HISTORY OF CONVOYS
BY
Bud Shortridge
Though of ancient origin, convoys - defined by the British official naval historian as ‘one
or more merchant ships sailing under the protection of one or more warships’ - were reintroduced
into modern maritime warfare by the British in 1917 and proved an effective counter-measure to
submarine attacks.
During the Second World War the convoy system was employed by all combatant nations
that had access to deep water, but Germany ran only coastal convoys, and what raw materials it
managed to obtain from the Far East were transported in Blockade runners. Italian convoys were
also coastal or trans-Mediterranean and a total of 4,385 were run to supply the Axis forces
fighting in the Western Desert and North African campaigns. This delivered 84.6% of the 2.84
million tons of supplies and fuel carried by them, a remarkable feat given that they were often
fiercely attacked and their escorts sustained high losses.
The third main Axis power, Japan, relied almost entirely on raw materials from overseas,
yet it woefully neglected its merchant fleet and the Japanese Navy, conditioned and trained to
take the offensive, made almost no preparations to protect it before war broke out in the Far East.
As a result, merchant ships sailed alone, or three or four would be escorted by one destroyer.
Sporadic, and largely unsuccessful, efforts were made to build sufficient escort vessels, but an
efficient shipping protection organization did not exist until the end of 1943; and it was not until
March 1944 that a proper convoy system, where between ten and twenty merchant ships were
adequately escorted, was introduced. This dramatically reduced losses and also increased the
losses of US submarines, but it came too late and by the end of the war 90% of Japanese
merchant shipping over 500 tons had been sunk.
The Allied situation was quite different: convoys, particularly those around which the
battle of the Atlantic was fought, were at the heart of their war effort. Broadly, they fell into
three main groups: regular ones which used the same assembly port; those mounted for ‘one/off’
operations such as the North African campaign landings; and the Operational Convoys for
troopship movements which seldom exceeded four ships, usually requisitioned passenger liners.
(The really fast liners such as the Queen Mary and Queen Elizabeth almost always sailed alone as
their speed was their best protection.) Each convoy route had a two-letter code such as “ON or
HX.” A third letter, “F, M”, or “S”, which signified its fast, medium, or slow components, was
also sometimes added as was the number of times that particular convoy had been run. On some
routes the number started again at 1 after 99 had been reached.
Early in the war westbound convoys were escorted only a certain distance into the
Atlantic before dispersing to sail independently to their destinations while their escorts made
rendevous with an eastbound convoy. But in May 1941, with Iceland in use as an Allied base,
convoys began to be escorted right across the Atlantic, through the mid-Atlantic air gap took
much longer to close.
Fast convoys often took evasive action by zigzagging, but slow ones rarely did so as it
caused too much confusion to the convoy. Instead, they sometimes took evasive courses,
changes of between 20 and 40 deg. From the correct course which were followed for a number of
hours. To combat air attacks, and to carry the long-range German Fock-Wulf Kondor aircraft
which acted as reconnaissance for the U-boats, makeshift efforts were made to give air cover
before escort carriers were introduced.
Initially, only ships which steamed between 9 and 15 knots (under 13 from November
1940 to June 1941) were put in convoy, the rest sailing independently, and it was among this
latter group that German auxiliary cruisers, U-boats, and German surface raiders claimed most of
their victims. With the exception of convoys attempting to break the siege of Malta during the
long drawn-out battle for the Mediterranean, the ratio of losses of independently routed ships to
those in convoy remained about 80:20 throughout the war, which showed just how effective the
convoy system was. Troop convoys were always given strong escorts, but early supply convoys
only had a single escort, often an armed merchant cruiser. Later, when U-boats became the main
menace in the Atlantic, it was calculated that the minimum number of escorts a convoy needed
was three, plus the number of ship in the convoy divided by ten. It was also found that doubling
the escort quadrupled U-boat losses for every ship sunk from that convoy, provided the escort
had no other duties. In late 1942 operational research calculated that larger convoys were
statistically safer than small ones, the perimeter of an 80-ship convoy being only one-seventh
longer than that of a 40-ship convoy. This revelation increased the size of convoys to such as
extent that in the summer of 1944 one group of 187 ships crossed the Atlantic.
Besides being involved in the vital Atlantic convoys, and in the essential Arctic convoys
to the USSR, the British ran crucial ones to sustain their position in the Middle East and the
Mediterranean. Before the fall of France in June 1940 the French Navy escorted the homeward
bound Gibraltar convoys and patrolled off the African coastline. However, when France
capitulated, and Axis air power and submarines had closed the Mediterranean to all but the
fastest British convoys, Freetown in Sierra Leone became an important assembly port and
command HQ for the regular “WS” convoys which had to use the long route via South Africa to
Suez. These convoys, codename with the initials of Churchill, the British prime minister who
had ordered the first in June 1940, took reinforcements and supplies for the troops fighting in the
Western Desert campaigns. Once Japan had entered the war the same codename was given to
high priority convoys destined for Singapore, Australia, and India.
Sometimes fast convoys through the Mediterranean had to be risked. Losses were highabout three times the rate in the Atlantic - and were invariably the occasion for fleet actions. One
which comprised five heavily escorted merchantmen took urgently needed tanks to the Middle
East in April 1942: another, the famous PEDESTAL convoy of August 1942, fought its way to
Malta. But of the 55 ships which sailed for Malta in convoy between August 1940 and August
1942, 22 were sunk, 11 forced to turn back, and only 22 arrived.
These statistics, and Malta’s desperate situation, encouraged the use of fast merchantmen
sailing alone. Unlike other convoy routes, this improved the odds, and of the 31 ships which
sailed independently during this time only nine were sunk and only one had to turn back. In May
1943, at the conclusion of the North African campaign, the Mediterranean was reopened to
normal Allied convoys. These were crucial to maintain the Sicilian and Italian campaigns, and
they were run at intervals of nine of ten days.
However, while the Mediterranean remained closed to all but the fastest ships, the
increased distance of sending the “WS” convoys via the Cape - from under 3,000 miles to nearly
13,000 miles stretched British shipping resources so much that in November 1941, when 20,000
troops needed conveying to the Fat East, there were no ships to transport them. The USA, then
still neutral, agreed to take them, and its entry into the war, and the construction in large
quantities of its Liberty Ships, gradually reduced the strain on British shipping resources.
When the USA first entered the war its navy was short of escorts ships. Though it could
have done so, it did not immediately adopt the convoy system off its eastern seaboard. Instead
the US Navy used patrols - including amateur ones to combat U-boat, and even employed Qships but 82 ships were lost between January and April 1942 along the eastern seaboard alone
before a partial convoy system, called the “bucket brigades”, was stated. Ships escorted by
whatever was available, made short daylight only inshore voyages to guarded anchorages. But
this incurred serious delays, sinking continued, and it was not until what was known as the
Interlocking Convoy System became operational that losses were drastically reduced. With this
system ships were run almost like trains. All “local” convoys were fed into two “express”
convoy routes, Key West - New York - Key West and Guantanamo - New York - Guantanamo
with the “express” convoys being timed to arrive at New York just before the departure of
Atlantic convoys. After it was first introduced, between Hampton Roads and Key West, on 14
May 1942, it was quickly extended in either direction. Instead, U-boats concentrated in the
Caribbean and the Gulf of Mexico, and between May and September 1942 they sank over a
million tons of shipping there, a statistic the official US naval historian merited printing in italic.
But by October the system had been extended into these areas, and to Brazil, and its efficiency
was soon proven by the fact that of the 9,064 ships which sailed in 527 of its convoys between 1
July and 7 December 1942 only 39, or less that 0.5% were sunk.
END