The 26 EU Member States participating in PESCO on the basis of Council decision (CFSP) 2017/2315 of 11 December 2017 are:

Cooperation among EU Member States on defence is not new as such and has been conducted in different formats in the past, including on joint training and exercise or acquisition and development of military equipment. PESCO builds on these positive examples and enhances scope, focus and outcome:

The possibility for Member States to engage – on a voluntary basis – in Permanent Structured Cooperation (PESCO) in the area of security and defence was introduced by article 42(6) of the Lisbon Treaty on European Union (TEU) which provides that “those Member States whose military capabilities fulfil higher criteria and which have made more binding commitments to one another in this area with a view to the most demanding missions shall establish permanent structured cooperation within the Union framework”. Protocol N°10 on PESCO, annexed to the Lisbon Treaty, stipulates that PESCO is open to any Member States which has higher capacities and undertakes to intensively develop defence capacities through the development of national contributions and their participation in multinational forces, in the main European equipment programmes and in the activities of the EDA in the field of defence capabilities development, research, acquisition and armaments.

The European Council on 22/23 June 2017 agreed “on the need to launch an inclusive and ambitious Permanent Structured Cooperation (PESCO)” to strengthen Europe’s security and defence and to help reach the level of ambition of the EU expressed in the EU Global Strategy published in 2016.

On 13 November 2017 ministers from 23 Member States signed a joint notification on PESCO and handed it over to the High Representative and the Council. Two additional Member States joined them on 7 December 2017. The joint notification set out the principles of PESCO, the list of ambitious and more binding common commitments the Member States agreed to undertake as well as proposals on PESCO governance.  Among the PESCO principles agreed by participating Member States is that it should serves as “an ambitious, binding and inclusive European legal framework for investments in the security and defence of the EU’s territory and its citizens”. Participating Member States also “consider an inclusive PESCO as the most important instrument to foster common security and defence in an area where more coherence, continuity, coordination and collaboration are needed”.

On 11 December 2017, Council decision (CFSP) 2017/2315 of 11 December 2017 formally established PESCO with 25 Member States participating. It allows willing and able member states to jointly plan, develop and invest in shared capability projects, and enhance the operational readiness and contribution of their armed forces. The ultimate objective is to optimize the available resources and improve their overall effectiveness, with a view to the most demanding missions and operations and contributing to the fulfilment of the Union level of ambition.

The key difference between PESCO and other forms of cooperation is the legally binding nature of the commitments undertaken by the participating Member States. The decision to participate was made voluntarily by each participating Member State, and decision-making will remain in the hands of the participating Member States in the Council. This is without prejudice to the specific character of the security and defence policy of certain EU Member States.

On 23 May 2023, Council decision (CFSP) 2023/1015 of 23 May 2023 formally confirmed the participation of Denmark in PESCO, determining the list of the participating Member States to 26.