The German invasion of Poland on September 1, 1939, marked the start of World War II in Europe. Germany’s blitzkrieg tactics overwhelmed the Polish forces, who were also facing an eastern invasion by the Soviet Union on September 17. Poland’s defeat and subsequent division between Germany and the Soviet Union, as per a secret protocol in the Molotov-Ribbentrop Pact, led to the loss of significant territory and population, and the start of a brutal occupation.