The Maastricht Treaty of 1992 was the first to contain provisions on the EU's responsibility for all questions relating to its security, including the eventual framing of a common defence policy. The Treaty defined these tasks as part of the Common Foreign and Security Policy. The Treaty envisaged that the EU, having no military capabilities of its own, will request the Western European Union (WEU) to elaborate and implement planned military measures on its behalf.
The 1997 Treaty of Amsterdam incorporated the WEU's "Petersberg tasks" ("humanitarian and rescue tasks, peace-keeping tasks and tasks of combat forces in crisis management, including peacemaking") into the Treaty on the European Union. This laid the treaty basis for the operative development of the ESDP.
In December 1998, at an Anglo-French summit in St Malo, the leaders of the UK and France decided on the need for a "capacity for autonomous action, backed up by credible military forces". The conflicts in Bosnia and Kosovo added impetus to discussions about the need for a European defence force.
At the Cologne Summit on 3 June 1999, European leaders agreed on a common defence strategy. Their stated desire to incorporate the dormant WEU into the EU by the end of the year 2000 was effectively achieved by the Marseilles Declaration of November 2000.
The Treaty of Nice (2000) entered into force on 1 February 2003. It contains amendments which reflect the operative development of the ESDP as an independent EU project.
The 15 Member States of the EU formally decided to create a rapid reaction force (RRF) of 60,000 men at the Nice European Council (December 7-9 2000).
In its final report of 16 December 2002, the Defence Working Group of the European Convention proposed the creation of a European Armaments and Strategic Research Agency that would incorporate closer forms of cooperation which already exist in the armaments field between certain Member States (OCCAR, LoI).
At their mini-summit on 29 April 2003, the leaders of France, Germany, Belgium and Luxembourg attempted to lay the groundwork for an EU military alliance. However, the event was widely seen as divisive and conducive to a two-speed Europe.