The North Atlantic Treaty Organization (NATO) is established by 12 Western nations: the United States, Great Britain, France, Belgium, the Netherlands, Denmark, Italy, Luxembourg, Norway, Iceland, Canada, and Portugal. The military alliance, which provided for a collective self-defense against Soviet aggression, greatly increased American influence in Europe.
Greece, Turkey, and West Germany later joined NATO, but in 1966 France withdrew, citing American violations of the 1949 treaty. In 1955, the Warsaw Pact, a Soviet-led Eastern European alliance, was established to counter NATO. In 1994, three years after the end of the Cold War, NATO engaged in its first military action as part of an international effort to end two years of fighting in Bosnia-Herzegovina. Poland, Hungary, and the Czech Republic, which all left the Warsaw Pact upon its dissolution in 1991, joined NATO in 1999. Today, there are twenty-nine member states in total.