On the night of 13 October 1939, the Type VIIB U-boat U-47, on its second war patrol, penetrated the main Royal Navy base at Scapa Flow and sank the British battleship HMS Royal Oak. This legendary attack is remembered as one of the most audacious raids in the history of submarine warfare. In this remarkably detailed account, the author charts the full story of U-47, its commander, and crew. He also examines all the main events in each of U-47's ten war patrols, particularly the attack on Royal Oak, for which a number of important new conclusions are explored, and covers U-47's ultimate fate.