After WWII, Europe was divided between the Western-aligned countries supported by the US and the Eastern bloc led by the Soviet Union. This division marked the beginning of the Cold War between the two superpowers. The US sought to contain the spread of communism through policies like the Truman Doctrine and Marshall Plan, which provided military and economic aid to countries resisting Soviet influence. In response, the Soviet Union established the Warsaw Pact for mutual defense of Eastern European communist states. Both NATO and the Warsaw Pact aimed to protect their members against potential aggression from the opposing alliance through military cooperation.