The United Nations, NATO and the European Union deploy military operations abroad, but they differ in terms of institutional design (e.g. voting procedures, chairmanship, international secretariat). This paper provides three possible explanations. First, the membership of these international organizations varies with the result that power and influence are differently distributed. Second, these international organizations carry out different military functions and their institutional design varies accordingly. Third, historical path dependency from the Cold War period, during which all three organizations had a different role, continues today. In empirical terms, this paper studies the voting procedures, chairmanship and the international secretariats of the UN, NATO and EU. It shows that decisions on institutional design are to a large extent informed by the variation in membership and functions.
