Explaining European Military Engagement in the Fight Against Daesh

Military involvement in the anti-Daesh coalition has been characterized by substantial variance, particularly among European Union (EU) member states. Whereas several countries assumed leading roles in the airstrikes, others limited their contributions to the provision of training for local forces, and still others merely expressed their political support for the aims of the coalition or showed no involvement whatsoever. How to account for these differences? This chapter examines five potential explanations derived from the literature on alliance and coalition warfare. The results provide a differentiated picture, demonstrating that none of these can individually account for the observed variance. However, certain factors show up prominently across many of the countries that were involved militarily in the anti-Daesh coalition and others arguably served as effective constraints against military involvement. Specifically, countries with foreign fighters in Iraq and Syria and those with formal alliance membership were prone to become involved militarily. Conversely, the chapter underscores the policy relevance of institutional constraints such as parliamentary veto rights because most of the parliaments of countries that were involved in the airstrikes of the anti-Daesh coalition hold no formal right of involvement on matters of military deployment policy. This resonates with prior work that has emphasized that parliamentary veto rights can constrain democracies’ war involvement if certain preconditions are met.