The development of defence activities related to the European Union has been rapid since the end of the Cold War. The creation of the European Defence Agency (EDA) in 2004 might contribute to greater coherence in the Union’s defence related activities. This article investigates the development that has enabled the creation of the EDA and what these developments mean to the study of European foreign policy. The authors argue - in opposition to Brian White (2001) - that defence should, by 2005, at least be seen as a fourth sub-system of European foreign policy.