Europe 1939-1941 By Sifven Sep 1, 1939 Hitler invades Poland nah Apr 30, 1940 Hitler invades Denmark and Norway May 10, 1940 Blitzkrieg Jun 11, 1940 Italy enters war on side of Axis powers Period: Jul 10, 1940 to Oct 31, 1940 Battle of Britain Dec 8, 1941 Britain and US declare war on Japan