Soon after war broke out, Hitler's U-boats began to sever Allied lifelines. In the grey wasteland of the North Atlantic, submarines prowled; at night, the sky lit up with the flames of torpedoed and sinking merchant ships and tankers.
To meet the growing crisis, ingenious amateurs joined the nucleus of dedicated professionals at Bletchley Park. As the Battle of the Atlantic raged, they raced to unlock the continually changing German naval codes. Their mission: to read the U-boat messages of Hitler's cipher device, the Enigma.
Critical to their success was a series of raids at sea. U-110, captured intact in the mid-Atlantic, yielded an example of the Enigma machine itself - as well as a trove of secret documents. The weather ship Lauenburg, seized near the Arctic ice pack, provided code-settings for an entire month. In the Mediterranean, two sailors rescued a German weather cipher than enabled the team at Bletchley to solve the Enigma after a yearlong blackout.