This policy specifies the authority, command and control (AC2) arrangements for United Nations peacekeeping missions.This policy applies to all personnel involved in the planning of United Nations peacekeeping missions and in the implementation of their mandates. This policy defines and describes the AC2 arrangements at the Headquarters and mission levels; the responsibilities of the Head of Mission (HOM) and other senior mission leadership and mission integration and control arrangements. The policy also specifies the responsibilities retained by Member States over their military and police contingents and units serving in United Nations peacekeeping missions. On the security management issues concerning the protection of United Nations personnel as defined by the United Nations Security Management System, please refer to the United Nations system-wide policy guidance of the United Nations Security Management System (UNSMS), in particular the Framework for Accountability of the UNSMS (Security Policy Manual Chapter II, Section A) and the Applicability of the UNSMS (Security Policy Manual Chapter III, Section A). Individuals accountable under AC2 have roles and responsibilities under the UNSMS as outlined in the Framework of Accountability of the UNSMS.