The history of the North Atlantic Treaty Organization (NATO) begins in the immediate aftermath of World War II when British diplomacy set the stage to contain the Soviet Union and to stop the expansion of Soviet power in Europe. The United Kingdom and France signed, in 1947, the Treaty of Dunkirk, a defensive pact, which was expanded in 1948 with the Treaty of Brussels to add the three Benelux countries (Belgium, the Netherlands, and Luxembourg) and committed them to collective defense against an armed attack for fifty years. The British worked with Washington to expand the alliance into NATO in 1949, adding the United States and Canada as well as Italy, Portugal, Norway, Denmark, and Iceland. Greece and Turkey joined in 1952, West Germany joined in 1955, Spain joined in 1982, Czech Republic, Hungary and Poland joined in 1999, Bulgaria, Estonia, Latvia, Lithuania, Romania, Slovakia, and Slovenia joined in 2004, Albania and Croatia joined in 2009, Montenegro joined in 2017, North Macedonia joined in 2020, and Finland joined in 2023.
The structure of NATO evolved throughout the Cold War and its aftermath. An integrated military structure for NATO was first established in 1950 as it became clear that NATO would need to enhance its defences for the longer term against a potential Soviet attack. In April 1951, Allied Command Europe and its headquarters (SHAPE) were established; later, four subordinate headquarters were added in Northern and Central Europe, the Southern Region, and the Mediterranean.
From the 1950s to 2003, the Strategic Commanders were the Supreme Allied Commander Europe (SACEUR) and the Supreme Allied Commander Atlantic (SACLANT).
Background
The Treaty of Brussels was a mutual defense treaty against the Soviet threat at the start of the Cold War. It was signed on 17 March 1948 by Belgium, the Netherlands, Luxembourg, France, and the United Kingdom and was the precursor to NATO. The Soviet threat became immediate with the Berlin Blockade in 1948, leading to the creation of a multinational defense organization, the Western Union Defence Organisation, in September 1948. However, the parties were too weak militarily to counter the Soviet Armed Forces. In addition, the communist 1948 Czechoslovak coup d'état had overthrown a democratic government, and British Foreign Minister Ernest Bevin reiterated that the best way to prevent another Czechoslovakia was to evolve a joint Western military strategy. He got a receptive hearing in the United States, especially with the American anxiety over Italy and the Italian Communist Party.
1949-1991: Cold War
1949-1962: Beginnings
In 1948, European leaders met with US defense, military, and diplomatic officials at the Pentagon, exploring a framework for a new and unprecedented association. The talks resulted in the North Atlantic Treaty, and the United States signed on 4 April 1949. Participants included the five Treaty of Brussels states, as well as the United States, Canada, Portugal, Italy, Norway, Denmark and Iceland. The first NATO Secretary General, Lord Ismay, stated in 1949 that the organization's goal was "to keep the Russians out, the Americans in, and the Germans down". Popular support for the treaty was not unanimous, and some Icelanders participated in a pro-neutrality, anti-membership riot in March 1949. The formation of NATO can be seen as the primary institutional consequence of a school of thought called Atlanticism, which stressed the importance of trans-Atlantic cooperation.
The members agreed that an armed attack against any of them in Europe or North America would be considered an attack against them all. Consequently, they agreed that if an armed attack occurred, each of them, in the exercise of the right of individual or collective self-defense, would assist the member being attacked and take such action as it deemed necessary, including the use of armed force, to restore and maintain the security of the North Atlantic area. The treaty does not require members to respond with military action against an aggressor. Although obliged to respond, they maintain the freedom to choose the method by which they do so. That differs from Article IV of the Treaty of Brussels, which clearly states that the response is military in nature. NATO members are nonetheless assumed to aid the attacked member militarily. The treaty was later clarified to include both the members' territory and their "vessels, forces or aircraft" north of the Tropic of Cancer, including some overseas departments of France.