Army - Nato - Preventing War - Cold Svc X 300 HoodieThe North Atlantic Treaty Organization (NATO, neto ; French: Organisation du trait de l'Atlantique nord, OTAN), also called the North Atlantic Alliance, is an intergovernmental military alliance between 30 member states 28 European and two North American. Established in the aftermath of World War II, the organization implements the North Atlantic Treaty, which was signed in Washington, D. C., on 4 April 1949.