Final answer:
Germany invaded Poland on September 1, 1939 to start World War 2 in Europe.
Step-by-step explanation:
Germany invaded Poland on September 1, 1939, to start World War 2 in Europe. This invasion is known as the German Invasion of Poland and it was a significant event that marked the beginning of the war. The invasion demonstrated the use of blitzkrieg tactics by the German troops, which combined air power and armored units to quickly overrun the Polish defenses.