After the failure of the European Defence Community (EDC), following France's rejection in 1954, foreign policy was clearly absent from Europe's first years and particularly from the Treaty of Rome (1957). It only made a modest return to the agenda in June 1970. The foreign affairs ministers from the six member states proposed developing European Political Cooperation (EPC). This cooperation progressed slowly: an increase in meetings, the special European correspondence system (COREU). But it remained very informal. It was not until the Single Act, in 1986, and the Maastricht Treaty, in 1992, that a solid legal and institutional basis was established.

This was not sufficient, as demonstrated by the conflicts in Yugoslavia in the first half of the 1990s. The failure of the Europeans was evident (in Croatia and Bosnia, in particular). It was to serve as a spur for all future reforms. In the midst of conflict, ministers from the Western European Union (WEU) thus defined the outlines of a 'Europe of defence'. These were the 'Petersberg tasks', ratified in the Amsterdam Treaty (1997). This treaty created the post of high representative to coordinate the Common Foreign and Security Policy (CFSP). Since 1999, this position has been held by the former NATO Secretary-General, Javier Solana (Spain).

It was a Franco-British initiative, in Saint Malo (December 1998), which really launched the 'Europe of defence', by calling for the Union to be equipped with "an autonomous capacity for action, relying on credible military forces, with the resources to use them". These objectives were taken up by the 15 heads of state and government at the Cologne European Council (June 1999). They ratified, in Helsinki (December 1999), the format for a European Rapid Reaction Force (ERRF), "capable of deploying up to 60,000 men in 60 days".

The Nice Treaty (2000) added decision making structures, such as the Political and Security Committee (PSC) – composed of the EU's 'security' ambassadors - and the EU Military Committee – composed of military staff or their representatives. The European Defence Policy was declared operational at the Laeken-Brussels Summit (2001). A European security strategy was defined (2003) in the context of European divisions following America's intervention in Iraq. An agreement (known as 'Berlin Plus') was made with NATO to resort to its means at the time of a military operation (March 2003), and the first external operations were deployed (Macedonia, Bosnia, Indonesia, Congo).

The European Defence Agency was created, in July 2004, with the mission of developing industrial cooperation and strengthening the capacities of the various member states. The European Union Military Staff (EUMS) was set up, and was equipped with an Operations Centre, in 2007. A crisis management capability, and the Civilian Planning and Conduct Capability (CPCC), saw the light of day in 2008.