In 2009, the Lisbon Treaty introduced major institutional innovations in the field of the Common Foreign and Security Policy (CFSP), including a High Representative with three hats, a European External Action Service (EEAS), a permanent chair of the European Council and - for the first time in EU integration - a form of carefully formulated flexible integration in military matters, namely the Permanent Structured Cooperation. Yet, compared to other policy fields equally characterized by severe concerns regarding the safeguarding of national sovereignty rights (Economic and Monetary Union (EMU);Area for Freedom, Security and Justice (AFSJ), the CFSP is much less integrated and the institutional and procedural opportunities as designed by the Lisbon Treaty are only used to a limited extent. Put in a long-term perspective, this article argues that these differences can only be explained when taking into account not only the level of supranationalization (internal factor), but also the structure of the international system and the interests of major powers (external factor). We explore the working thesis that the limited problem-solving pressure and the persisting European reliance on the United States in foreign and security matters has slowed down integration efforts in the field of CFSP. Given the weak performance of the CFSP post-Lisbon in the context of an emerging multipolar world order, we identify only incremental deepening and an inclination towards low level activities. However, the fuller use of the legal innovations of the CFSP might be triggered in the future by systemic shifts such as an accelerated shift of the strategic focus of the US away from Europe and towards Asia. In turn, future external shocks would increase the pressure on EU states to cooperate and to pool their foreign policy resources in the Union's framework more effectively.