The European Union (EU) plays a fundamental role in Europe's security. The EU's capabilities are undergoing significant changes, which are increasingly reflected in the conceptual design of its Neighbourhood Policy (ENP). These changes result both from the external context within which EU policies are implemented and from the institutional and political context in which they are designed. Regarding the former, we identify several turning points which have affected European security since the inception of the ENP, in 2003. These include developments in EU-US relations, the North Atlantic Treaty Organisation (NATO) and EU enlargements in a post-9/11 context, the important role of Russia and its relations with former-Soviet countries, as well as the Arab Spring events and the political instability in the Southern neighbourhood of the EU. Regarding EU institutional and political context, we focus on the impacts of the 2004/2007 EU enlargements, particularly in terms of the regional agenda that was uploaded onto the EU's regional security con-