In the summer of 1940 the Germans prepared to launch Operation Sea Lion, the invasion of England. The British, barely recovered from Dunkirk, rallied their defenses. Both sides operated in great secrecy and, because the invasion never took place, the dramatic preparations for what would have been one of the watershed battles of history faded from memory. Not, however, before Peter Fleming rescued this fascinating story from military archives and the recollections of survivors who…