The correct answer is NATO.
The North Atlantic Treaty Organization is an alliance of 28 countries including the United States, most European Union members, Canada and Turkey.
The Treaty was signed on April 4, 1949.
NATO's primary purpose was to defend member nations from threats by communist countries.
After West Germany joined NATO, the communist countries formed the Warsaw Pact as they way to protect the areas under Soviet influence.
During the Cold War, NATO's mission expanded to prevent nuclear war.
