On this day in 1943, the head of the German Navy Karl Dönitz called off the Battle of Atlantic after his U-boats suffered a mauling from which they would never recover.
German submarines would return to attack Britain’s supply lines – the battle raged from the first day of the war in Europe to the last.
But never again would they threaten the sea lanes as they had done in the first 3½ years of World War 2 – and especially in the spring of 1943.
The convoy battles of March, April and May 1943 were the most sustained and costliest encounters of the war – firstly for the Allies, then for the Germans as the latter sought to strangle supplies vital to Britain’s war effort, and the Allied powers committed their technological and naval might to try to stop them.
March 1943 marked the Allies’ lowest ebb, culminating in the largest convoy battle of the war (HX229/SC122). Over four days, U-boats mauled the two convoys – heading for Britain from New York – sinking 22 merchant ships.
The Germans hailed it as “the greatest convoy battle of all time” – a terrible blow which saw nearly half a million tonnes of Allied shipping end up at the bottom of the Atlantic that March. An official Admiralty report subsequently concluded: “The Germans never came so near to disrupting communications between the New World and the Old as in the first twenty days of March 1943.”
A quarter of a million tonnes of shipping was destroyed by the U-boats in the following month, but losses were also rising: a dozen boats in March, 15 in April.
The crunch battle began at the end of the month and ran on into May. Thirty German submarines attempted to break through the screen of 16 escorts around convoy ONS5, bound for North America from the British Isles. Thirteen merchant vessels were sunk, but so too half a dozen U-boats.
The tide was turning, confirmed a fortnight later when Allied defences fought off sustained U-boat attacks, sinking three, damaging a fourth – and all without a single merchantman lost.
‘Black May’ as it became known left 34 U-boats at the bottom of the Atlantic – “a frightful total, which came as a hard and unexpected blow,” Dönitz wrote. These were losses he could not sustain. "We had lost the Battle of the Atlantic.” He ordered his boats to abandon the ocean – for now. They would return with renewed technology, but too late to affect the course of the battle.
“The battle,” the Royal Navy’s official historian Stephen Roskill wrote, “never again reached the same pitch of intensity, nor hung so delicately in the balance, as during the spring of 1943. It is therefore fair to claim that the victory marked one of the decisive stages of the war.“
