It emphasised deterrence based on the threat that NATO would respond to any aggression against its member countries by every means at its disposal, specifically including nuclear weapons.

Discussions of possible changes in this strategic approach and the need for other options began later in the 1950s and continued until 1967 when, following intensive debate within the Alliance, "massive retaliation" was replaced by the strategy of "flexible response". This concentrated on giving NATO the advantages of flexibility and of creating uncertainty in the minds of any potential aggressor about NATO's response in the case of a threat to the sovereignty or independence of any single member country. The concept was designed to ensure that aggression of any kind would be perceived as involving unacceptable risks.

The above strategies were enshrined in classified documents, which provided guidance to national governments and points of reference for military planning activities. They were not addressed to the general public. Although the underlying concepts were well known, little public discussion about their details was possible because their effectiveness depended greatly on secrecy. They reflected the realities of the Cold War, the political division of Europe and the confrontational ideological and military situation which characterised East-West relations for many years.

As the Cold War continued, however, the Alliance also sought to minimise the risk of confrontation and to lay the grounds for progress towards a more positive relationship with the Soviet Union and the other members of the Warsaw Pact. The Harmel Report, published in 1967, thus established defence and dialogue, including arms control, as the dual pillars of the Alliance's approach to security.

With the end of the Cold War era, the political situation in Europe and the overall military situation were transformed. A new strategic approach evolved during the two years following the fall of the Berlin Wall in 1989. This was debated and discussed within the Alliance and resulted in the Strategic Concept issued in November 1991.

Bearing little relation to previous strategy documents, NATO's new Strategic Concept placed increased emphasis on cooperation with former adversaries. It maintained the security of its member nations as NATO’s fundamental purpose but combined this with the specific obligation to work towards improved and expanded security for Europe as a whole.