The organization established to counterbalance the spread of communism in Europe post-World War II is the North Atlantic Treaty Organization (NATO). Founded in 1949, NATO was created primarily as a collective defense alliance involving Western powers, particularly the United States and several Western European nations. The organization's aim was to provide mutual defense against potential Soviet aggression and extend security across Europe. The formation of NATO represented a significant shift in international relations and military alignment during the Cold War, solidifying the divide between Western democracies and Eastern communist states.