How can two enemies, locked into a spiral of fear and insecurity, transform their relationship into a trusting one? Trusting Enemies argues that the field of International Relations has not done a good job of answering this question. This is because it has been looking in the wrong place. Where trust-building has been theorized by the discipline of International Relations, the focus has been on the state and the individual. This book argues that there is a need to appreciate the importance of a new level of analysis in trust research—the interpersonal. In its development of a theory of interpersonal trust between state leaders in adversarial relationships, this book argues that the obstacles to leaders sincerely signalling their peaceful intent can be overcome and that trust-based relationships provide the greatest assurance of accurate signal interpretation. This book examines three cases: the interaction between US and Soviet leaders Ronald Reagan and Mikhail Gorbachev and its role in ending the cold war; the interaction between Indian Prime Minister Atal Bihari Vajpayee and Pakistani Prime Minister Nawaz Sharif and its role in the Lahore peace process of 1998–9; and the interactions across 2009–10 between Barack Obama and Ayatollah Ali Khamenei that did not lead to a breakthrough in the US–Iranian nuclear relationship.