Answer:
The European theatre of World War II opened with the German invasion of Poland on Friday September 1, 1939, which was then followed by the Soviet invasion of Poland on September 17, 1939. The Polish Army was defeated after approximately a month of fighting. Poland never officially capitulated. After Poland had been overrun, a government-in-exile (headquartered in Britain), armed forces, and an intelligence service were established outside of Poland. These organizations contributed to the Allied effort throughout the war. The Polish Army was recreated in the West, as well as in the East (after the German invasion of the Soviet Union).