Peace operations are the main instrument of the United Nations (UN) to maintain international peace and security. This special issue analyzes how recent changes in world politics, in terms of increased geopolitical competition and contestation of the liberal international order, have influenced UN peace operations. It combines International Relations (IR) theory and peace research by calling for a macro-level analysis of UN peace operations. It thereby contributes to core debates in IR about the changing global order and its manifestations, as well as to peace research by analyzing how structural factors influence the UN’s role in promoting peace. Overall, the special issue further promotes a macro turn in peace research, which we argue is urgently needed at a time when the UN’s role in maintaining international peace and security is questioned by major and emerging powers and by host states.