ARTICLE
TheNorthernBarrage
Historically,perhapsthenaval
disciplinemostrelatedtotheworkand
skillsofthehydrographerisnaval
minewarfare.Successful
implementationrequiresknowledgeof
theconfigurationofthebottominthe
areatobemined,localtidesand
currents,andrelativelyprecise
navigationtopositionmines,identify
minefields,andultimatelyremove
mines.Thelayingandsubsequent
sweepingofthegreatminefield
knownasthe‘NorthernBarrage’
duringWorldWarIisanearly
forgottenstorythatencompassed
cuttingedgetechnology,evolutionof
hydrographictechniques,and
significantcourage.
WhentheUnitedStatesenteredWorld
WarIinApril1917,theGermanUboatcampaignwasatitsheight.In
December1916,Germanybegan
sinkingmerchantvesselswithout
warningandtwomonthslater
announcedunrestrictedsubmarine
warfare.ByApril,Germanywas
sinkingshipsboundforEnglishand
Frenchportsattherateof800,000
tonspermonth.Ifallowedtocontinue
indefinitely,sucharatewould
potentiallystarveGreatBritaininto
submission.InMay1917,theUnitedStatesenteredthewar.Tocounterthe
submarinethreat,GreatBritainandtheUnitedStatesdevelopedaconvoysystem
thatwaspartiallyeffectiveinstemmingthelosses,buttheystillamountedto
450,000tonspermonth.Thiswasanunsustainablelossrateandwouldultimately
doomtheAlliedwareffortifallowedtocontinue.
Otheranti-submarinemeasureswerealsoinstitutedincludingarmingmerchant
vessels,formationofsquadronsofsubmarinehuntersequippedwith‘listening
devices’,aerialpatrolbyseaplanesandblimpsarmedwithdepthcharges,arming
ofdestroyersandothercraftwithvirtuallyunlimitedsuppliesofdepthcharges,
andminingofwatershabituallytraversedbyenemysubmarines.Thislast
measureisofgreatinteresttohydrographersasthegreatestcombatminingoperationuptothattimeinhistorywas
completedoverthenextyear.WiththecessationofhostilitiesinNovember1918,theproblemofremovingavastnumberof
minesandopeningsealanestotheshipsoftheworldbecameofparamountimportance.
DevelopingaPlan
Earlyon,theconceptofconfiningGermansubmarinestotheNorthSeawassuggestedbetweentheBritishAdmiraltyandthe
UnitedStatesNavy.Thiswouldrequireeithermines,nets,oracombinationofminesandnets,extendingfromScotlandto
Norwayonthenorth,theminimaldistancebeing230miles,andaminefieldextendingacrosstheEnglishChannelonthe
south.TheBritishhadalreadyhadunsatisfactoryexperiencewithnetssoitwasdecidedtouseonlyminesforblockadingthe
exitstotheAtlanticOceanfromtheNorthSea.
Atthetimethedecisionwasmade,theUnitedStateswasdevelopingafiringdeviceforminesthatwouldactivatewhena
submarinewaswithin100feetofamine.ThiscomparedtoBritishminesthatrequiredcontactforactivation.Thedifference
wassignificantasthenumberofminesrequiredwiththeAmericansystemwouldbeapproximately1/3thatrequiredwiththe
Britishsystemtoestablishatrulyeffectivebarrier.Itwasthisdifferencethatmadetheconceptfeasible.Thedecisionwas
madetoproduce100,000Americanmineswiththenewfiringmechanismalthoughithadneverbeencombattested.Theplan
wastohavetheseminesreadyforplantingbythespringof1918.Toimplementthisplanseparateminecomponentswere
assembledbyover500manufacturingfacilitiessuchthatnooneplantorindividualwouldunderstandtheendproduct.
Additionally,80,000,000feetofwireropeand30,000tonsofanchormaterialwouldhavetobeproduced.Besidesthis
industrialeffort,afleetoftwenty-foursmallcargovesselswasdedicatedtotransportingtheminecomponentsfromtheUS
toScotlandforfinalassembly,tenshipsweremodifiedforlayingthemines,and,lookingaheadtopeace,afleetof34
speciallydesignedminesweeperswouldhavetobebuiltasrapidlyaspossiblestartinginJuly1917.Duringthewhole
operation,onlyoneofthetwenty-fourcargovesselstransportingminesacrosstheNorthAtlanticwaslosttosubmarine
attackwith41menlost.
LayingtheBarrage
TheUSminesquadronconsistingoftwooldcruisersandeightconvertedmerchantmenbeganarrivinginScotlandinMay
1918.MineshadstilltobeassembledattheScottishbases,butby7June,3400hadbeenassembledandtheminelayers
proceededouttolaythefirstrowofmines–47mileslongwithminesatthreedifferentlevels.Locatingtheminefieldsboth
priortolayingofminesandduringrecoveryoperationswasdonebylayingoutbuoyarraysthatwerepositionedusingtautwireapparatusformeasuringdistancefromknownshorepointsandsextantobservationsofcelestialbodiesforlatitude.
Taut-wireuseforhorizontalpositioningofminefieldsisanexampleoftechnologymodifiedandusedbyhydrographic
surveyorsfollowingthewar.ByOctober1918,theNorthernBarrage,asitcametobecalled,wasfinished.CaptainReginald
Belknap,theminesquadroncommander,recalled:"AbarrierofhighexplosivesacrosstheNorthSea–10,000tonsofTNT-,
150shiploadsofit,spreadacrossanarea230mileslongby25mileswideandreachingfromnearthesurfaceto240feet
below–70,000anchoredmineseachcontaining300poundsofexplosive,sensitivetoatouch,barringthepassageof
GermansubmarinesbetweentheOrkneysandNorway–thiswasthefinalfivemonths’contributionoftheAmericanand
Britishminingforcestowardsbringingthewartoaclose."
SweepingtheBarrage–TheGreatestWire-dragOperation
ThesensitivefiringdeviceandnovelconstructionoftheAmericanmines,theattributesthatdictatedtheiruseinthebarrage,
nowmadesweepingadangerouspropositionatbest.Technicalproblemsassociatedwithsteelvesselssweepingthefield
weresolvedinthewinterof1918-1919whichmadeitfeasibletousethenewAmericanminesweepers.Inaddition,asrelated
bytheUSNavyhistoryofthisoperation,"Thewaterwasdeep,beyondallthecustomaryestimatesformineoperations;the
windswerestrong;theseaswererough;theatmosphericconditionsweresuchastomakevision,forthegreaterpartofthe
time,difficultifnotimpossible."Themethodusedtosweeptheminefieldswaswire-drag-amethodfirstusedasa
hydrographictool.Initiallydevelopedasadriftingrope-sweepbytheFrenchhydrographerJosephRenaudin1882,modified
byengineersoftheUSLakeSurveyforsweepingwithalineattachedbetweenboatsin1903,andthenadoptedandfurther
modifiedbytheUSCoastandGeodeticSurveyinasystemthatbecameknownaswire-drag,themethodconsistedoftowing
alinebetweentwovesselsbymeansofanarrangementofbuoys,kites,andweightstomaintainapre-setdepth.As
practicedinhydrographicsurveying,thedepthofsweepwassetatalevelthatwouldallowsafepassageofdeepestdraft
shippingassumedtooccurinthesweptarea.Buoysattachedtothesweepwirewereobservedbythesweepingboatsand
whenanobstructionwasencountered,thebuoyswouldaligninaV-shapedpatternasthesweepingboatsproceededahead.
TheapexoftheVwouldindicatethelocationoftheobstructionwhichwouldbecarefullysoundedoutforleastdepth.
TosafelysweeptheminesoftheNorthernBarrage,asystemwasdevelopedwherethreepairsofsweepingvesselswould
rundownasinglelineofmines.Thefirstpairwouldhaveitssweepsettocuttheantennasofthenear-surfaceminesand
explodethem;thesecondandthirdpairswouldhavetheirsweepssetsuchthattheywouldcutminemooringcablesandset
adriftanyminesnotexplodedbythefirstpair.Theminessetadriftweredetonatedbyriflefirefromasmallvessel(asub
chaser)thatfollowedbehindthesweepingvessels.Theworkwasexceedinglydangerousasrandomminesexplodedona
regularbasis,oftenfornoapparentreason.Occasionally,theexplosionofoneminewouldactivateasecond,termed
’countermining’intheofficialhistory.Sometimestheseexplosionswouldoccurinthevicinityofasweepingvessel.Mines
werealsofouledinthesweepingwireandtheassociatedkitescausingexplosionscloseaboardwhileretrievingwire.Damage
tominesweepersoccurredonaregularbasis.AFlowerclassBritishminesweeperwassunkbymineswiththelossof40men
whiletheyweresweepingtheirsegmentofthebarrage.Americanlosseswerelesssevere–lessthantenmenandonlyone
smallvesselsunkduringfivemonthsofsweeping.However,onesweeperwaspermanentlydisabledandanotherhadsix
monthsofshipyardrepairsfollowingacloseexplosion.
ResultsoftheSweepingEffort
Afterfivemonthsofsweeping,betweenMayandSeptember1919,theAmericancommanderon-sitedeclaredthesweeping
jobcompleted.Thisoperationinvolvedrelativelynewtechnologies–aformofwire-dragusedbythesweepersfrom
hydrographictechnologyandtaut-wirehorizontaldistancemeasurementwhichpassedfromtheminesweepingcommunityto
thehydrographiccommunityfollowingthewar.Adisturbingstatisticisthatofthe56,611mineslaidinareassweptbyUS
minesweepers,4,392explodedprematurely,andonly21,295wereaccountedforduringsweepingoperationsleavingover
halfunaccountedfor.Overthenextthreeyears,64mineswerefoundintheNorthAtlanticandplottedontheaccompanying
mapbyPrinceAlbertofMonaco.HowmanyvesselsencounteredminesintheyearsfollowingWorldWarIisunknown.A
2009publicationbytheUnitedStatesNavyProgramExecutiveOfficeLittoralandMineWarfareandtheExpeditionary
WarfareDirectoratestatedthat"minecountermeasuresvesselsparticipatingin…theKattegatandNorthSeafindand
destroyWorldWarIandII-eramines."Twenty-fiveyearsafterWorldWarIIanestimated2,000sensitiveinfluenceminesstill
remainedinthePacific.Giventhenatureofminewarfareandthestateofworldpolitics,itwouldnotbesurprisingifmanyof
thehydrographersreadingthistodayspendpartoftheircareerengagedinsomeformofmineneutralisationactivitiesbeit
foranon-goingwarorclearingshippinglanesafterthecessationofwarfare.Asafinalnote,byvariouscountsbetweenfour
andthirteenU-boatsweresunkbythebarrage,afactorcontributingtotheendoftheWorldWarI.
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