In the early hours of 1 September 1939, Hitler’s Panzers (tanks), supported by the Luftwaffe (air force), smashed over the border into Poland. They rapidly cut though Poland’s defences, thus making a path for the advancing infantry. This rapid and devastating method of fighting was known as Blitzkrieg or ‘lightning war’. Polish resistance was heroic, but ultimately futile. The USSR invaded from the east, as agreed...