The Growth of NATO 1949–2023

The North Atlantic Treaty Organization (NATO) came into being in April 1949, when a treaty was signed by ten western European countries from the continent’s western seaboard, from Portugal in the south to Iceland in the north, plus Canada, and, critically, the United States. The Treaty afforded a collective security system with a joint commitment to come to the defence of any member attacked by a ‘Third Party;’ this ‘party’ perceived to be the Soviet Union. Over the next four decades, four more members enrolled: Turkey, Greece, Germany and Spain, and the organization developed an administrative infrastructure headquartered in Brussels. The Soviet Union countered by establishing its own collective defence treaty with its Eastern European client states, the Warsaw Pact (1955), but this dissolved with the collapse of the Soviet Union in 1991, an event which might have undermined NATO’s raison d’etre. Instead, membership would almost double in the next two decades, as Eastern European states freed from Soviet control flocked to join. Most recently, Finland became a member (and Sweden’s membership awaits ratification) in response to Russia’s invasion of Ukraine in 2022.