The paper analyses how the UN Secretariat exercises authority in the field of peace operations, a field presumed to be dominated by member states. While the prerogative to mandate missions rests with the UNSC, the Secretariat is in a position to influence missions' composition, range of activities, and interpretation of the mandate. Furthermore, Secretariat's officials contribute to the debate on the future of peace operations through reports and speeches. The paper strives to go beyond the statement that international bureaucracies posses moral and expert authority by looking at the ways in which this authority is practised. Specifically, it discusses how the UN Secretariat exercises authority across the following four functions: setting missions' operational parameters, policy development, reporting, and moral suasion. The first function is perhaps the most straightforward: the Secretariat prepares documents which define how operations approach their mandate, such as budget proposals, planning directives, and rules of engagement. The development of policy and guidance for various aspects of peace operations is another way in which the Secretariat exercises authority. Reports and studies commissioned or researched by Secretariat's officials enable it to play three distinct roles: an agenda-setting role (by providing a platform for the Secretariat to call attention to thematic or situation-specific issues); a framing role (by allowing it to categorise situations facing the UN and thus create the conditions of possibility for particular types of responses); and an evaluation role (by enabling it not only to assess performance but also set the criteria for such assessment, which may have important consequences in a field of peace operations where "success" and "failure" are elusive). Moral suasion, which is among international bureaucrats' better theorised functions, allows the Secretariat to play the first of the two abovelisted roles as well as attempt to change minds through argumentation.