The year 1943 saw the beginning of an unprecedented bombing campaign against Germany, as tens of thousands of RAF aircrews flew across the North Sea to drop bombs on German cities. They were opposed not only by the full force of the Luftwaffe, but by a nightmare of flak, treacherously icy conditions, and constant mechanical malfunction. Recounting the stories of these heroic crews who suffered appalling casualty rates, Kevin Wilson also salutes the scores of eager American pilots who—even before the attack on Pearl Harbor—travelled across the Canadian border to train with other future "Dambusters."