On 4 April 1949, in Washington, Belgium, Canada, Denmark, France, Iceland, Italy, Luxembourg, the Netherlands, Norway, Portugal, the United Kingdom and the United States sign the North Atlantic Treaty. The Treaty enters into force on 24 August 1949.

On 4 April 1949, the Foreign Ministers of Belgium, Canada, Denmark, France, Iceland, Italy, Luxembourg, the Netherlands, Norway, Portugal, the United Kingdom and the United States sign the North Atlantic Treaty in Washington.

On 4 April 1949, in Washington, José Caeiro da Matta, Portuguese Minister for Foreign Affairs, signs the North Atlantic Treaty.

On 24 August 1949, in Washington, the US President, Harry S. Truman, signs the Convention implementing the North Atlantic Treaty. Behind him, from left to right: Sir Frederick Hoyer Millar (United Kingdom), Henrik de Kauffmann (Denmark), W. D. Matthews (Canada), Louis Johnson, (US Defence Secretary), Wilhelm Munthe de Morgenstierne (Norway), Henri Bonnet (France), Pedro Theotonio Pereira (Portugal), Dean Acheson, (US Secretary of State), O. Reuchlin (Netherlands) and Mario Lucielli (Italy).

On 23 November 1951, the Portuguese Minister for Foreign Affairs, Paulo Cunha (left), and the Minister for the Army, General Abranches Pinto, set off for Rome, where the eighth session of the North Atlantic Council is due to be held from 24 to 28 November.

The session of the North Atlantic Council is held in Lisbon from 20 to 25 February 1952. During this session, the Alliance is restructured: NATO becomes a permanent organisation whose seat is established in Paris.

From 20 to 25 February 1952, the flags of the 14 countries attending the session of the North Atlantic Council fly in front of the Higher Technical Institute in Lisbon.

On 4 March 1952, during his address to the Portuguese National Assembly, MP Borges do Canto welcomes the efficient way in which the Portuguese organised the meeting of the North Atlantic Council, held a few days earlier, from 20 to 25 February, in Lisbon.

On 5 March 1953, the United States Ambassador, Cavendish W. Cannon, delivers an address as the 50th US tank is delivered in Lisbon under the Mutual Defense Assistance Program (MDAP) established between the United States Administration and the Portuguese Government.

Map depicting the signing of the North Atlantic Treaty on 4 April 1949 in Washington and NATO's 12 founding member states. The treaty comes into force on 24 August 1949.