European Union enlargement

The European Union (EU) has expanded a number of times throughout its history by way of the accession of new member states to the Union. To join the EU, a state needs to fulfil economic and political conditions called the Copenhagen criteria (after the Copenhagen summit in June 1993), which require a stable democratic government that respects the rule of law, and its corresponding freedoms and institutions. According to the Maastricht Treaty, each current member state and the European Parliament must agree to any enlargement. The process of enlargement is sometimes referred to as European integration. This term is also used to refer to the intensification of co-operation between EU member states as national governments allow for the gradual harmonisation of national laws.

The EU's predecessor, the European Economic Community, was founded with the Inner Six member states in 1958, when the Treaty of Rome came into force. Since then, the EU's membership has grown to twenty-eight, with the latest member state being Croatia, which joined in July 2013. The most recent territorial enlargement of the EU was the incorporation of Mayotte in 2014. The most notable territorial reductions of the EU, and its predecessors, were the exit of Algeria upon independence in 1962 and the exit of Greenland in 1985.

As of 2018, accession negotiations are under way with Serbia (since 2014), Montenegro (since 2012) and Turkey (since 2005). Serbia and Montenegro have been described by President of the European Commission Jean-Claude Juncker and Enlargement commissioner Johannes Hahn as the front-runner candidates, and projected that they would join by 2025, during the next mandate of the European Commission. Negotiations with Turkey have also been ongoing at a slower pace, particularly since the 2016 Turkish coup d'état attempt due to objections from the EU to the Turkish government's response. Additionally, the United Kingdom is negotiating its withdrawal from the EU, following a referendum in which a majority voted in favour of leaving the EU.

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