Impartiality is a guiding principle in United Nations peace operations that has helped legitimize multilateral intervention in dozens of armed conflicts around the world. In practice, it has long been associated with passive monitoring of cease-fires and peace agreements. In the twenty-first century, however, its meaning has been stretched to allow for a range of forceful, intrusive, and ideologically prescriptive practices, all in the name of building durable peace. In Intrusive Impartiality, Marion Laurence explains how these new ways of being "impartial" emerge, how they spread within and across missions, and how they become institutionalized across UN peace operations. Laurence argues that new peacekeeping practices are not only products of top-down pressures from member states or instructions from the UN Secretariat; they often emerge from tacit knowledge and unconscious decisions about how to follow orders or comply with social rules. By foregrounding the creativity and agency of the field staff who are responsible for translating mandates into action, Laurence shows that new definitions and practices of impartiality are products of contestation, learning, and the interplay between top-down pressures and bottom-up drivers of change in UN peace operations. Drawing on original data gathered through extensive fieldwork, Laurence uses evidence from UN missions in Sierra Leone, Côte d'Ivoire, the Democratic Republic of the Congo, and from UN headquarters in New York, to provide an innovative framework for studying authority and change in global governance. In doing so, Intrusive Impartiality sheds light on controversial changes in peacekeeping practice and yields valuable insights about the practical and ethical dilemmas that confront UN peacekeepers.