By the close of 1942, Allied shipping losses in the Atlantic had reached a peak, with 1,006 ships sunk by U-boat wolfpacks that year. Many of them were destroyed in the Greenland Gap, the area of mid-Atlantic which was out of range of protective Allied air cover. The following year brought radical changes to the Allied tactical and strategic struggle against the U-boats, with new training, technology and weapons, culminating in a catastrophic month of destruction for the German U-boat fleet. The Kriegsmarine lost more boats during the month of May 1943 than in the entire year of 1941, prompting its senior officers and later historians to remember it as Black May.
‘Attack! Advance! Sink!’
On the first day of May 1943, the Kriegsmarine’s Oberkommando der Marine recorded a total of 134 submarines at sea. Of those, 118 were on station or deploying to rendezvous, with 58 boats in four battle groups already positioned in the North Atlantic. The U-boats had transited from bases on the French and Baltic coasts to gather as the largest submarine force assembled at sea. Their operational mission was to destroy the merchant fleets sailing in convoy to supply Britain from the United States and Canada, driven by the commander of the German U-boat arm Grand Admiral Karl Dönitz’s exhortation: “Angreifen! Ran! Versenken!” (“Attack! Advance! Sink!”)
Ranged against them were elements of the combined Allied navies supported by the formidable industrial base of the United States and RAF Coastal Command, which included British and Commonwealth aircrew manning a variety of anti-submarine aircraft. In the words of Sir John Slessor, appointed commander in chief Coastal Command in February 1943, these men were “fighting the elements as much as the enemy, but when the tense moment came, going in undaunted, going in at point-blank range against heavy fire, knowing full well that if they were shot down into the cruel sea, their chances of survival were slender”.
Adopting the Rudeltaktic, or wolfpack, devised by Dönitz, U-boats concentrated into patrol lines
