPolitical
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International
Security23:3 | 182
understanding
of hardtestswhenhe writes:"Alternative
promoting
an unorthodox
explanations
fortheriseand fallofAmericanglobalactivismarehardtocomeup with,
so this
theory'sexplanationwithoutstrongcompetitors,
leavingthe offense-defense
elementofthetestposed by theU.S. case is fairlystrong"(p. 40).
in war propensity
forvariations
abound.
Of course,seriousalternative
explanations
For example,based on a studyof the Europeanstatessystemfrom1640 to 1990,
ofthecoherence
oftheprincipal
is a function
AndreasOsianderconcludedthatstability
And alsystemis founded.1"
(normative)assumptionsupon whichan international
power,and geographic
thoughhe does not dismissthe effectsof "size, structure,
arguesthatthechiefdifference
positionofthevariousEuropeanstates,"Paul Schroeder
and themorepeacefulConcert
betweentherelatively
war-prone
lateeighteenth
century
of Europea generation
laterwas the lack of consensusamongthe greatpowerson
legitimate
principles
ofconductand an equitablebalanceofpowerpriorto theNapoleonicWars.12
Van Evera'sdiscoverythathe has thefieldto
Giventheexistenceof competitors,
moreakinto solitaire
himselfsuggeststhathe is eitherlost,or is playingsomething
thanto science.
W Davis,Jr.
-James
Munich,Germany
I. Finelwrites):
To theEditors(Bernard
ofoffense-defense
theory
considerations
Severalrecentarticleshaveprovidedtextured
These workshave
balanceon statebehavior.1
and theimpactof the offense-defense
refinements
to theargument.
theconceptuallogicand added much-needed
tightened
theoryremain,however.First,offenseFour major problemswith offense-defense
in warfare.Second,it makesill-considered
defensetheoryignoresinteraction
effects
in war.
aboutthelinksbetweencontrolofterritory,
conquest,and victory
assumptions
Finally,the
noroperationalized.
Third,thetheoryis stillneitherwell conceptualized
approachlacksparsimony.
Science,Vol. 7, StrategiesofInqluiry(Reading, Mass.: Addison-Wesley,1975), esp. pp. 118-120; and
Arend Lijphart,"Comparative Politics and the Comparative Method," AmericanPoliticalScience
Reviezv,
Vol. 65, No. 3 (September 1971), esp. pp. 692-693.
11. Andreas Osiander, The States Systemof Euirope,1640-1990: Peacemakingand the Conditionsof
International
Stability(Oxford:Clarendon Press, 1994).
12. Paul W. Schroeder,The Transforination
ofEluropean
Politics,1763-1848(Oxford:Clarendon Press,
1994), quotation at p. 10. For a similar argument,see Henry A. Kissinger,A WorldRestored:
Metternich,
and theProblemns
Castlereagh,
ofPeace,1812-1822 (New York:Grossetand Dunlap, 1964).
1. Most notably,Stephen Van Evera, "Offense,Defense, and the Causes of War," International
Vol. 22, No. 4 (Spring 1998), pp. 5-43; Charles L. Glaser and Chaim Kaufmann,"What Is
Seclurity,
the Offense-DefenseBalance and Can We Measure It?" International
Secuirity,
Vol. 22, No. 4 (Spring
1998), pp. 44-82; and Sean M. Lynn-Jones,"Offense-DefenseTheory and Its Critics," Seclurity
Vol. 4, No. 4 (Summer 1995), pp. 660-691.
Stludies,
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| 183
Correspondence
Effects
TheImportance
ofInteraction
variable.2
Ratheritcan be influenced
by
balanceis nota structural
Theoffense-defense
Thisfactcreates
strategies.
and employment
immediatedecisionsaboutdeployments
difficulties
forCharlesGlaserand ChaimKaufmannas theytryto use thetoolsofnet
balance.3
quantifythe offense-defense
assessmentto operationalizeand potentially
AreGlaserand Kaufmann
Theirarticleis vague aboutthemeaningofnetassessment.
and Andrew
to netassessmentas used by EliotCohen,AndrewKrepinevich,
referring
as well as military
Marshall-thatis, broad-based,subjectiveanalysesof nonmilitary
Or are theyreferring
to campaignanalysis-thatis, theuse ofmathematical
factors?4
Camengagements?5
modelsto predictthe resultsof highlyspecifiedforce-on-force
fittheirgoal,buttheproblemis thatcampaignanalysis
paignanalysiswouldcertainly
usuallyrelieson ForwardEdge of theBattleArea (FEBA) models.FEBA modelsare
but not necessarily
of dynamic,
warfare,
usefulin explainingthe resultsof attrition
warfare.
maneuver-based
warfare,it is possibleto use
To predicttheoutcomeof dynamic,maneuver-based
and theyare
results,
complexwar games.Thesewar gamesrarelycreatereproducible
in theinitialrules.However,war gamesusually
sensitiveto modification
extremely
effects
of
the interaction
and moreimportant,
thatdifferent
strategies,
demonstrate
makea big difference.
Ifwe takethewar-gameapproachseriously,
different
strategies,
variable,but
thenwe mustconcludethattheoffense-defense
balanceis nota structural
an outgrowth
ofstrategic
interaction.6
doctrine,
and
strategies,
dependson employment
ofbattlesystems
The effectiveness
and tactics.Changesat thesethreedistinctlevelsof analysisare potentially
training
capableof alteringthecourseof a battle.7For example,theSchlieffen
independently
level.It
Plan determined
theinitialcourseofWorldWarI in theWestat thestrategic
points,
determined
how theGermanswould mobilizetheirforces,theirconcentration
and
and theiroperationalgoals.In theend,theSchlieffen
Plan'sflaws-overextension
totheconceptual
an uncoveredrightflank-doomedtheGermanattack.Doctrinerefers
2. Cf. Glaser and Kaufmann,"What Is the Offense-DefenseBalance?" p. 55.
3. Ibid., p. 76.
4. Andrew W. Marshall,ProblemsofEstimnatingMilitaryPozver(Santa Monica, Calif.: RAND, 1996);
Eliot A. Cohen, "Net Assessment:An AmericanApproach," unpublished paper presentedas JCSS
(JaffeeCenter forStrategicStudies) Memo No. 29 (April 1990); and Cohen, "Toward BetterNet
Assessment,"International
Security,
Vol. 13, No. 1 (Summer 1988), pp. 50-89.
5. RobertP. Haffa,Jr.,RationialMethods,Prldent Choices:PlanningU.S. Forces(Washington,D.C.:
National Defense UniversityPress, 1988); Joshua M. Epstein, The Calculus of ConventionalWar:
Analysis withoutLanchiester
Equationis(Washington,D.C.: Brookings Institution,1985);
Dyniamnic
ForceReductions:A Dynanic Assessmenit
Epstein,Coniventional
(Washington,D.C.: BrookingsInstitution,1990); and Alain C. Enthovenand WayneK. Smith,How MaclhIs Enouggh?
ShapingtheDefense
Progran,1961-1969 (New York: Harper and Row, 1971).
6. As an empiricalexample, the German attackon France in 1940 did not succeed quicklybecause
of offensivedominance.Ratherthe German advance throughthe Ardennesto the EnglishChannel
coast was particularlyeffectivebecause the Franco-Britishforceswere pivoting into Belgium at
the time.Martinvan Creveld et al., Air Powerand ManeuverWarfare
(Maxwell Air Force Base, Ala.:
Air UniversityPress, 1994), p. 41.
7. JohnJ.Mearsheimer,Conventionial
Deterrence(Ithaca, N.Y.: Cornell UniversityPress, 1983).
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23:3 | 184
Security
International
doctrinewas a complexmeldingof
The blitzkrieg
basis fora tacticalbattlesystem.
of theblitzadvances.The development
armor,airpower,and disruptivepenetrating
of the preof theemergingtechnologies
kriegconceptallowed forthe exploitation
effectiveness.
increasein military
WorldWarII period,thusleadingto a discontinuous
commanders
Trainingand tacticsrefersto how forcesactuallyfight.Are subordinate
orwaitfororders?Do unitsengageorbypassenemystrong
trainedtotaketheinitiative
barrages,
ordo theyseektomaintainthe
artillery
points?Do forceslaunchpreparatory
the
tactics,forexample,jumpstarted
elementof surprise?The adoptionof infiltration
Significantly,
all threelevelscan
ofMarch1918on thewesternfront.
Germanoffensive
forcesin being.Not onlyare therealmostalways
of thecurrent
varyindependently
at anyleveloftechnology,
and usage doctrines
severalplausibletacticalbattlesystems
interaction.
and doctrines
generatea systemofstrategic
butthesebattlesystems
Warfare
is fundamentally
a "rock,paper,scissors"game.Choicesare onlydominant
dominatedheavyinlightmissileinfantry
vis-a-visotherstates'choices.Historically,
to heavy
armedwithpikesor spearswas invulnerable
fantry,
while heavyinfantry
whichlackedthe
cavalry.But heavyshockcavalryalwaysdominatedlightinfantry,
abilityto resistcharges.If theopponentwas fieldinga heavycavalryforce,thebest
force.Butiftheopponentwas armed
was a heavyinfantry
defensivecountermeasure
The optimalchoice
withheavyinfantry,
was lightinfantry.8
thebestcountermeasure
dependson theopponent'sdecisions.
ofa specific
Combinedarmswarfare
is theresponseto thisfact,buttheeffectiveness
balanceof forcesin a combinedarmssystemis also subjectto strategicinteraction.
theeffectiveness
ofanyweaponssystemand anycombinedarmssystem
Furthermore,
dependson how theforcesare beingused. Are theforcesbeingused as raidersor as
The dynamics
Are theybeingused offensively
or defensively?9
holdersof territory?
plan geared
butconsiderthissimpleexample:a strategic
hereare harderto illustrate,
towarddefeatingan enemyarmywill workonlyiftheopponentis willingto stand
Iftheopponentchoosesto use a Fabianstrategy
ofavoidingconflict
instead,
and fight.
theplan maycometo naught.
Conquest,and Victory:UnpackingtheAssumptions
Territory,
This lastpointaboutthesuccessof war plansraisesa secondproblemwithboththe
Van Evera and the Glaser and Kaufmannarticles.Botharticlesassume thatwhen
touse force.10
Thelogicis flawed.
is easier,thereis a greater
propensity
seizingterritory
is the
thattheexpectedrapidityofvictory
has arguedconvincingly
JohnMearsheimer
is
in decisionsto use force.11
The problemis thatseizingterritory
crucialdeterminant
8. ArcherJones,The Art of War in the WesternWorld(New York: Oxford UniversityPress, 1987),
p. 494.
9. For an extended examinationof warfarein the West that focuses on differentstrategiesand
interactioneffects,see ibid., passim.
10. Glaser and Kaufmann,"What Is the Offense-DefenseBalance?" p. 47.
p. 64.
11. Mearsheimer,Conventional
Deterrenice,
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| 185
Correspondence
is neither
withvictory.
notsynonymous
Indeed,seizingand holdingterritory
necessary
to win a war.
norsufficient
Warsare won undertwo conditions.
First,it is possibleto win a war by effectively
theabilityoftheotherside to resist.WiththeexceptionofWorldWarII in
eradicating
Europe,however,no war in modernhistoryhas ended as a resultof the absolute
The secondway to wina waris by
and occupationofa country's
destruction
territory.
eitherinflicting
highercoststhantheotherside can acceptor threatening
crediblyto
do so. In manycases,thiscosttoleranceis notan objectivemeasure,butrathera setof
socialconstructions.12
It is possibleto inflict
thesecostswithoutoccupyingterritory.
Indeed,formuchof
recordedhistory,
the normwas forthe losingside to concedethe issue of the war
defeatin a majorbattle,evenwhenthisdid not,in anysignificant
and lasting
following
way,underminethelosingside's abilityto wage war.In addition,historically,
many
warshavebeenwon usingraidingstrategies
in whichcontrolofterritory
is notsought.
In ancientGreece,raidingwas thedominantstrategy.
Alexander'sdefeatofPersiawas
not theresultof his abilityto controlterritory.
Even in theAmericanCivil War,the
devastating
impactof WilliamTecumsehSherman'smarchto thesea had nothingto
do withhis abilityto controlterritory.13
To theextentthatitis notnecessaryto controlterritory
to wina war,offense-defense
theorybeginsto breakdown.Ifdefeating
enemyarmiesand inflicting
costsare major
a fundamentally
priorities,
defense-dominant
world,givena low enoughforce-to-space
In 1866PrussiadefeatedAustriaby winninga
ratio,can lead to veryrapidvictories.
relatively
indecisivevictoryat K6niggratz-theAustrianswere able to withdrawin
good orderand linkup withreinforcements
fromItaly14-therebycausinga political
crisisin Vienna.In 1870thePrussianswon a setofdecisivevictories
againstFranceby
usingturningmaneuversto wage an offensive
strategy
usingthe tacticaldefensive.
These two veryrapid and low-costvictoriesoccurredin an era of extremedefense
dominancein termsof tacticalmilitary
factors.
The explanationis thatsuccessin war
and theabilityto seize and hold territory
are notcoterminous.
TheImnplication
TheProblemofPost Hoc Justifications
ofComplexity:
balanceis worthexamining
Althoughone mightarguethattheoffense-defense
on its
own terms,offense-defense
theoryis ofteninvokedas a conciseway to expandthe
15
richness
ofsystemic
modelsofinternational
and evenforeign
relations,
conflict,
policy
Thus muchof the value of offense-defense
theoryderivesfromits contribution
to
and parsimonious
and predictive
buildingrich,powerful,
theories.
explanatory
12. JohnKeegan, A Historyof Warfare
(New York:AlfredA. Knopf,1993), pp. 23-60.
13. Jones,The Artof Warin the WesternWorld,p. 417.
14. Ibid., p. 397.
15. See, for instance,Thomas J. Christensenand JackSnyder,"Chain Gangs and Passed Bucks:
PredictingAlliance Patternsin Multipolarity,"InternationalOrganization,Vol. 44, No. 2 (Spring
1990), pp. 137-168.
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International
Security23:3 | 186
In his article,Van Everacitesmilitary
factors,
geography,
socialand politicalorder,
and diplomaticfactorsas causes of offenseand defensedominance.16
Althoughhe
to aggregatetheseintoa singleoffense-defense
attempts
measure,thesevariablesare
vague,toodisparateto aggregate,
and extremely
dependenton subjective
assessments.
Theyproducea wide varietyof conflicting
theoretical
predictions,
mostof whichcan
be resolvedonlyby empiricalanalysis.
It is difficult
to avoid analyticalbias in thisprocess.Forinstance,
Van Everaargues
that"popularity
ofregimesprobablyaided offense
beforeroughly1800and has aided
defensesincethen.The reversalstemsfromtheappearanceof cheap,mass-produced
weaponsusefulforguerrillawarfare-assaultriflesand machineguns,lightmortars,
and mines.The weaponsofearlytimes(swordand shield,pikeand harquebus,heavy
17 Therewere,
slow-firing
muskets,etc.)werepoorlyadaptedforguerrillaresistance."
however,many guerrillacampaignsbefore1800.18Longbowsand crossbowswere
In thiscase, it is difficult
adequateguerrillaweapons.19
to see how thecodingcan be
done a priori.IfVanEveraused thefactthatguerrillacampaignsweremorecommon
and successful
after1800as a basisforthejudgment,
thenhe mayhaveconflated
causes
and outcomes.In any case, theargumentis underspecified
because thebasic coding
criteria
are notexplicit.
This lack of explicitcriteriacreatesambiguitiesin Van Evera'sarticle.Van Evera
mass infantry
enhancetheoffense,
but he also
factorsfavoring
suggeststhatmilitary
stressesthelimitations
on offensive
actionimposedby thelogisticaldemandsoflarge
becausetheyare expensiveand hencelimitedin number,
forces.20
are
Cavalryforces,
but tacticallyanalogous
arguedto favorthe defensedespitetheirgreatermobility,
thancavalry)aresaid
armoredforces(althoughwithevenlargerlogistical
requirements
to favorthe offense.Mass infantry
in the NapoleonicEra favorsthe offense.Mass
infantry
duringWorldWarI favorsthedefense.According
toVanEvera,thisdistinction
is theresultof "lethalsmallarms,barbedwire,and trenches."21
However,Borodino
and Waterloo-Napoleon'stwo majorsetbacksand the two mostprominent
battles
thedefensivepowerof
wherehe foughta steadyfoein a frontal
assault-demonstrate
mass infantry
evenin theearly1800s.Anotherexampleofthiscodingproblemcan be
articles.
WhereasGlaser
foundbycomparing
theVanEveraand Glaserand Kaufmann
and Kaufmannarguethat"themostwidelyagreedproposition
is thatimprovements
in mobility
favoroffense,"22
Van Everaarguesthatchariots,
and railroads-all
cavalry,
16. Van Evera, "Offense,Defense, and the Causes of War,"pp. 16-22.
17. Ibid., p. 20.
18. Keegan, A Historyof Warfare,
pp. 5-11; Jones,The Art of Warin the Western]
World,pp. 55-65;
and Donald Kagan, "AthenianStrategyin thePeloponnesian War,"in WilliamsonMurray,MacGregor Knox, and Alvin Bernstein,eds., The Makiingof Strategy:Rulers,States,anidWar (Cambridge:
Cambridge UniversityPress, 1994), p. 44.
19. BernardBrodie and Fawn Brodie,FromCrossbozv
to H-Bomb(Bloomington:Indiana University
Press, 1973), pp. 35-39. Crossbows are extremelyeasy to use, and longbows were widely available
huntingweapons in areas where huntingsupplemented local food production.
20. Van Evera, "Offense,Defense, and the Causes of War,"pp. 16, 17.
21. Ibid., p. 17.
22. Glaser and Kaufmann,"What Is the Offense-DefenseBalance?" p. 62.
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Correspondence
| 187
The othervariablescitedby Van
systemsthatenhancemobility-helpthedefense.23
Everaand Glaserand Kaufmann-theimpactofgeography,
socialand politicalorder,
and diplomaticfactors-areevenless susceptibleto clearcoding.
A largerproblemis Van Evera'sbeliefthatthesevariablescan be aggregated.
This
is troubling
froma methodological
perspective.
Van Everadoes notpresentany conceptualexplanationforhow he actuallymeasurestheoffense-defense
balancein each
area.Instead,he presentsa laundrylistof thingsto look for.Nor does he explainthe
relativeweightshe uses in aggregating
hisoffense-defense
variables.Thisleads to such
confusing
passagesas, "Sometimestechnology
overrodedoctrine,
as in 1914-18and in
1945-91(whenthesuperpowers'
militaries
embracedoffensive
doctrines
butcouldnot
findoffensive
countersto thenuclearrevolution).
Sometimesdoctrineshapedtechnoldoctrinefashionedarmortechnology
intoan offenogy,as in 1939-45,whenblitzkrieg
siveinstrument."24
Without
a setofcontingent
abouttheconditions
that
generalizations
definethe"sometimes,"
thetheoryassumeswhatit oughtto demonstrate.
whatGiovanniSartoricalled"conceptmisformaOffense-defense
theoryrepresents
tion."25
Sartoriargued,"Thelowerthediscriminating
powerofa conceptualcontainer,
themorethefactsare misgathered,
i.e.,thegreaterthemisinformation."26
Bydefining
thebalanceas beinga function
and variables,
ofa vast,unrelated
grabbag ofconditions
Van Evera and Glaserand Kaufmannhave createda situationwherethe empirical
referents
become merelya menu of itemsto choose fromto justifya preexisting
ofwhattheoffense-defense
balanceis at a givenpointintime.Thisproblem
assessment
is exacerbated
becausemostobservers
begintheirresearchwithsignificant
knowledge
and preconceptions
aboutwhattheoffense-defense
balancewas duringtheparticular
withthecases almostcertainly
leads to bias in interpreperiodtheystudy.Familiarity
tations.Glaserand Kaufmanncompoundthisproblemwiththeirmethodological
apand do some net
proach.Theyassumethatifyou throwtherightvariablestogether
balance will emerge.This sortof naked empiricism
the offense-defense
assessment,
does notadvancethecause of theorybuilding.
A ParsimoniousAddition?
It mightbe possiblefora historically
knowledgeableand methodologically
sophisticated scholar to develop a comprehensive
model of the causes of the offensebe
defensebalance.The extraordinarily
complexresulting
modelwouldnot,however,
parsimonious.
A fullyspecifiedmodelofthesourcesofoffense
and defensedominancewouldtake
of different
intoaccountthe interaction
possiblebattlesystems
and different
usage
options.Thisprocesswould createa broadtypological
theory.
Thenby examining
the
cost of the competingsystem,we mightbe able to derivea crude offense-defense
23. Van Evera, "Offense,Defense, and the Causes of War," pp. 16-17.
24. Ibid., p. 18.
25. Giovanni Sartori,"Concept Misformationin Comparative Politics,"AmericanPoliticalScience
Review,Vol. 64, No. 4 (December 1970), pp. 1033-1053.
26. Ibid., p. 1039.
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International
Security23:3 | 188
balancefora giventypological
space. Thisresultwould thenneed to be validatedby
somesortofempiricalanalysisacrosscases.Giventhattheprocessofoperationalizing
thebalanceis unwieldy,
andbudgetary
and campaign
involving
complicated
theorizing
theoffense-defense
balanceadds sufficient
analysis,itis reasonabletoquestionwhether
theverysignificant
richnessand explanatory
powerto justify
loss in parsimony.
Conclusion
Offense-defense
flawedand conceptuallymuddled.Altheoryis methodolog.ically
it
thoughVan Everaand Glaserand Kaufmannpush offense-defense
theoryforward,
is timeto ask whetheroffense-defense
theoryin factmoves the fieldforward,or
itrepresents
whether
insteadthesecurity
studies'versionoftheemperor's
newclothes.
Defendersof offense-defense
theorywill likelymakeseveralresponses.First,they
will correctly
argue thatI fail to addressthe perceptualvariantof offense-defense
balanceis notan objectiveor structural
conditheory.
However,iftheoffense-defense
thenit oughtto be intetion,but insteadresidespurelyin therealmof perceptions,
framework
ratherthanheldapartas a specialsortof
gratedintoa cognitive-processes
(mis)perception.
Second,defenders
ofoffense-defense
theorywillclaimthatI overstate
thedifficulty
ofoperationalizing
thebalanceor thatI overemphasize
thecomplexinteraction
effects
and usage decisions.If thatis thecase, however,
of tacticalbattlesystems,
doctrines,
thenI would simplyask themto demonstrate
the operationalization
processin a
manner.Untilthattime,I willremaina skeptic.
systematic,
reproducible
Third,offense-defense
theorists
willarguethatI overstatetheproblemwithrelying
on seizingterritory
as a measureofoffensive
success.Theymayclaimthatsubstituting
is a simplechangethatdoes notharm
"victory"for"conquest"or "seizingterritory"
I wouldargue,however,
thetheoretical
thatonceonebreaksthelinkbetween
construct.
and victory,
ease ofseizingterritory
one is leftwiththefactthatnoneoftheempirical
indicators
all
fashion.Thisis nota semanticdistinction.
operatesin a consistent
Rather,
the"causes" of theoffense-defense
balanceare derivedfromtheease ofseizingterriis questionable.
tory.Once thatlinkis broken,theentirelogicoftheargument
will claimthat
Finally,and linkedto thepreviouspoint,offense-defense
theorists
evenifmyarguments
aboutinteraction
and mobilewarfarearevalid,thetheoryis still
usefulbecause it explainsthe conditionsunderwhichbreakthroughs
occur.These
offense-defense
theorists
forany kind
breakthroughs,
mightargue,are a prerequisite
of military
and theyrequirethe sortof frontal,
attrition
assaultstherelative
victory,
costsofwhichoffense-defense
theoryclaimsto measure.The problemwiththisargumentis threefold.
First,althoughthecostsofbreakthrough
maybe relatively
higheror
on a narrowfront
forthe
lower,breakingthrough
maynotraisethecostssignificantly
campaignas a whole.Second,thissortof breakthrough
impliesa situationof high
ratiosand a continuousfront.
thisis nota commoncondiforce-to-space
Empirically,
tion.Third,breakthroughs
do not necessarilyrequireattrition
and frontalassaults.
Frontscan be brokenby infiltration
tacticsand can usually be outflankedby a
foe.
sufficiently
imaginative
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| 189
Correspondence
So whatcan be done?Can offense-defense
theory
be saved?Theshortansweris,no.
Offense-defense
theoryhas too manycriticaland fatalflaws.Ifwe cannot"uninvent"
thenwe mustbe verycautiousabouthow we use it.Thereis
offense-defense
theory,
an unfortunate
tendencyin thefieldto believethatoffense-defense
theoryis a cheap
and easy way to add predictive
powerto an explanatory
model.In reality,
theissues
raisedby offense-defense
theoryare extremely
complexand difficult
to parse effectively.The theorycreatesmoreconceptualholesthanit fills,and shouldcomewitha
strongwarninglabel attached.
-BernardI. Finel
D.C.
Washington,
To the Editors (Stacie E. Goddard writes):
recentcontributions
StephenVan Evera'sand CharlesGlaserand ChaimKaufmann's
arewelcomeexpansionsofoffense-defense
toInternational
Security
theory.1
Botharticles
are intuitively
and
recognizethatalthoughhypothesespresentedin this literature
hassuffered
froma lackofmethodological
empirically
plausible,offense-defense
theory
areoftentautological;
thevariablesofoffense
and defensedominance
rigor:definitions
withotherfactorssignificant
are continuously
conflated
to international
relationstheseem to be nothingmorethan"folktheorems"
derived
ory;and at timeshypotheses
whilebotharticlesattemptto
fromthepopularcase of WorldWar1.2 Unfortunately,
addressand overcomethesecritiques,
resolvesthemethodological
neither
satisfactorily
mentioned
theoffenseabove. Mostnotably,
theseauthorsdo notdistinguish
problems
defensebalancefromfactorssuch as thebalanceof powerand military
skill.This in
turnleaves them vulnerableto tautologicalpropositions,
overdetermination,
and
and testing.
difficulties
withempiricalmeasurement
1. See Stephen Van Evera, "Offense,Defense, and the Causes of War,"International
Security,Vol.
22, No. 4 (Spring 1998), pp. 5-43; and Charles L. Glaser and Chaim Kaufmann,"What Is the
Offense-DefenseBalance and Can We Measure It?" International
Security,Vol. 22, No. 4 (Spring
1998), pp. 44-82. Offense-defensetheoryholds that under conditionsof offensedominance, war
is more likely between states. The seminal work on offense-defensetheory is Robert Jervis,
"Cooperation under the SecurityDilemma," WorldPolitics,Vol. 30, No. 2 (January1978), pp. 167214. Other works include Stephen Van Evera, Causes of War,Vol. 1: The StructureofPowerand the
Rootsof War (Ithaca, N.Y.: Cornell UniversityPress, forthcoming);
JackSnyder,The Ideologyofthe
MilitaryDecisionMakingand theDisastersof1914 (Ithaca, N.Y.: Cornell UniversityPress,
Offensive:
1984); Stephen M. Walt,Revolutionand War(Ithaca, N.Y.: Cornell UniversityPress, 1996); Quincy
Wright,A Study of War,2d rev. ed. (Chicago: Universityof Chicago Press, 1965), pp. 792-808;
George H. Quester, Offenseand Defensein theInternational
System(New York: Wiley,1977); and
Sean M. Lynn-Jones,"Offense-DefenseTheory and Its Critics," SecurityStudies,Vol. 4, No. 4
(Summer 1995), pp. 660-691.
2. Importantcriticismsof the program can be found in JackS. Levy, "The Offensive/Defensive
Balance of MilitaryTechnology:A Theoreticaland HistoricalAnalysis,"International
StudiesQuarDeterrence(Ithaca,
terly,Vol. 28, No. 2 (June1984), pp. 219-238; JohnJ.Mearsheimer,Conventional
N.Y.: Cornell UniversityPress, 1983); JonathanShimshoni,"Technology,MilitaryAdvantage, and
International
World War I: A Case forMilitaryEntrepreneurship,"
Security,Vol. 15, No. 3 (Winter
1990/91),pp. 187-215; and Colin S. Gray, WeaponsDon't Make War: Policy,Strategy,
and Military
Technology
(Lawrence: UniversityPress of Kansas, 1993).
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International
Security23:3 | 190
ofoffense
VanEvera'sarticle,
arguingthathisconceptualization
I beginbyexamining
balancewiththe
dominanceas the "ease of conquest"confusesthe offense-defense
for
of successin war. This conceptualproblemhas seriousramifications
probability
I
and empiricalevidencehe bringsto bear in his theory.
hypotheses
theexplanatory
thenturnto Glaserand Kaufmann,notingthatwhile the authorsare cognizantof
withother
critiques,the theoristscannotavoid conflation
previousmethodological
oftheoffense-defense
theirbroaddefinition
Specifically,
variablesin theirframework.
to disis insufficient
balance,combinedwiththeirassumptionof "optimaldoctrine,"
I
Followingthesecritiques,
dominancefromeitherpoweror doctrine.
tinguishoffense
forempiricaltestingthatmighthelp
definitions
and suggestions
concludeby offering
problemsin futureresearch.
avoid thesemethodological
of War
The Ease ofConquestand theProbability
In "Offense,
Defense,and theCauses ofWar,"Van Everaarguesthat"war is farmore
balancehavea large
likelywhenconquestis easy,and thatshiftsin theoffense-defense
tenexplanatory
includingthetemphypotheses,
effect
on theriskof war."3He offers
linkhis
thatfurther
tationto strikefirstand increasedincentivesforexpansionism,
against
propositions
withoutbreaksof war.Aftertestingtheseexplanatory
definition
threeperiodsin history(Europe since 1789,ancientChina duringthe Springand
Autumnand WarringStatesperiods,and the UnitedStatessince 1789),Van Evera
explaining
ofa good theory,"
theoryhas theattributes
concludesthat"offense-defense
history
witha singlevariable.4
largeamountsof international
serious
arecompelling,
propositions
and empirical
Althoughmanyofthetheoretical
ofoffense
First,hisdefinition
flawsdetractfromVanEvera'sargument.
methodological
dominance-"conquestis easy"-conflatesoffensedominancewitha host of other
variables,mostnotablywiththebalanceofpower.Simplyput,VanEverahas defined
balance
theoffense-defense
offensedominancein termsof war outcomes,confusing
withtheprobability
statewillprevailin theeventofwar.5To say that
thatan attacking
of defeatingits opponentsays nothing,
an attackingstate has a high probability
and defensiveoperationsperse. One
of offensive
however,abouttherelativeefficacy
have an advantage,yetthe
can easilyimaginea scenarioin whichdefensivestrategies
attackingstateprevailsbecause of superiorlogisticalsupport,deepereconomicreadvantagein thenumberofforces.Forexample,conquest
sources,oran overwhelming
certainly
appeared"easy" fortheNorthat theclose of theAmericanCivilWar.This
but of the
versusdefensivestrategies,
of offensive
was nota function
of thestrength
In short,in orderto
greatersocial,economic,and logisticalsupportofthepopulation.6
3. Van Evera, "Offense,Defense, and the Causes of War,"p. 5.
4. Ibid., p. 41.
5. Also making this critiqueare Glaser and Kaufmann,"What Is the Offense-DefenseBalance?"
p. 70; however,I argue thattheytoo are vulnerable to these criticisms.
6. See Michael Howard, "The ForgottenDimensions of Strategy,"The Catusesof Warsand Other
Essays(Cambridge,Mass.: Harvard UniversityPress, 1983), pp. 101-115;and Theodore Ropp, War
in theModernWorld(New York:Collier Books, 1971), pp. 175-194.
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| 191
Correspondence
distinguish
theoffense-defense
balancefromthebalanceofpower,VanEveraneedsto
in relativeterms(i.e.,thevalue of attacking
casthis definition
comparedto thevalue
ofdefending),
ratherthanfocuson theabsolutevalue ofattacking
fora state.
Theseconceptualproblemsarecompoundedin VanEvera'sexplanatory
hypotheses.
Forinstance,
he assertsthat"whenconquestis easy,aggression
is morealluring:itcosts
less to attemptand succeedsmoreoften."7
Therefore
"resourcesare morecumulative
whenconquestis easy.... As a result,gainsare moreadditive."8It maybe thecase
thatconquestsareself-reinforcing;
however,
thishypothesis
cannotlogicallybe derived
froman assessment
ofoffensive
and defensive
strategies.
Althoughtheoffense-defense
balancecan tellus therelativecostsofattacking
versusdefending,
itmeasuresneither
theabsoluteprobability
ofsuccessnortheabsolutevalue ofconquest.
Furthermore,
Van Evera's causal explanationscome close to tautologies:it often
seemshe is arguingthatwhen conquestis easy or perceivedto be easy,stateswill
attempt
toconquer.Indeed,myriadvariables-including
statebehavior-aresubsumed
in his conceptualization.
Accordingto Van Evera,"Militarytechnology
and doctrine,
nationalsocialstructure,
and diplomaticarrangements
defengeography,
(specifically,
sive alliancesand balancingbehaviorby offshore
powers)all matter"in determining
the offense-defense
balance.9One is leftwonderingwhat factorscould be excluded
fromthis definition
to show the causal autonomyof the offense-defense
balance.
Moreover,
aftersubsumingall ofthesebehavioralvariablesintohis conceptualization,
he usestheoffense-defense
balancetoexplainbehavioramongstates.Forinstance,
after
theCrimeanWar"thepowerofdefenders
felldramatically
becausedefense-enhancing
diplomacylargelybrokedown."10In theend,VanEverais usingthebehaviorofstates
defensivealliancesin favorofoffensive
(eschewing
diplomacy)to explainthebehavior
ofstates(offensive
diplomacyuntil1871).11
thesemethodological
Finally,
flawsare strikingly
evidentin his empiricalaccounts.
theoffense-defense
Mostimportant,
Van Everamakesno attemptto avoid conflating
balancewiththe balance of power or militaryforces.For example,he arguesthat
as a resultof France's
"during1792-1815the offensewas fairlystrongmilitarily,
of theFrenchgovernment)."'12
adoptionof themass army(enabledby thepopularity
Althoughit is certainly
plausiblethatNapoleonicdoctrineand tacticsrelatedto mass
thesize of thearmyitselfis indeterminate
armiesfavoredtheoffense,
of theoffensedefensebalance. Arguably,
Napoleon'smass armywould have been moreeffective
defending
Frenchsoil,ratherthansearchingout offensive
campaignsacrossEurope.'3
7. Van Evera, "Offense,Defense, and the Causes of War,"p. 7.
8. Ibid., p. 8.
9. Ibid., p. 6.
10. Ibid., p. 28.
11. Van Evera avoided this tautologyin "The Cult of the Offensiveand the Origins of the First
WorldWar,"Internatioital
Security,
Vol. 9, No. 1 (Summer 1984), pp. 58-107. In thisarticle,alliances
are a clearlydistinguisheddependent variable. The independentvariable is perceptionof offense
dominance,and thus Van Evera does not incorporatestates' behavior into his explanation.
12. Van Evera, "Offense,Defense, and the Causes of War," p. 26.
13. For an example of this argument,see Jean Jaures,L'arin&enouvelle(Paris: Editions Sociales,
1977).
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International
Security23:3 | 192
ThatFrancecoulddeploya massarmytellsus a lotaboutthepowerofthecentralized
state,butverylittleabouttheoffense-defense
balance.
In sum,whileVan Everaarguesthatoffense-defense
theoryoffers
bothuniqueand
plausiblepredictions,
methodological
flawswithhis approachunderminethisclaim.
Bysubsumingpower,military
skill,diplomacy,
doctrine,
socialstructure,
and domestic
politicalstructure
intohis conceptualization
oftheoffense-defense
balance,VanEvera
cannotarguethattheoffense-defense
balancehas moreexplanatory
powerthananyof
thesevariablestakenseparately.Needless to say,a much narrowerdefinition
and
systematic
hypotheses
arenecessarybeforetheseclaimsto progresscan be empirically
tested.
TheOffense-Defense
Power,Skill,and Strategy:
Balanceand theOptimality
Assumption
In "WhatIs theOffense-Defense
Balanceand Can We MeasureIt?"Glaserand Kaufmannare particularly
concernedwithpreviousmethodological
critiquesof offensedefensetheory.
Theynotethatcriticshave questionedtheutilityof thetheoryon the
and that"thetheory
groundsthat"thefoundations
ofthetheoryareunderdeveloped"
containsinherent
balance
flaws,themostseriousof whichis thattheoffense-defense
14 In responseto
cannotbe measuredbecausetheoutcomesof war are so uncertain."
thesecriticisms,
Glaserand Kaufmann
statethattheoffense-defense
balanceshouldbe
definedrelatively:
"theratioof thecostof theforcesthattheattackerrequiresto take
15 Theyarguethatthisdefinition,
to thecostof thedefender's
territory
forces."
combinedwithsix keyassumptions,
allows offense-defense
theorists
to avoid conflation
withothervariables.Moreover,
thetheorists
balance
contendthattheoffense-defense
can be measuredby using the analyticaltoolboxof militarynet assessment,thus
allowingempiricaltestsof thetheory.
theoffense-defense
balancefromotherfactors
is a crucialtask
Clearly,
distinguishing
forGlaserand Kaufmann.Theystatethatthey"envisionoffense-defense
theoryas a
partialtheoryofmilitary
capabilities.... A morecompletetheorywould includetwo
additionalvariables:(1) power,measuredin termsofrelativeresources;and (2) what
we term'military
techskill,'thatis, a country's
abilityto effectively
employmilitary
balance
nology."'16
Indeed,Glaserand Kaufmanndo notclaimthattheoffense-defense
is theonlyorevenprimary
determinant
ofmilitary
butrather"eachofthese
outcomes,
threevariableshas thepotentialto overwhelm
theothersin certaincircumstances."17
theoffense-defense
balAlthoughGlaserand Kaufmannrealizethatdistinguishing
ancefrompowerand skillis important,
theyfailto do so adequatelyin theirmethodoofthebalancesubsumes
logicalframework.
First,theiradoptionofa broaddefinition
suchas forcesize and evennationalism.
competing
factors,
Althoughtheseare critical
in determining
theoutcomeofa war,theyaremorelikelyreflective
factors
ofthepower
14.
15.
16.
17.
Glaser and Kaufmann,"What Is the Offense-DefenseBalance?" p. 45.
Ibid., p. 46.
Ibid., pp. 48-49.
Ibid., p. 49.
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| 193
Correspondence
of a centralized
state,and theabilityof thestateto effectively
mobilizeresourcesand
and defensivestrategies.
forces,thantheyare of therelativeefficacy
of offensive
As I
argueabove,it is plausiblethatan attacking
statewithpopularsupportand a mass
armywilldefeata country
lackingtheseattributes.
This,however,does nottellus the
relativevalue ofoffensive
and defensivestrategies
foreitheroftheactorsinvolved.
Glaserand Kaufmannfacesimilarmethodological
to distinproblemswhentrying
guishthe offense-defense
balance frommilitary
skill.Theyargue that"the offensedefensebalanceshouldbe assessedassumingoptimality-that
is,countries
choosethe
best possiblestrategiesand forceposturesforattackand defense.Offense-defense
theoryrequiresthisassumption
becauseitfocuseson theeffects
oftheconstraints
and
The problemwiththis
environment."18
opportunities
presentedby the international
is thatitinvariably
leads to a posthoc,ergopropter
hocfallacy-wecan only
assumption
ascertaintheoptimalstrategy
afterobserving
whichstrategies
succeededduringa war.
By measuringthebalancein termsof successfulstrategies,
we can neitherdetermine
thebalanceex antenorsatisfactorily
separatethebalancefrompowerand skill.
Forinstance,
considertheoffense-defense
balanceduringWorldWarI. Mostwould
concurthatthebalanceheavilyfavoredthedefense,bothbeforeand duringthewar,
althoughthisbalance was misperceivedby statesmenand militaryleaders alike.19
thisdefensiveadvantageis epitomizedby the1916Battleon theSomme,an
Militarily,
attacklaunchedby theBritishon July1, 1916,and lastingthroughNovemberof that
sameyear.Overthisfive-month
span,and at a costofapproximately
500,000casualties
(thelargestnumbereverof Britishcasualtiesin battle),theBritishwereable to move
thefront
onlysevenmiles.Two yearslater,however,on March21, 1918,theGermans
achieveda massivebreakthrough
on thesameterrain,
usingthesametypeofweapons
availableto the Britishin 1916.Afterbreakingthroughthejunctureof Frenchand
British
troops,theGermansemployeda creepingbarrageand infiltration
tacticsto gain
140squaremiles)thantheBritish
moregroundon thefirst
dayofattack(approximately
had in 140 days.The Germanstrategy
in WorldWarI would therefore
be considered
In fact,usingthesecriteria
would
byGlaserand Kaufmannto be theoptimaldoctrine.
meanthatWorldWarI was "objectively"
offense
dominant.20
18. Ibid., p. 46.
19. Advancing the hypothesisthatdefense was dominantbeforeand duringWorld War I are Van
Evera, "Offense,Defense, and the Causes of War"; Glaser and Kaufmann,"What Is the OffenseDefense Balance?"; Van Evera, "The Cult of the Offensiveand theOriginsof the FirstWorldWar";
and Snyder,Ideologyof the Offensive.For a dissenting argument,see Shimshoni, "Technology,
MilitaryAdvantage, and World War I." For a more limited critique,see Scott D. Sagan, "1914
Security,
Vol. 11, No. 2 (Fall 1986), pp. 151Revisited:Allies, Offense,and Instability,"
International
176.
20. Shimshoni, "Technology,Military Advantage, and World War I." Historians and political
scientistsalike have noted that had the SchlieffenPlan succeeded-and this is not a ridiculous
counterfactual-we would call World War I objectivelyoffensedominant.See Sagan, "1914 Revisited." For otherexamples of thisdebate,see L.C.F. Turner,"The Significanceof theSchlieffenPlan,"
in Paul M. Kennedy,ed., The WarPlans oftheGreatPowers,1880-1914 (Boston: Allen and Unwin,
1979), pp. 203-204; and Martin Van Crevald, SupplyingWar: LogisticsfromWallensteinto Patton
(Cambridge: Cambridge UniversityPress, 1977), p. 116. I thankWarnerR. Schillingand Daniel H.
Nexon forhelpfuldiscussions on this topic.
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International
Security
23:3 | 194
Althoughthisconclusionmayseembizarre,I have troubleseeinghow Glaserand
Kaufmann
wouldrefute
it.A possibleresponsemightbe thatwhilemyexamplefocuses
on tactics,theyclaimto measuretheoffense-defense
balanceat thestrategic
level of
conflict.
This argumentis problematic
fortwo reasons,however.First,as Glaserand
at one levelwill
Kaufmannnote,"a changethatshiftsthebalancein a givendirection
Therefore
"a change
usuallyalso shiftit in thesame directionat all higherlevels."21
thatmakestacticaloffenseharderwill usuallyalso makeoperationaloffenseharder,
whichin turnmakesstrategic
Indeed,tacticalinnovations
at
offense
moredifficult."22
levelsforthe
theSommein 1918made offense
easierat theoperationaland strategic
Furthermore,
even ifdistinguishing
tacticalfromstraGermans,and latertheAllies.23
possible,Glaserand Kauftegicshiftsin the offense-defense
balanceis theoretically
In fact,their
mannprovideinsufficient
guidanceon how thiscould be accomplished.
to measown netassessmenttechniques
calculations
relyon bothtacticaland strategic
ure theoffense-defense
balance.24
neithercontrolsfor
In sum, Glaserand Kaufmann'sassumptionof "optimality"
balance.Indeed,
military
skillnorallowsforex anteassessmentoftheoffense-defense
code periodsin termsof
theoptimality
assumptionmeansthatone would inherently
balancein termsof themostsuccessfulstrategy
skill,measuringthe offense-defense
employed.In further
research,
thisdilemmacouldbe addressedbyassumingsymmetis ultimately
an
symmetrical
ricaldoctrine.
Obviously,
whetherdoctrineis sufficiently
to comparethe
however,would allow theorists
empiricalquestion.This assumption,
forskilland doctrine.
ofoffensive
and defensivestrategies
whilecontrolling
efficacy
Conclusion
problems,the hyAlthoughoffense-defense
theoryis riddledwithmethodological
arebothempirically
plausibleand policyrelevant.
pothesesputforth
bythesetheorists
for
and scrutiny
The Van Everaand Glaserand Kaufmannarticlesdeserveattention
thesereasons.Criticalrevisionofthetheoryis clearlyin order;to thisend,I offertwo
suggestions.
of theoffense-defense
balancethatavoids subsumingpowerand
First,a definition
as theprobability
Thebalancecannotbe represented
doctrineneedsto be constructed.
and should not incorporate
the absolutevalue of an attack.An
of takingterritory,
is one thatdescribesoffensedominanceas a situationin
exampleofsucha definition
to attacka statethanitdoes to defend
whichitcostsless in termsoflivesand territory
costsmorein
defensedominancewould implythatattacking
againstit.Analogously,
thandefendingagainstan attack.The offense-defense
termsof lives and territory
betweenthetwo.Notonlyis thisparticular
balanceis represented
as thecostdifference
it says nothingabout
of thestrategies,
definition
a comparisonof therelativeefficacy
theultimateoutcomeofa war,and thusavoids incorporating
powerintotheconcept.
21.
22.
23.
24.
Glaser and Kaufmann,"What Is the Offense-DefenseBalance?" p. 73.
Ibid.
Ropp, Warin theModernWorld,p. 267.
Glaser and Kaufmann,"What Is the Offense-DefenseBalance?" p. 75.
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Correspondence
Moreover,thisconceptualization
allows thattheoffense-defense
balancemightvary
fromstateto state,giventhatit is framedin termsofa subjectiveutilityfunction.
Second,empiricaltestsof the offense-defense
balancemustbe farmorerigorous.
ordefensedominant
Codingperiodsas offense
bylookingat theoutcomesofwardoes
nottellus abouttheefficacy
ofstrategies
and couldeasilybe representative
ofbalanceof-powerfactors.To avoid this,one mightconsidercases where statesfaced the
witheach otheroveran extendedperiodof time.Findingtime
of conflict
possibility
periodsin whichthe offense-defense
balancevaried,whilepowerand doctrinewas
relatively
constant,
wouldbe difficult;
however,
thiswouldallowthevariablesofpower
and doctrineto be controlled.
-Stacie E. Goddard
New York,N.Y.
StephenVan EveraReplies:
JamesDavis, BernardFinel,and StacieGoddardraise a numberof questionsabout
offense-defense
HereI focuson threethatseemmostimportant,
theory.
address
briefly
fiveothers,and lettherestpass withoutcomment,
exceptto expressa generaldissent
fromtheirarguments.
canwe characterize
First,
specific
orforceposturesas defensive
military
technologies
or offensive?
Or is everything
dependenton thecontextofcombat?
BernardFineltakesthelatterview,arguingthat"theoffense-defense
balanceis ...
an outgrowth
ofstrategic
interaction."1
He muchoverstates
a good point.As he notes,
thecapacityofa military
forcecan dependon theforcesand strategies
ofitsopponent.
Some forcesare betterat attackthandefenseagainstsome opponents,whilebeing
betterat defensethanattackagainstothers.Butmanyforcesare inherently
optimized
foroffense
or defense,in a way thatappliesacrossopponents.
A securenucleardeterrent
Itmakesitsowneressentially
is fundamentally
defensive.
At thesame time,it cannotconquerotherstatesthatpossessa secure
unconquerable.
deterrent.
Thesefactsapplyregardlessoftheopponent'sstrategy.
The defensivecharacterofthenuclearrevolution,
whichstemsfromtheserealities,
is thedefining
feature
ofmoderninternational
relations.
It is thesinglemostimportant
aspectofpost-World
WarII and post-ColdWarinternational
affairs.
Becausenucleardeterrents
aredefensive,
forcesdesignedto counterthemareessentiallyoffensive.
These forcesincludeoffensive
strategic
nuclearcounterforce
systems
(e.g.,accurateintercontinental
ballisticmissilesand strategicantisubmarine
warfare
systems)and area ballisticmissiledefenses.
Modernguerrillawar has defendedmanycountriesand conquerednone. It is a
fundamentally
defensiveformofwarfare.
Stateswouldpose littlethreattoone another
ifall reliedon citizenguerrilladefenses.
The accuraterepeatingrifles,machineguns,barbedwire,railroads,and entrenchmentsof the westernfrontin WorldWar I were fundamentally
defensive,as the
1. Bernard I. Finel, "Taking Offense at Offense-DefenseTheory,"InternationalSecurity,Vol. 23,
No. 3 (Winter1998/99),p. 183.
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International
Security23:3 | 196
repeatedfailedoffensives
of 1914-17demonstrated.
Theywereeventuallyovercome:
first
by theGermaninfiltration
tacticsin 1918,and laterby Germanblitzkrieg
concepts
ofarmoredwar.Butforthreeyearstheygave dominanceto thedefense.
in military
Manyotherdevelopments
history
canbe characterized
thesameway.The
weaponryand tacticsof thelate MiddleAges in Europeadvantagedthedefense;the
gunpowderrevolution
thenovercametheseweaponsand tactics,
restoring
theoffense;
innovationsin fortification
by Vauban and othersrestoredthe defensein the late
seventeenth
century;
and Napoleonicwarfare
bypopularmassarmythenstrengthened
In thetwentieth
theoffense.
century,
Germanarmoredblitzkrieg
tacticsalso bolstered
theoffense.
Theeffects
ofthesemodesofwarfare
withthenature
variedonlymodestly
oftheiropposition.
Theyhad an inherent
to ease thedefenseor theoffense.
propensity
In sum, technologyand forceposturedo, on importantoccasions,have innate
defensiveor offensive
propertiesand implications.2
Nuclearweapons are the most
important
recentexample,buttheyare onlyone amongmany.
Second,does offense-defense
theorylack parsimony?Does it committhe sin of
explainingby complexifying?
Finelclaimsthatit does. Its independent
variable-theease of conquest-includes
factorsdrawn fromthe military,
diplomatic,geographic,and social spheres.These
factorsare,says Finel,a "vast,unrelatedgrabbag of conditionsand variables."The
use ofsuchan unwieldyvariableleads to a "verysignificant
loss in parsimony."3
Finelhas thingsbackward.Offense-defense
It
theoryis elegant.It is parsimonious.
ordersand thereby
a previously
disorderedmelangeofphenomena.
simplifies
To judgeFinel'scharge,we first
mustask:Whatis parsimony?
Whatprovidesit,and
whatdetractsfromit?
A theoryis notshownto lackparsimony
simplyby demonstrating
thatitsconcepts
includea diverserange of lesser-included
concepts,because this is trueof every
oflesserconcepts.Forexample,nationalpower
concept.All conceptsare aggregations
is a conceptthataggregatesnationalmilitary
power,economicpower,and thepower
to marshalallies.Butthinking
aboutstrategy
wouldbe morecomplicated,
notsimpler,
ifwe droppednationalpowerfromourlexiconand discussedonlyitscomponent
parts.
ofairpower,
ofnationalpower,is an aggregate
naval
Military
power,a maincomponent
power,and groundpower,as well as of materialresources,skill,and willpower.
Discussionwouldbe farharderifwe had to addressthesecomponents
each
separately
time militaryquestionswere at issue. Airpower,a componentof militarypower,
thequalityand quantityof air force
aggregatesthequalityand quantityof aircraft,
in turnis an aggregaand thequalityofairdoctrine.
The qualityofaircraft
personnel,
2. A good survey of the historyof the interactionof militarytechnology,geography,and the
offense-defense
balance is Charles L. Glaser and Chaim Kaufmann,"What Is the Offense-Defense
Balance and Can We Measure It?" International
Security,Vol. 22, No. 4 (Spring 1998), pp. 44-82 at
61-66.
3. Finel, "Taking Offense at Offense-DefenseTheory," pp. 187, 188. Stacie Goddard likewise
complains that"myriad variables" are subsumed in my definitionof the offense-defense
balance.
"One is leftwondering what factorscould be excluded fromthis definition."Goddard, "Taking
Offenseat Offense-DefenseTheory,"International
Security,
Vol. 23, No. 3 (Winter1998/99),p. 191.
Arguing in the same vein are Glaser and Kaufmann, "What Is the Offense-DefenseBalance?"
pp. 60, 68-70.
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| 197
Correspondence
avionics,
tionof the speed, range,payload,maneuverability,
stealthycharacteristics,
At everylevel,we findthatconceptsare composedof
and durability
of theaircraft.
moreconceptsfromthelevelbelow.
useful.
My ruleofthumbis tojudgenew conceptsbyaskingiftheyare theoretically
In politicalsciencethisstandardusuallyrequiresthatconceptssomehowcorrespond
to phenomenain thereal world.Theymustfittheway thingswork,or theway we
think.A conceptthatfailsto do thisis artificial
and onlycluttersdiscussion.But a
discussion.
conceptthatcombinesotherconceptswhilealso capturing
realitysimplifies
Whenconsidering
leadersoftenaskifotherscanconquer
nationalsecurity
problems,
themor iftheycan conquerothers.Thesequestionslie at thecoreof manypast and
presentforeignand securitypolicydebates.And in askingif conquestis possible,
leadersaggregatethesame military,
diplomatic,
geographic,
and social factorsthatI
aggregateto capturethe ease of conquest.Leaders aggregatebecause theymust;
becausethesefactors
together
decideiftheycan conquerorbe conquered.Aggregation
is not easy and cannotbe precise,but leadersdo it because otherwisetheycannot
understand
theirnationalsecurity
situation.
As Bismarck
plannedhis warsofGerman
he recurrently
unification,
askedifGermanywas in a positionto wage aggressivewar
and geographicconsidTo answer,he had to weighmilitary,
successfully.
diplomatic,
erationsin some combination.
Later,Germanswho warnedof Germaninsecurity
weighedthesesame factorstogether.
Americansdid the same when assessingtheir
nationalsecurity
duringtheCold War.FormerPresident
HerbertHooveropposedthe
U.S. troopdeployment
to Europein 1951becausehe thoughtconquestwas difficult:
"This Hemispherecan be defendedfromCommunistarmiescome what will. ...
Communist
armiescan no moregetto Washington
thanany allied armiescan getto
Moscow."4 Hoover had to aggregate military,geographic, and diplomatic factorsto
reachthisconclusion.
theauthorsofNSC-68fearedin 1950thattheUnited
Oppositely,
in large partbecause theybelievedthat
Statesfaceda grave threatto its security,
both military
and
conquestwas easy.They reachedthisconclusionby aggregating
diplomaticfactors.5
think.
The conceptof ease of conquest,then,corresponds
to theway policymakers
It capturestheway theyorganizetheworld.Ifit did not,it wouldbe a complicating
distraction.
But it does. And in so doing,it simplifiesour discussionof security
problemsand policies.
Offense-defense
as well.It arguesthata number
theoryachievesothersimplicities
of important
war causes-expansionism,fierceresistanceto others'expansion,firststrikeadvantages,windowsofopportunity
and vulnerability,
faitsaccomplis,negotiationfailures,secrecy,arms races,and "chain gaining"in alliances-thatwere once
4. Quoted in Hugh Ross, ed., The Cold War:Containment
and Its Critics(Chicago: Rand McNally,
1963), p. 17.
5. See NSC-68, excerptedin Thomas H. Etzold and JohnLewis Gaddis, eds., Containment:
Documentson AmericanPolicyand Strategy,1945-1950 (New York: Columbia UniversityPress, 1978),
pp. 414, 416 (suggestingthat nuclear weapons are offensive),and pp. 427, 430 (suggesting that
states tend to bandwagon with threats).Also relevantis p. 396, suggestingthatthe Soviet empire
was vulnerable to Westernoffensiveaction,foressentiallysocial reasons.
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International
Security23:3 | 198
viewedas independent
stemfroma singlecause.Thissimplifies
theproblemofpower
and war.We see thata numberof disparatedangersare fedby a singletaproot.
In short,offense-defense
theoryexplainsa wide rangeofphenomenawitha parsiit streamlines
Far fromcomplexifying,
our understanding
of the
moniousframework.
war problem.
testable?
Third,is offense-defense
theory
JamesDavis complainsthatmyformulation
to be tested.6
he
ofoffense-defense
theoryis too impreciseand incoherent
Specifically,
notesthatI considertwovariantsofoffense-defense
theory-anobjectivevariantand
fromthesetwo
a perceptualvariant-butI inferand testonlyone set of predictions
setofpredictions.
variants.Instead,he argues,eachvariantmusthave itsown distinct
Davis makesa good point,buthis conclusionis overdrawn.
He showsthatI failedto
explainmyself,but does not show thatoffense-defense
theoryis untestableor is
otherwiseflawed.
Letme clarify
theconfusion
thatDavis rightly
identifies.
Offense-defense
theoryhas
an objectiveand a perceptualvariant.The objectivevariantframestheeffects
of the
of the peractualoffense-defense
balance.The perceptualvariantframesthe effects
ceived offense-defense
balance.Boththeobjectiveand theperceivedoffense-defense
balancesare indicators
oftheother:theobjectiveoffense-defense
balanceinfluencesand thusindicates-theperceivedoffense-defense
balance;and theperceivedoffensedefensebalance is influenced
by-and thusindicates-theobjectiveoffense-defense
boththe objectiveand the perceptualvariantsof offense-defense
balance.Therefore
aboutthecorrelates
ofboththeobjectiveand theperceptual
theorymakepredictions
in myarticle,
thesetwosetsofpredictions
offering
offense-defense
balances.I conflated
a singleunifiedforecast
weredominant
abouthow thingswouldappeariftheoffense
I did thisbecauseitworksin thisinstance:
bothvariants
orifitwerebelieveddominant.
ofthetheorymakeparallelpredictions
We
aboutbothobjectiveand perceivedreality.
neednotdistinguish
theseforecasts
becausetheyareessentially
thesame.Twovariants
butnotin thiscase.
ofa theoryusuallyproducetwodivergent
setsofpredictions,
balances
Whatdo we concludewhen theobjectiveand perceivedoffense-defense
differ,
as in 1914,whenthe objectivebalancefavoredthedefenseand theperceived
balance favoredthe offense?Bothvariantsof the theorymake stronger
predictions
of theperceivedbalancethantheobjectivebalance,so teststhat
aboutthecorrelates
lookto theperceivedbalanceare stronger.
Forexample,in the1914case bothvariants
withwar,evenifobjecofoffense
dominanceshouldcorrelate
predictthatperceptions
tiverealitiesfavorthedefense.The perceptualvariantpredictsthissimplybecauseit
deals onlywiththe perceptions,
and puts the objectivebalanceaside. The objective
variantpredictsthisbecause the impactof the objectivebalance is translatedinto
outcomesthroughits effecton the perceivedbalance,as follows:objectiveoffensedefensebalance--->perceivedoffense-defense
balance--->outcomes.The hypothesis
on the right(perceivedoffense-defense
balance---> outcomes)should operateeven
when the hypothesison the left(objectiveoffense-defense
balance ---> perceived
6. JamesW. Davis, Jr.,"Taking Offenseat Offense-DefenseTheory,"International
Security,
Vol. 23,
No. 3 (Winter1998/99),pp. 179-182 at 180.
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Correspondence
I 199
offense-defense
balance) does not. Hence even the objective variant forecastsa more
certaincorrelationbetween perceptionsof offensedominance and war than between
objectiveoffensedominance and war.
I saved my readers this detail because I feared thattheireyes mightglaze over. But
I should have explained it,and Davis is rightto complain thatmy failureto explain is
confusing.He is wrong to claim, however, that offense-defensetheoryis somehow
flawed or untestable.I failed to explicate my logic, but I thinkthatlogic is sound.
I close with remarkson five othercriticismsmade by Davis, Finel, and Goddard.
Finel argues thatseizing territory
does not confervictoryin war.7He seems to think
I believe otherwise,but I agree with him. My view is that the seizing of territory
requiresvictory(not the otherway around). Clearly,withouta victoryof some kind it
is impossible to seize and hold anotherstate's territory.
Finel quarrels with my coding of the historyof militarytechnologyand strategy.He
doubts thatguerrillawar grew easier with the developmentof mass-producedmodem
small arms after1800, and that accurate repeating rifles,machine guns, and barbed
wire made frontalassaults more difficultin the late nineteenthand early twentieth
centuries.8In so arguing,he takes on many historiansin addition to myself.I concur,
however,thatsuch questions are not open-and-shut,and we need a detailed study of
the historyof the offense-defense
balance in warfareto help resolve such disputes.
Stacie Goddard argues that I failed to distinguishthe offense-defense
balance from
the balance of power.9 I certainlymeant to distinguish them, and believe I did. In
footnote1, I suggest thatthe offense-defense
balance could be measured by looking at
the probabilitythat a determinedaggressor could conquer a targetstate with comparable resources. In other words, this measure asks how oftenconquest occurs where
the balance of power cannot account forthe outcome,because the winner startswith
no marked resource advantage. It should be clear fromthis that I am not running
togetherthe offense-defense
balance and the balance of power.
Goddard and Davis contend thatI use the behavior of states to explain the behavior
of states.10I plead guilty.In fact,the behavior of states oftenexplains the behavior of
states. Europe's continentalpowers reach for hegemony when Europe's offshorebalancers (Britainand the United States) are in an isolationistmood, and are more cautious
when the balancers are active. If that's how the world works, shouldn't we say so? I
don't see a problem.
Davis objects that I define termsin ways that will confineothers'analyses.1"But of
course othersare freeto adopt the definitionthatbest helps them answer theirquestions,just as I did. I cannot stop them and would not want to.
7. Finel,"Taking Offenseat Offense-DefenseTheory,"p. 184.
8. Ibid., pp. 184-185.
9. Goddard, "Taking Offenseat Offense-DefenseTheory,"pp. 189-190.
10. Ibid., p. 191; and Davis, "Taking Offenseat Offense-DefenseTheory,"p. 180.
11. Davis, "Taking Offenseat Offense-DefenseTheory,"pp. 179-180. Davis's claim thatI deviate
fromRobertJervis'sdefinitionof the offense-defense
balance by includingdiplomacy also seems
questionable.Jervis,like me, does mentiona diplomaticfactor-collectivesecuritysystems-as an
elementthataffectsthe securityof states.Jervis,"Cooperation under theSecurityDilemma," World
Politics,Vol. 30, No. 2 (January1978), pp. 167-214 at 176.
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Security23:3 | 200
International
attenissuesthatdeservefurther
Davis, Finel,and Goddardhave raisedimportant
theorystandsup to theircriticisms.
tion,butoffense-defense
-StephenVanEvera
Massachusetts
Cambridge,
Reply:
CharlesL. GlaserandChaimKaufmann
to respondto theissues raisedby BernardFineland
We appreciatetheopportunity
betweenus and
Stacie Goddard.We believe thatthereis littlereal disagreement
but on some pointsapparent
Goddard-she makes a numberof sound arguments,
of our
betweenher positionand ours resultfromher misunderstanding
differences
oftheentireoffensewe thinkthatFinel'swholesalecondemnation
views.In contrast,
both
based on failuresto understand
defenseresearchprogramis at leastpremature,
fortestingit.Goddard's
theoryand therequirements
thepurposesof offense-defense
theoryas a
and Finel'smostimportant
pointsrelateto thestatusof offense-defense
and
behavior.Therefore
we addresstheseissuesfirst,
structural
theoryofinternational
thenturnto severalseparateissuesraisedby one or theothercorrespondent.
to predictstates'behaviorby
theoryattempts
offense-defense
theory,
As a structural
Imporby theirenvironment.
presented
and opportunities
focusingon theconstraints
of resources
balanceand thedistribution
tantconstraints
includetheoffense-defense
(power),whileamongthechoicesthatthetheoryseeksto predictare decisionsabout
wars.
to formalliancesand fight
doctrine
and forceposture,as wellas whether
military
variouskindsof conStructural
theoriesof international
politicscan incorporate
as definedbyKenneth
thanothers.Systemstructure,
someofwhicharestricter
straints,
Waltz,excludespropertiesof units (typicallystates).In Waltz'snarrowdefinition,
thatemergefromtherelationships
oftheunitsto
structure
consistsonlyofproperties
forexamanarchy,
one anotherand thatno individualstatecan change-international
of
thatemergefrompurelymaterialfacts,whichcan be properties
ple.1Constraints
with
statesbut whichstatescannotchangeor evade, we can call materialstructure;
and weatherwouldqualify.
Theoriesbasedon thesehard
limitedexceptions,
geography
becausetheymisstoo muchof interest
constraints
are,however,oftennotsatisfying,
in mostareasofinternational
behavior.
that
of structure
employa "softer"definition
Most structural
theoriestherefore
thatstatescannotchangeor evade withinthetimescalesthey
includesanyconstraints
are likelyto considerin planning foreignand defensepolicy.2These may include social
at a
achievement
or its level of scientific
factssuch as a state'sformof government
ofpower,forexample,mustincludenotonlya state'spurely
giventime.Measurements
resourcesfrom
butalso thecapacityofthestateapparatusto extract
materialresources
Politics(Reading, Mass.: Addison-Wesley,1979).
1. KennethN. Waltz, TheoryofInternational
2. Appropriatetime scales fordifferenttypes of foreignpolicy decisions may vary.For offensedefense theory,which is principallyconcernedwith understandingdecisions in peacetime about
planning fordeterrenceor forfightingfuturewars, we thinka relevanttime scale is oftenfrom
several years to ten years, although there could be variations-for example, if a state could be
highlyconfidentthatit would face no threatsfora longer period.
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| 201
Correspondence
use. Our measureoftheoffense-defense
societyformilitary
balanceincludeswhether
thestate-and its adversaries-arenation-states
or multinational
empires,as well as
manyaspectsof technology.3
Includingcertainunit-levelfactorsdoes not erase the
difference
betweenstructural
and nonstructural
theories.Whatall structural
theories
excludeareexplanations
oftheactualdecisionmaking
process,includingthepossibility
of flawsof perception
and judgment,
and information
aboutstatepreferences
thatis
based on theirunit-level
characteristics.
To understandthe impactof constraints,
structural
theories,includingoffensedefensetheory,
mustassumethatstates'policychoicesarebroadlyoptimalor rational;
subjectto theconstraints
theyface,statesmakeeffective
policychoicesformaximizing
theirinterests.4
must includea theoryof
Theoriesthatdo not assume optimality
In such theoriesmuchof the explanationof state
suboptimalstatedecisionmaking.
behavioris oftenattributed
to domesticpoliticalcompetition
and/orto flawsin the
decisionmaking
process;theimpactof environmental
constraints
on policychoicesis
weakerand hardertoisolate(althoughthosesameconstraints
maystillexerta powerful
influence
on theeventualoutcomesofpolicychoices).
The optimality/rationality
assumptionin structural
theoriesis usefulin threeways:
itcanprovideguidanceformakingpolicy;itestablishes
a baselineagainstwhichstates'
whethertheyare flawed;and itcan helpassess
policiescan be comparedto determine
thelikelyimpactofflawedpolicies.Byproviding
a baseline,theoptimality
assumption
in offense-defense
theoryenablesus to separatemilitary
skillfromthebalance.The
balance is measuredassumingthatall countrieshave highlevels of military
skill.5
Choicesthatdivergefromthebaselineare suboptimaland indicatelow skill.
Goddardobjectsto our inclusionof an optimality
assumptionin offense-defense
skillfromthe offensetheory,
arguingthatit leaves us unable to separatemilitary
defensebalance.6The problem,as she sees it, is thatthe optimalstrategycan be
determined
whichstrategies
only"afterobserving
succeedduringa war,"whichmeans
thatwe cannotdeterminethebalanceex ante.We agreethatthebalanceshouldbe
measuredex ante-thisis requiredby thetheory.
Goddard'sobjectionis based on an
of the standardof optimality
She
exaggeration
requiredforpurposesof the theory.
takesoptimality
tomeantheabsolutebestchoicethestatecouldmakegiven
apparently
that
notjust the(limited)information
availableat thetimebut also theinformation
wouldbe providedby futureactions.Withthisunderstanding
it would
ofoptimality,
3. Constraintscould include factsthatdecisionmakerstheoreticallycould change,but only at costs
theywould likelyconsider unacceptable. For instance,a multinationalempire could convertitself
into a nation-stateby giving up its imperial territories
and subjects,but this would likelyviolate
the rulers'sense of the identityof the state,as well as reduce its resources.
4. Except in formalrationalchoice-orientedwork, the assumption is not usually thatactual state
decisionmakingprocesses meet normativestandardsof rationality,
but ratherthatdecisionmakers
act "sensibly": given the informationavailable to them,decisionmakersusually make choices that
do not vary much in substance fromthose thatwould be made by purely rationalactors.
5. Charles L. Glaser and Chaim Kaufmann,"What Is the Offense-DefenseBalance and Can We
Measure It?" International
Security,
Vol. 22, No. 4 (Spring 1998), pp. 44-82 at 55-56.
6. Stacie E. Goddard, "Taking Offenseat Offense-DefenseTheory,"International
Security,
Vol. 23,
No. 3 (Winter1998/99),pp. 193-194.
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International
Security23:3 | 202
cannotbe knownuntil
indeedfollowthatoptimalforceposture,doctrine,
and strategy
theyare revealedby war outcomes,and thatex ante measurement
of the offensedefensebalancewouldbe impossible.7
However,thisis notwhatwe meanbyoptimality;the standardthatwe employis thatstateschoose optimally"withinreasonable
availableto themat the time;to imposea
limitsof analysis"giventhe information
stricter
standardwouldbe unreasonable
fora theoryintendedto predictactualbehavior.8Our standardis thesame optimality/rationality
assumptionthatappearsin most
structuraltheories.9
Based on our understandingof structure,we also rejecttwo of Finel's key points.
balance is not a structuralvariable. Rather,it
First,he argues that"the offense-defense
can be influencedby immediatedecisions about deploymentsand employmentstrategies." This is incorrect.The offense-defense
balance is a constraint,not a measure of
the effectivenessof actual deployed forcesforeitheroffenseor defense. It answers the
question: How secure can statesbe, assuming thatboth theyand theiropponents make
optimal choices? The offense-defense
balance, in combinationwith power, determines
how well a state can do; state decisions in combination with structuralconstraints
determinehow well a state will actuallydo. Suboptimal decisions reduce the state's
militarycapability compared to the best that it could be, but do not influencethe
balance itself.10
For example,ifone state deploys nuclear weapons in vulnerablebasing
modes, thenan attacker'sprospectsforsignificantly
limitingdamage (and thereforefor
a successful offensiveattack) will be much greaterthan if the state had made better
balance forthis example remains
deploymentdecisions. However, the offense-defense
definedby the bestretaliatorycapabilitythat the state could achieve given both sides'
resourcesand available technology.
Second, Finel argues that the offense-defensebalance is not a structuralvariable
because it is an "outgrowth of strategicinteraction,"so that "the optimal choice
depends on the opponent's decisions.""1In response, we would firstlike to point out
thata greatmany militarypolicy decisions,especially at the levels of doctrineand force
posture,are pure optimizationproblemsinvolvingno interaction.BeforeWorld War I,
all armies would have been betteroffdeployingmore machine guns and less cavalryregardlessof what anyone else did. Between the two world wars,all navies would have
been betteroffinvestingless in battleships.Finel's observationthatancientarmies used
widely varyingforcecombinationsdoes not imply,as he suggests,that the best force
7. Actually,optimal strategyin Goddard's sense cannot be reliablydeterminedeven aftera war.
Ex post we know thatthe victor'schoices were successful,but not necessarilywhethertheywere
optimal.The victorcould have won despite suboptimalstrategybecause of even worse suboptimal
choices made by the loser. Alternatively,
even if the loser's choices were optimal and the victory
was the result of superior power, it is possible that the victorcould have succeeded even more
easily with a betterstrategythatwas not tried.
8. Glaser and Kaufmann,"What Is the Offense-DefenseBalance?" p. 55.
9. This does mean that when informationthat would affectstates' strategies is unavailable,
decisionmakers'estimatesof the offense-defense
balance may differfromtheestimatestheywould
have made had theyhad the additional information.A possible example is the difficulty
in 1939
of estimatingwhetheratomic weapons would be developed in time foruse in World War II.
10. Glaser and Kaufmann,"What Is the Offense-DefenseBalance?" p. 55.
11. BernardI. Finel,"TakingOffenseat Offense-DefenseTheory,"International
Security,
Vol. 23, No.
3 (Winter1998/99),pp. 183,184.
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| 203
Correspondence
posturegenerally
dependson theforcepostureoftheopponent.Nearlyall ofthemost
withlesserinvestment
ancientarmieswerebased on coresofheavyinfantry,
successful
in cavalryand lighttroops.Whenarmieswereorganizedon otherprinciples,
thiswas
orbyterrain,
notbythenature
usuallybecauseoflimitations
imposedbysocialsystems
notonlydoctrinal
but
oftheopponent'sarmy.Whenstructural
constraints
are strong,
choicescanbecomenoninteractive.
Forexample,at thestart
also somewartimestrategy
ofWorldWarI, all Europeanstateswouldhavebeenbetteroffiftheyhad scaleddown
theiroffensive
plans,regardlessofwhatotherstatesdid.
interactions
do occur.Whentheydo, whether
Finel'spointis validdepends
Strategic
would meanthat
on exactlywhatwe meanby "interaction."
One senseofinteraction
and strategies
notonlysubjectto those
each statemustoptimizeitsmilitary
doctrines
but also subjectto theknowledgethat
constraints
it directly,
structural
thatinfluence
theiropponentswill also be attempting
to optimizetheirown choicessubjectto the
balanceis estimatedassumingthatboth
constraints
facingthem.The offense-defense
sides do thebesttheycan,each knowingthattheotherside is also doingthebestit
can.Forexample,a stateattempting
to developan effective
nucleardamage-limitation
capability
againsta particular
opponentwould have to takeintoaccountnotonlythe
but also its
technical,
geographical,
and otherlimitson its counterforce
capabilities,
ofitsstrategic
forces.Ifmissile
thesurvivability
opponent'sbestoptionsforimproving
and the
accuracyis low,theopponentcan deploysurvivableforceswithlittleeffort,
balancewill strongly
favordefense.If accuracyis highand the opponentlacks the
forsurvivablelauncherssuch as mobilemissilesand nuclear-powered
technology
itwillhave to spendmuchmoreto achievea robustretaliatory
submarines,
capability,
In any case,theresulting
and thebalancewillbe morefavorableto offense.
measure
of the balance is fullystructurally
determined(providedthatstatesdo not make
tostructural
suboptimal
choices).To theextentthateachstaterespondsnotonlydirectly
butalso to theother'sbehavior,it is simplyincorporating
factors
additionalstructural
mediatedindirectly
effects
throughtheirpressureon theopponent.
A secondsenseof"interaction"
wouldbe a situationin whichstructural
constraints
exertonlya weak influenceon strategychoice,so thateach side has two or more
optionsthatare equallygood froma structural
pointof view,and thatare different
enoughfromeachotherthatthebestcounterstrategies
againsteacharequitedifferent.
Thussuccessforeach side would dependin largeparton correctly
guessingtheother
side's choice,but thereis no way to guess exceptby havingsome insightintothe
opponent's
decisionmaking
process,
orbyluck.In Finel'sterms,
thiswouldbe a true"rockwherethereis no oneoptimalchoice,whichwouldindeedmean
situation
scissors-paper"
thattheoffense-defense
balancecould notbe measuredexactly,
butwould spreadout
intoa band ofuncertainty
whosewidthwould reflect
theimpacton war outcomesof
different
combinations
ofa state'srightor wrongguessesaboutitsopponent'schoices.
Suchsituations
do occurin war,althoughtheyare morecommonat theoperational
and tacticallevels,whereindividualdecisionshave smallereffects
on finalwar outcomesthando choicesat thestrategic
and grandstrategic
levels.An examplemightbe
Germanattemptsin 1944 to estimatewhetherthe Alliedinvasionof Europewould
come at Normandyor Calais. Variousconstraints
effectively
ruled out sites either
further
westor east,but thisstilllefttheAllies(and thustheGermans)witha choice
to makebetweenthetworemaining
options.Had theGermansguessedcorrectly,
the
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International
Security23:3 | 204
Allies'1944-45campaignwould have been noticeably
moreexpensive,but it is quite
unlikely
thattheoutcomeofthewarwouldhavechangedorthatitslengthwouldhave
beenaffected
verymuch.By comparison,
strategic
and grandstrategic
choices,which
on war outcomes,are usuallyheavilyconstrained
can exertlargereffects
by factors
suchas geography;
states'political,social,and materialresourceendowments;
and so
forth.Therefore
strategicand grandstrategicchoicesare oftenmoresimilarto the
mutualoptimization
model discussedabove thantheyare to guessinggames. For
example,in WorldWarlI theAlliescould notdefeatGermanywithoutmovinghuge
fromtheUnitedStatestoEurope,and theironlypractical
amountsofmenand materiel
methodwas by sea. The Germans'mostefficient
methodofopposingthisflowwas by
submarine.Bothsides' plans took thesefactsinto account,but thiswas a mutual
nota problemofguessingtheother'sintentions.
optimization
problem,
Thus,although
interaction
whereourbestmeasureoftheoffense-defense
can createsituations
strategic
balancebecomesa band ratherthana point,it is notclearthatthesebands are often
wide.Thisis, however,a worthwhile
avenueforempiricalresearch.
Beyondthesepointsthatare closelyconnectedto theconceptofstructure,
Goddard
and Finel addresssome additionalimportant
points.First,Goddardarguesthatin
of the offense-defense
balanceby includingnationalism
adoptinga broad definition
and forcesize, we cannotseparatethe balance frompower,because thesefactors
influence
power.In fact,nationalismcan affectbothpower and the offense-defense
balance,in different
ways.As Goddardnotes,nationalism
can augmenta state'spower
itsabilityto extractresources.However,nationalism
by increasing
also affects
extractioncapabilitiesdifferentially,
themmorewhenthestateis trying
to protect
increasing
thatis understoodto be partofthenationalhomelandthanwhenit seeksto
territory
thatis notpartofthishomeland.Nationalism
taketerritory
makesiteasierto translate
aggregatepowerintotheabilityto defendthenationalgroup'shomeland.It makesit
harderto translate
thatis perceivedto be
powerintotheabilityto conquerterritory
intoour
outsidethenationalhomeland.Thisdifferential
effect
cannotbe incorporated
itis bestunderstood
standardnotionsofpower;rather,
as a shiftin theoffense-defense
balancein favorofdefense.
Goddardis correctthatforcesize can reflect
power,but it shouldalso be included
thebalance.Somestatessimplylacktheresourcesto
amongthefactorsthatinfluence
balancebestmatchedto
deployforcesofthesize thatwould createan offense-defense
theirgoals.Statesthendo thebesttheycan withtheresourcesavailable,thatis,within
theconstraints
thesize oftheirforces.For
imposedby theirpower,whichdetermines
forcesizeon thebalanceresultsfroman interaction
example,theimpactofconventional
betweenpowerand geography.
ratiostendto favordefensemore
High force-to-space
thando low force-to-space
ratios.As a result,twostateswhosemobilization
potential
is relatively
largein relationto lengthof frontwill facea balancemorein favorof
defensethanif both were weaker.For example,even if technology
had remained
thebalancebetweenGermanyand Francein 1914 would have been more
constant,
favorableto defensethanit was in 1870.Bothstateswere able to mobilizegreater
whichshiftedtheoffense-defense
resources,
balanceas wellas thebalanceofpower.If
we consideronlypower,we would predictthewrongimpacton theoutcomeofwar.
Althoughfromthe 1870s onwardGermany'spower grew fasterthan France's,its
chancesof conqueringFrancedeclined.We could have lumpedthiseffect
underthe
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Correspondence
| 205
butwe consideritimportant
enoughin itsown right
generalheadingof"geography,"
to mentionseparately.12
balancecannotbe measured:
A mainthemeofFinel'sletteris thattheoffense-defense
thebalancecannotbe reliablycoded,and theresultsof war
thefactorsthatinfluence
We agree withFinel thatwhetherthe balance can be
games are not reproducible.
whythe
In ourarticlewe explain,first,
ofthetheory.
measuredis centralto theutility
Also,
toolsof military
net assessmentare well matchedto measuringthebalance.13
we stressthatour articledoes notsettlethe
althoughwe offerreasonsforoptimism,
questionof how closelythebalancecan be measured.In fact,thearticleconcludesby
callingforresearchinto whethernet assessmenthas been feasiblein the past and
improved.Second,our articleexwhethernet assessmenttechniquescan be further
even whennet
theorycan oftenmakeusefulpredictions
plainshow offense-defense
about the value of the
assessmentis difficult
and therefore
substantialuncertainty
can
wouldbe tellingonlyifreliablenetassessment
balanceexists.ThusFinel'scriticism
neverbe done.To acceptFinel'spessimismwould mean,forexample,thatduringthe
Cold Warwe did notand could nothave had any real idea of Sovietprospectsfora
beforeWorld
on thecentralfront,
and thattheGermanmilitary
successfuloffensive
intheSchlieffen
WarI lackedtheanalyticresourcestodetecttheflawsand uncertainties
to thedebateby spelling
Plan. If Finelholds theseviews,he could have contributed
out whywe shouldacceptthem.
theory
becausehe saysitwrongly
Finelalso objectsto ourversionofoffense-defense
in war.Thiswouldindeed
as theprincipalmethodofvictory
treatsseizureofterritory
and thusestimates
oftheoffense-defense
be a mistake,
and wouldskewnetassessments
themeasure
balance-butthisis notourposition.Finelhas simplymisreadus,confusing
we treat
of successwiththemeansforachievingsuccess.For purposesof thetheory,
as themeasureofsuccessin waroutcomes(i.e.,
changesin politicalcontrolofterritory
A military
offensive
shouldbe considwe use thestandardClausewitziandefinition).
ereda successif,at theend ofthewar,politicalcontrolhas changedto theadvantage
has gainedfullorpartialcontrolofterritory
oftheattacker-either
becausetheattacker
it did not controlbefore,or because it has underminedan opponent'scontrolof
are (1) destrucmeansofachievingmilitary
victory
The twomostimportant
territory.14
theirabilityto contest
tionof enemyforcesor mobilizationpotential,undermining
thattheopponent
territorial
and (2) crediblethreats
ofsuchseverepunishment
control;
It is true,however,that
wouldratherconcedetheterritory
thancontinuetheconflict.15
12. Concern over nuclear proliferationillustratesa similar interactionbetween power and the
offense-defense
balance. Opponents of proliferationargue thatnew nuclear states will be unable
to build the large forcesrequired to provide adequate retaliatorycapabilities;as a result,although
nuclear weapons provided the superpowers with highlyeffectivedeterrentcapabilities,theywill
not do the same for small countries with limited resources. In other words, according to this
argument,the offense-defensebalance for these less powerful countries is more favorable to
offensethan it was forthe superpowers because these weaker countrieswill have smaller forces.
13. Glaser and Kaufmann,"What Is the Offense-DefenseBalance?" pp. 74-78.
14. Ibid., pp. 54-55.
15. There is some evidence that,at least in conventionalconflicts,punishmentis less likelyto be
decisive than is destructionof forces.RobertA. Pape, Bombingto Win:Air Powerand Coercionin
War(Ithaca, N.Y.: Cornell UniversityPress, 1996).
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International
Security23:3 | 206
who controls
certainterritories
duringa warcan sometimes
affect
victory
to theextent
thattheterritory
can be used to mobilizeadditionalcapabilities
withwhichto pursue
one or bothof theseapproaches.16Thus theoffense-defense
balance,whichis defined
as thecostofthemeansofvictory
relativeto thecostofthemeansofdenyingvictory,
reflects
theimpactofterritory
onlywhenit influences
war outcomes.
Finally,Finelarguesthateven if the offense-defense
balancecould be adequately
specifiedand measured,thecostin termsof complexity
would outweightheinsights
thatoffense-defense
theorycan provide.We agreethatmeasuringtheoffense-defense
balanceis complex.Nevertheless,
threepointssuggestthatFinelis againtoo negative.
First,
as we argueinourarticle,
keyvariablesinotherstructural
theories
ofinternational
relations,
suchas powerinbalance-of-power
theory,
also becomedifficult
to operationalize if we takethetaskseriously.
This is simplya generalproblemin international
relationstheory.
Second,as we discussin ourarticle,in cases wherecomplexity
makes
completenetassessmentintractable,
theirtaskwhilepreanalystscan oftensimplify
in theirestimate
ofthebalance.One possibility
servingreasonableconfidence
is tofocus
on particular
theaters
or campaignsthatare expectedto have a decisiveimpacton the
overallwar outcome.For example,in the 1980s,net assessmentsof a conventional
WorldWarIII in Europeconcentrated
on estimating
theprospectsof successof the
WarsawPact'sinitialoffensive
intoWestern
Europe.GivenNATO'smuchlargermobilizationpotentialand controlof theoceans,theWarsawPactcould nothope to wina
wariftheinitialoffensive
was notsuccessful.17
Third,and perhapsmostimportant,
the
predictions
madeby offensedefensetheoryoftendivergesignificantly
fromstandard
power-basedstructural
whichmeansthatiftheoffense-defense
theories,
balancecan
be measured,thepayoffis likelyto be worththeeffort.
In closing,we continueto believethatourarticlehas placedoffense-defense
theory
on a firmer
foundation.
Further
research
is warranted,
becauseoffense-defense
theorists
have establishedpowerfuldeductiveargumentsshowingthatpower alone is insufficient
to explainstatedecisionsaboutmilitary
and war,and that
forces,strategy,
offense-defense
variablesshouldinfluencethesedecisions.It is too earlyto rendera
verdictfromempiricaltestingof offense-defense
whichis stillin its infancy.
theory,
Further
testingis thekey.
-CharlesL. Glaser
Chicago,Illinois
-Chaim Kaufmann
Bethlehem,
Pennsylvania
16. See our discussion of cumulativityof resources:Glaser and Kaufmann,"What Is the OffenseDefense Balance?" pp. 67-68.
17. We discuss othertypes of simplificationsin our article;see ibid., p. 61.
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