The Balkan countries have responded differently to the EU's conditional offer of membership. This book examines the diverging compliance patterns of the Balkan accession states and asks why some of them have complied substantially, some only partially and others have defied the EU. The book examines the compliance of the Balkan states with the EU accession conditionality, arguing that the variation in the compliance behavior of Balkan governments hinges on three main factors - the legitimacy of the EU conditions as seen domestically in the accession states, the costs of compliance and the EU's ability and willingness to use its superior power resources to impose compliance when faced with domestic defiance. Placing important events from the most recent political history of the Balkans in a broader historical perspective, the author evaluates the successes and failures of the EU's state building policies in the Balkans, a geographical area of the highest priority for the EU's foreign policy and a test case for the EU's capacity and willingness for foreign policy action. Based on detailed empirical data, European Foreign Policy and the Challenges of Balkan Accession will be of interest to scholars and students of EU and comparative politics, and those focusing on policy impact in EU integration.