convoys

convoys. (See also Arctic convoys.) 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. These 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 (see Force K).

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 rendezvous 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, though 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° from the correct course which were followed for a number of hours. To combat air attacks, and to harry the long-range German Focke-Wulf Kondor aircraft which acted as reconnaissance for the U-boats, makeshift efforts were made to give air cover (see CAM ships, fighter catapult ships, and MAC ships), 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 (see below) 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 ships 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 1942operational 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 an 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 (HG) 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, codenamed 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 high—about three times the rate in the Atlantic—and were invariably the occasion for fleet actions. One (TIGER) 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 were 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 or 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 4,800 km. (3,000 mi.) to nearly 20,800 km. (13,000 mi.)—stretched British shipping resources so much that in November 1941, when 20,000 troops needed conveying to the Far 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 escort 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 (see Civil Air Patrol and Coastal Picket Patrol)—to combat U-boats, and even employed Q-ships, 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 started. Ships, escorted by whatever was available, made short daylight-only inshore voyages to guarded anchorages. But this incurred serious delays, sinkings continued, and it was not until what was known as the Interlocking Convoy System (see Map 23) 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 (KN–NK) and Guantanamo–New York–Guantanamo (GN–NG), 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 than 0.5%, were sunk.

Bibliography

Winton, J. , Convoy (London, 1983).