Major Events During WW2 By zazlle Sep 1, 1939 Hitler Invading Poland Period: Sep 1, 1939 to Dec 1, 1941 History Timespan Sep 3, 1939 Great Britain Declares War On Germany Nov 1, 1939 The Winter War May 1, 1940 Hitler launches Blitzkrieg May 1, 1940 Hitler Invades Denmark And Norway Jun 1, 1940 Italy Enters War Under The Axis Power Jun 20, 1940 France Signs Armistice Agreement With Germany Sep 1, 1940 Tripartite Pact Oct 1, 1940 Battle Of Britain Jun 1, 1941 France Signs Armistice Agreement With Germany Dec 1, 1941 Japanese Bombing of Pearl Harbour