Lance Mercereau

On this day in 1942, two British sailors swam to a sinking German submarine, climbed down inside it to grab its secret codebooks, and drowned when it suddenly plunged to the bottom, taking them with it. What they handed up through the hatch before they died helped turn the whole Battle of the Atlantic. This is the capture of U-559. To understand why it mattered so much, you have to understand how badly the war at sea was going. The German U-boats were strangling Britain, sinking merchant ships faster than they could be replaced, and the one thing that had let the Allies fight back was the ability to read the U-boats' secret radio messages, encoded on the famous Enigma cipher machines. But in early 1942 the Germans had added a fourth rotor to the Enigma machines used by their Atlantic submarines, and overnight the Allied codebreakers at Bletchley Park went blind. This new cipher, which the British called Shark, could not be broken. For most of 1942, the Allies could no longer read the U-boat signals, and the slaughter of their convoys grew terrible. The codebreakers knew that what they desperately needed was physical help, the actual codebooks from a captured U-boat, to find a way back into Shark. And on October 30, in the eastern Mediterranean, the chance came. A group of British destroyers hunting a submarine finally pinned down the U-559 and hammered her with depth charges for hours until, battered and leaking, she was forced to the surface. Her crew abandoned the sinking boat. Aboard the destroyer Petard, three men saw their opportunity and took it. A young officer, Anthony Fasson, and an able seaman, Colin Grazier, stripped off and swam through the dark water to the wallowing, half sunk submarine. They climbed down inside the flooding hull, into a cramped steel space that could become their tomb at any second, and began grabbing everything they could find, the secret documents and codebooks, and passing them up and out to a third man, a teenage canteen assistant named Tommy Brown, who ferried the material across to a boat. Among the papers they seized were the vital cipher documents the codebreakers needed. Then the U-boat, with no warning, suddenly filled and dropped. She plunged to the bottom of the Mediterranean, and Fasson and Grazier, still inside her, had no time to escape. They went down with the submarine and drowned, having just handed their country one of the most valuable prizes of the entire war. Tommy Brown, who had scrambled clear, survived. What those two men died to retrieve was exactly what Bletchley Park had been praying for. With the codebooks from U-559, the codebreakers found their way back into the four rotor Shark cipher, and before long they were once again reading the secret orders of the U-boat fleet. That knowledge let the Allies route their convoys around the waiting wolfpacks and send their hunters straight to the submarines, and it was one of the decisive factors in turning the Battle of the Atlantic in the Allies' favor over the following year. Fasson and Grazier were each awarded the George Cross, the highest British decoration for bravery away from the enemy's fire, both of them posthumously. Tommy Brown received a medal for gallantry too, and only afterward did it come out that he had been just sixteen years old, having lied about his age to join up. He himself would die not long after, in a fire while trying to save his little sister. Their story was so dramatic it was later turned into a Hollywood film, though the movie controversially made the heroes Americans. The truth was that it was two British sailors who gave their lives, swimming into a sinking submarine to steal its secrets, on this day in 1942, in one of the bravest and most important acts of the whole war at sea.