How can peace be brokered between warring sides in conflicts over self-determination and what roles do external third parties play? This book is the first of its kind to thoroughly explore the effectiveness of aid conditionality and other external tools that third parties — from states and regional organizations to NGOs — bring to the table in peace negotiations. Surveying the existing academic debate on incentives and peace conditionality, the author first identifies the gaps between theory and the needs of third party mediators and facilitators. Analysing in depth the negotiation processes in Sri Lanka (Eelam), Indonesia (Aceh), and the Philippines (Mindanao) as case studies, policy tools likely to be most effective are then identified and policy recommendations developed. This book is an invaluable resource for students, scholars, and practitioners alike.