In coercive diplomacy, states threaten the use of force to get opponents to change their behaviour without incurring the cost in blood and treasure of military intervention. Coercers typically employ this strategy toward weaker actors, but targets often refuse to submit and the parties enter into war. Why do states reject coercive threats from more powerful opponents? This book argues that target leaders' decision-making can be shaped by their emotions in significant ways. It introduces a logic of affect that focuses on the dynamic interplay between target leaders' norms, identities, and five key emotions, namely fear, anger, hope, pride, and humiliation. The study applies the logic of affect to Nikita Khrushchev's decision-making during the Cuban missile crisis in 1962 and Saddam Hussein's choice behaviour in the Gulf conflict in 1990-91, offering a novel explanation for why coercive diplomacy succeeded in one case but not in the other.