The document provides a summary of key events during World War II:
1) Germany invaded Poland on September 1, 1939, quickly defeating Poland through the use of Blitzkrieg tactics. Germany then invaded Denmark and Norway in April 1940 and used Blitzkrieg tactics to invade France in May 1940 through Belgium, bypassing the Maginot Line.
2) Britain survived Germany's planned invasion in 1940 thanks to the Royal Air Force prevailing over the Luftwaffe in the Battle of Britain during July-September 1940.
3) Britain depended on imports for resources but survived the German U-boat threat in the Battle of the Atlantic through 1942 by adopting convoy systems protected by radar-equipped ships