What are the implications of EU enlargement for the European security architecture and what are the implications of stopping it? ESDP is already defined by flexible integration and structured co-operation in several areas. That variable geometry is not only a sensible concept for constructing an effective and capable ESDP within the EU-27: including European Neighboring Policy countries in ESDP activities and missions is also a useful approach. It is thus also suitable for the revival of transatlantic burden sharing within NATO and for an improvement of EU-NATO relations.