Common Security and Defence Policy in the context of "European External Action Service"

The Western European Union (WEU; French: Union de l'Europe occidentale, UEO; German: Westeuropäische Union, WEU) was the international organisation and military alliance that succeeded the Western Union (WU) after the 1954 amendment of the 1948 Treaty of Brussels. The WEU implemented the Modified Brussels Treaty. During the Cold War, the Western Bloc included the WEU member-states, plus the United States and Canada, as part of the North Atlantic Treaty Organization (NATO).

The Cold War ended c. 1991, and at the turn of the 21st century, WEU tasks and institutions were gradually transferred to the European Union (EU), providing central parts of the EU's new military component, the European Common Security and Defence Policy (CSDP). This process was completed in 2009 when a solidarity clause between the member states of the European Union, which was similar (but not identical) to the WEU's mutual-defence clause, entered into force with the Treaty of Lisbon. The states party to the Modified Treaty of Brussels consequently decided to terminate that treaty on 31 March 2010, with all the WEU's remaining activities to cease within 15 months.On 30 June 2011, the WEU officially ceased to exist; with the European Union taking over its activities.

The Foreign Affairs Council (FAC) is a configuration of the Council of the European Union that convenes once a month. Meetings bring together the foreign ministers of the member states. Ministers responsible for European affairs, defence, development, or trade also participate depending on the items on the agenda. The configuration is unique in that it is chaired by the High Representative of the Union for Foreign Affairs and Security Policy (HR/VP) rather than the member state holding the presidency of the Council of the European Union. One exception is when the FAC meets in the configuration of ministers responsible for trade (FAC/Trade), with the presiding member state's minister chairing the meeting.

At its sessions, the FAC deals with the EU's external action, including Common Foreign and Security Policy (CFSP), Common Security and Defence Policy (CSDP), foreign trade, and development cooperation. In recent years, in cooperation with the European Commission, the FAC has prioritized ensuring coherence in the EU's external action across the range of instruments at the EU's disposal.

The European Union–Ukraine Association Agreement is a European Union Association Agreement between the European Union (EU), the European Atomic Energy Community (Euratom), Ukraine and the EU's 28 member states at the time (which are separate parties in addition to the EU and Euratom). It establishes a political and economic association between the parties. The agreement entered into force on 1 September 2017; previously parts had been provisionally applied. The parties committed to co-operate and converge economic policy, legislation, as well as regulation across a broad range of areas, including equal rights for workers, steps towards visa-free movement of people, the exchange of information and staff in the area of justice, the modernisation of Ukraine's energy infrastructure and access to the European Investment Bank (EIB). The parties committed to regular summit meetings and meetings among ministers, other officials and experts. The agreement furthermore establishes a Deep and Comprehensive Free Trade Area between the parties.

The agreement commits Ukraine to economic, judicial and financial reforms to converge its policies and legislation to those of the European Union. Ukraine commits to gradually conform to EU technical and consumer standards. The EU agrees to provide Ukraine with political and financial support, access to research and knowledge, and preferential access to EU markets. The agreement commits both parties to promote a gradual convergence toward the EU's Common Security and Defence Policy and European Defence Agency policies.

The European Union Rule of Law Mission in Kosovo, known as EULEX Kosovo or simply as EULEX, is the largest civilian mission ever launched under the Common Security and Defence Policy (CSDP) of the European Union. EULEX supports the Kosovan rule of law institutions on their path towards increased effectiveness, sustainability, multi-ethnicity and accountability, free from political interference and in full compliance with international human rights standards and best European practices.

EULEX's current mandate covers the period to 14 June 2027 and is based on Council Decision 2025/1161. Within its mandate, the Mission undertakes monitoring, mentoring, and advising activities and has limited executive functions.

An EU battlegroup (EU BG) is a military unit adhering to the Common Security and Defence Policy (CSDP) of the European Union (EU). Often based on contributions from a coalition of member states, each of the eighteen battlegroups consists of a battalion-sized force reinforced with combat support elements (1,500 troops). Two of the battlegroups were to be capable for operational deployment at any one time. The civil power that oversees these battlegroups is the Council of the European Union.

The battlegroup initiative reached full operational capacity on 1 January 2007, but, as of November 2023, they had yet to see operational service. They were developed from existing ad hoc missions that the European Union (EU) had undertaken. The troops and equipment are drawn from the Member States of the European Union under the direction of a "lead nation". In 2004, United Nations Secretary-General Kofi Annan welcomed the plans and emphasised the value and importance of the battlegroups in helping the UN deal with troublespots.

The European Defence Agency (EDA) is an agency of the European Union (EU) that promotes and facilitates integration between member states within the EU's Common Security and Defence Policy (CSDP). The EDA is headed by the EU High Representative for Foreign Affairs and Security Policy, European Commission’s Vice President (HR/VP), and reports to the Council. The EDA was established on 12 July 2004 and is based in Brussels, Belgium, along with a number of other CSDP bodies.

All EU member states take part in the agency.

The Western Union (WU), also referred to as the Brussels Treaty Organisation (BTO), was the European military alliance established between France, the United Kingdom (UK) and the three Benelux countries (Belgium, the Netherlands, Luxembourg) in September 1948 in order to implement the Treaty of Brussels signed in March the same year. Under this treaty the signatories, referred to as the five powers, agreed to collaborate in the defence field as well as in the political, economic and cultural fields.

During the Korean War (1950–1953), the headquarters, personnel and plans of the WU's defence arm, the Western Union Defence Organisation (WUDO), were transferred to the newly established North Atlantic Treaty Organization (NATO), providing the nucleus of the European half of NATO's command structure (Allied Command Europe), led by Supreme Headquarters Allied Powers Europe (SHAPE). As a consequence of the failure of the European Defence Community in 1954, the London and Paris Conferences led to the Modified Treaty of Brussels (MTB) through which the Western Union was transformed into the Western European Union (WEU) and was joined by Italy and West Germany. As the WEU's functions were transferred to the European Union's (EU) European Security and Defence Policy (ESDP) at the turn of the 21st century, the Western Union is a precursor of both NATO and the military arm of the EU.

The Edinburgh Agreement or Edinburgh Decision is a December 1992 agreement reached at a European Council meeting in Edinburgh, Scotland, that granted Denmark four exceptions to the Maastricht Treaty so that it could be ratified by Denmark. This was necessary because, without all member states of the European Union ratifying it, it could not come into effect. Denmark had first rejected the Maastricht treaty, but with the addition of the Edinburgh Agreement, ratified the treaty in a 1993 referendum. The member states that had already ratified the Maastricht Treaty did not have to do so again.

Denmark obtained four opt-outs from the Maastricht Treaty following the treaty's initial rejection in a 1992 referendum. The opt-outs are outlined in the Edinburgh Agreement and concern the Economic and Monetary Union (EMU), the Common Security and Defence Policy (CSDP), Justice and Home Affairs (JHA) and the citizenship of the European Union. With these opt-outs the Danish people accepted the treaty in a second referendum held in 1993. On 1 June 2022, Denmark abolished its opt-out from the CSDP.