North Atlantic Treaty

A treaty signed on April 4, 1949, in Washington, D.C., by twelve independent nations including the United States, Canada, and several western European states. It was entered into force on August 24, 1949. It established an international military security alliance, known as the North Atlantic Treaty Organization, or NATO, to oppose Soviet expansionism in Europe after World War II.

See the Introduction, Abbreviations and Pronunciation for further details.