The North Atlantic Treaty Organization (NATO) was founded in 1949 after World War II as a military pact between nations in the northern hemisphere of the world (Europe, America, etc). In contrast to the League of Nations set up after World War I, NATO focuses on a joint military defense and had the United States at the forefront. At the time in 1949, the Soviet Union was gaining power, especially in struggling war-torn nations. NATO was set up to combat them and the Warsaw Pact, which was similar to NATO, only with communist nations. It's worth noting that NATO is a group of democratic nations, and was used in the Cold War to combat the spread of communism.