Defence cooperation between European Union member states has long
been characterised by a high level of fragmentation. To manage, and
potentially overcome, some of the existing divides, differentiation has
been recognised as one way forward, exemplified by the activation of
Permanent Structured Cooperation (PESCO) and discussions about
the use of Article 44 of the Treaty on European Union. However, beyond
treaty-based forms of differentiation, EU member states have also
joined extra-EU frameworks for defence cooperation such as the Joint
Expeditionary Force, the Framework Nations Concept and the European
Intervention Initiative, which embody different levels of formalisation,
diverse memberships and foci, as well as varying links to the EU and
NATO. This Policy Brief analyses whether this kind of differentiated
cooperation outside the EU structures contributes to the long-term
prospects of European integration in security and defence, or whether it
adds to the existing fragmentation within the EU and European defence
more broadly. The paper argues that the flexible defence frameworks
bear some potential for enhancing defence cooperation among EU
member states, but also present challenges. Moreover, their ability to
manage diversity in European defence remains largely unproven.