Political map of Europe & the Mediterranean 25 May 1940 (Blitzkrieg in the West): While the Allies (Allies of World War II) were still dealing with the fall of Denmark and Norway (Operation Weserubung), Germany struck west (Battle of France). The attack began with a German invasion of the Netherlands and northern Belgium. Then, as the Allied armies raced north to deal with this threat, the main German offensive smashed through the lightly defended hills of southern Belgium (Ardennes). The out-maneuvered British and French forces had been split in two.