The North Atlantic Treaty Organization, also called the North Atlantic Alliance, is an intergovernmental military alliance between 30 member states, 28 of which are in Europe and the other 2 being part of North America NATO constitutes a system of collective security, whereby its independent member states agree to mutual defense in response to an attack by any external party. It was established during the Cold War in response to the threat posed by the Soviet Union. The alliance has remained in place since the end of the Cold War, and has been involved in military operations in the Balkans, the Middle East, South Asia, and Africa. The NATO headquarters is located in Brussels, Belgium, while the headquarters of Allied Command Operations is near Mons, Belgium. The organization's motto is "animus in consulendo liber" (Latin for "A mind unfettered in deliberation")