title: NATO
context: The North Atlantic Treaty Organization (NATO /ˈneɪtoʊ/; French: Organisation du Traité de l'Atlantique Nord; OTAN), also called the North Atlantic Alliance, is an intergovernmental military alliance between 29 North American and European countries. The organization implements the North Atlantic Treaty that was signed on 4 April 1949.[3][4] NATO constitutes a system of collective defence whereby its independent member states agree to mutual defence in response to an attack by any external party. NATO’s Headquarters are located in Haren, Brussels, Belgium, while the headquarters of Allied Command Operations is near Mons, Belgium.
question: When was NATO founded?
answers: 4 April 1949