'Using European security initiatives as a test case, Stephanie C. Hofmann shows that the convergence of party ideologies across countries creates opportunities for international cooperation. Sharply argued, carefully researched and well written, this book makes the exciting argument that party ideologies matter in international relations. Hofmann also shows that it is impossible to understand European security initiatives such as CFSP and ESDP without taking into account the presence of an alternative, namely NATO, which makes the creation of a new European institution costly and perhaps superfluous unless one factors ideological preferences in.' Frédéric Mérand, University of Montréal