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Germany invades Poland, inciting Poland’s allies Britain and France to declare war on Germany. -
Working in concert with Hitler, Soviet leader Joseph Stalin orders the invasion of Poland, securing a share of Polish territory. -
Warsaw surrenders to German troops. Poland holds out for another 9 days before capitulating. -
Germany invades Norway, ending a 6-month period of limited land operations called the “Phony War.” -
Winston Churchill replaces Neville Chamberlain as British Prime Minister. The same day, Germany invades Belgium. -
Paris falls to German forces. France capitulates 11 days later. -
Japan attacks Pearl Harbor, starting war with the US. Sensing weakness, Hitler declares war on America 4 days later.