CONVOY  — Dr. Phil Judkins (University of Leeds). — 2nd August 2021

Britain is an island and, during the war, almost all mater­i­als coming in or going out of Britain had to go by sea. The Germans knew this and used their U-boats, E-boats and air­craft to isol­ate Britain.

The first WW2 ship to be sunk by tor­pedo was Athenia, but the Germans denied respons­ib­il­ity, prob­ably because they were afraid that the USA might join in the war. Mines were also used — con­tact mines which exploded if a ship hit them, and mag­netic mines which were triggered by the steel hulls of ships. Many British navy ships used ‘degauss­ing’, cur­rent passing through copper strips to make them non-magnetic, and many ships were tem­por­ar­ily made safe by “wiping” their hulls with an elec­tric coil. The Germans developed acous­tic mines which were exploded by the ship’s engine noise.  Minesweepers were used to remove the mines with, for acous­tic mines, a jack­ham­mer sus­pen­ded in a box under its keel whose noise exploded the mines at a safe dis­tance.

The first pro­tec­ted con­voys were for the “Coalscuttle Brigade”, slow, small, coastal coal ships which were pro­tec­ted by armed trawl­ers. In 1940 many ships of convoy ‘Peewit’ were sunk by E-boats and German bombers, show­ing that U-boats were not the only threats to ship­ping.

The S.S. Automedon was cap­tured by the Germans with, in its cargo, naval code­books, so the Germans could read where all British con­voys were headed. However, the British had man­aged to break the German ’Enigma’ code, which led to the sink­ing of the Bismarck. Breaking an ‘Enigma’ mes­sage would yield only a 100 square mile rect­angle con­tain­ing a U-boat, but new radar sets powered by a “cavity mag­net­ron” whose mag­nets were developed by research­ers at Sheffield University and made by Sheffield firms, enabled pre­cise search inside that rect­angle, while Asdic (sonar), in which a pulse amp­li­fier sends out a sound­wave under the sea and detects the echo from a U-boat, made the final pin­point­ing of the U-boat.

When America joined the war, it, did not at first use con­voys pro­tec­ted by war­ships.  Many tankers were sunk because they trav­elled in day­light, had all their lights burn­ing at night, or were sil­hou­et­ted against coastal illu­min­a­tions. Britain sent ships and air­craft to pro­tect American tankers.

Arctic Convoys first sailed in the Arctic winter during the long winter dark­ness, but later suffered heav­ily in the Arctic’s long summer days. In the Mediterranean in 1942 Malta was sur­roun­ded and run­ning out of fuel so the ‘Pedestal’ convoy, includ­ing air­craft car­ri­ers was sent, but German and Italian air­craft, E-boats and U-boats sank one car­rier, three cruis­ers and many freight­ers. The tanker ‘Ohio’, with a full load of fuel, was hit sev­eral times and split almost in two, but man­aged to reach Malta sand­wiched between two des­troy­ers. Ohio then dis­charged all her fuel before sink­ing!

Dr. Phil told us about many other con­voys, includ­ing the Atlantic convoy ONS5 where cen­ti­metric radar, using the mag­nets developed by Sheffield University, helped des­troy 13 U-boats which attacked the convoy. Those losses were unsus­tain­able, and the Germans with­drew U-boats from the Atlantic.

D-Day saw the largest convoy, 7,000 ves­sels pro­tec­ted by 1,200 war­ships of the Royal Navy and other navies, to carry British and American and other nation­al­it­ies’ troops to invade the French beaches.

There were about 1200 U-boats and 783 were sunk with others were dam­aged beyond repair.  After the war only 4 were pre­served intact.

Convoys were the import­ant way the war was won but it was by a very narrow margin and at a huge cost in human life.