Trusteeship and the civilizing mission in international relations did not end with the emergence of the self-determination entitlement that led to decolonization in the second half of the 20th century. International organizations, whose modern form emerged during the height of colonialism, took on the 'civilizing' role in the 'post-colonial' era, internationalizing trusteeship and re-legitimizing it as a feature of international public policy into the bargain. Through analysis of the history of and purposes associated with the involvement of international organizations in territorial administration, such as the UN missions in Kosovo and East Timor, a comparison between this activity and colonial trusteeship, the Mandate and Trusteeship arrangements, and an exploration of the modern ideas of international law and public policy that underpin and legitimize contemporary interventions, this book relates a new history of the concept of international trusteeship. From British colonialist Lord Lugard's 'dual mandate' to the 'state-building' agenda of the High Representative in Bosnia and Herzegovina, Lord Ashdown, wide-ranging links between the complex peace operations of today and the civilizing mission of the colonial era are established, offering a historical, political, and legal framework within which the legitimacy of, and challenges faced by, complex interventions can be appraised. This new history of international trusteeship raises important questions about the role of international law and organizations in facilitating relations of dominations and tutelage, and suggests that the contemporary significance of the self-determination entitlement needs to be re-evaluated.