U-110 — a U-boat abandoned but afloat

In the spring of 1941, the Battle of the Atlantic was raging: the U-boats were decimating the convoys, and the Royal Navy most often did not know their positions, for lack of being able to read German communications enciphered by the Enigma machines. Cracking this code was the obsession of the codebreakers at Bletchley Park, who were cruelly short of authentic German material to that end.

On 9 May 1941, convoy OB 318, south of Greenland, was attacked by U-110 of Commander Fritz-Julius Lemp — the officer who had sunk the liner Athenia on the very first day of the war. Spotted, the U-boat was forced to the surface by the escorts' depth charges. The crew abandoned it, convinced it was sinking. But the submarine remained afloat.

The captain of the destroyer HMS Bulldog had to decide in a few minutes: ram and sink the enemy submarine, the normal reflex of anti-submarine warfare; or stay his hand and send a party to board her, at the risk of an explosion or scuttling, to try to seize what she contained. The window was narrow: U-110 could founder or be scuttled at any moment.