Germany, led by Hitler, began invading surrounding countries using the tactic of blitzkrieg ("lightning war") to quickly take their land, seeking lebensraum ("living space"). This eventually led to World War II when Germany attacked Poland in 1939. Germany allied with Italy and Japan to form the Axis Powers, opposed by the Allied forces of France, Great Britain, and later the United States. Hitler had also signed a non-aggression pact with Stalin but later betrayed this pact when Germany invaded the Soviet Union in 1941.