In 1939 and 1940 the Nazi blitzkrieg crushed Poland and the Low Countries and France. This was a new type of warfare with air and ground forces working hand-in-glove and sweeping away all resistance. On the ground the new panzer divisions symbolised this combat revolution, and in the air its symbol was the all-conquering Luftwaffe with its fleets of Stuka dive bombers. When Hitler looked further...