The acronym "NATO" stands for the North Atlantic Treaty Organization. Established in 1949, NATO is a military alliance formed primarily for mutual defense against aggression. It was created in the aftermath of World War II to promote stability in Europe and counter Soviet expansion during the Cold War. NATO member countries commit to mutual defense in response to an attack against any member. Over the years, NATO has expanded to include many Eastern European nations and has adapted its mission to address emerging security challenges.