Foreign and security policy cooperation has long been one of the most ambitious goals of those who favor a more united Europe, yet the original mechanism to achieve this goal, European Political Cooperation, was vague in its scope and severely limited in terms of institutional design. By the time of the Treaty on European Union twenty years later, however, the limited “talking shop” of EPC had been formally institutionalized into a legally binding policymaking process capable of producing common positions and joint actions on a wide range of global problems. Today virtually no major foreign policy issue goes unexamined by the EU, and cooperation is under serious consideration in related areas such as security and defense. How can we explain this cooperation, and in what ways did institutionalization affect EU foreign policymaking? The key challenge here is to understand the various processes by which an informal, extra-legal, ad hoc, improvised system gradually fostered the achievement of cooperative outcomes and progressively enhanced its own procedures to improve the prospects for those outcomes.

As much of this activity took place outside the institutions and procedures of the European Community, an explanation of EU foreign policy may benefit from more general explanations of institutional development rather than other theories, such as functionalism, specifically developed to explain European economic integration. This means taking into account the reciprocal links between institutional development and the propensity of states to cooperate to achieve joint gains.