The attack on Nazi Germany’s dams on May 17, 1943, was one of the most remarkable feats in military history. The absurdly young men of the Royal Air Force’s 617 Squadron set forth in cold blood and darkness, without benefit of electronic aids, to fly lumbering heavy bombers straight and level towards a target at a height above the water less than the length of a bowling alley. Yet this story—and the later wartime experience of the 617 Squadron—has never been told in full.