European military action that commenced when German forces opened fire on Polish occupied points in Danzig, Poland, instigating WW II, in the "early hours." By September 20, Poland was occupied by the enemy. Britain had pledged to support Poland and France had a mutual defense treaty with Poland. Within a few days, the British and French declared war on Germany. The invasion of Europe began 5/10/1940, 4:35 AM from Berlin. Read less