Markus Kornprobst examines the common assumption that states usually respond to crises individually, rather than together. He develops an innovative approach to analyse how crisis co-management comes to succeed or fail. He argues that actors draw from repertoires of taken-for-granted ideas, forming a set of pre-judgments. These are then revisited in justificatory encounters, making various degrees of co-management possible or impossible. This judging and justifying in turn leaves an impression on repertoires put to use for co-managing the next crisis. The author uses this model to analyse the attempts by France, Germany and the United Kingdom to co-manage the crises in Bosnia, Kosovo, Afghanistan and Iraq. He links individual reasoning and communication, paving the way for further research into crisis co-management, and providing novel insights into European attempts to act in international affairs.