Defense for Sustainment Assistant Secretary of Defense for Energy, Installations, and Environment Assistant Secretary of Defense for Nuclear, Chemical & Biological Defense Programs (NCB) Under Secretary of Defense for Intelligence and Security (I&S) Under Secretary of Defense for Personnel and Readiness (P&R) Deputy Under Secretary of Defense for Personnel and Readiness Assistant Secretary of Defense for Health Affairs (HA) Assistant Secretary of Defense for Manpower and Reserve Affairs (M&RA) Assistant Secretary of Defense for Readiness Executive Director, Defense Human Resources Activity (DHRA) Executive Director, Force Resiliency Executive Director, Personnel and Readiness Under Secretary of Defense for Policy (P) Deputy Under Secretary of Defense for Policy Assistant Secretary of Defense for Indo-Pacific Security Affairs (IPSA) Assistant Secretary of Defense for Global Strategic Affairs (GSA) Assistant Secretary of Defense for Homeland Defense and Hemispheric Affairs (HD&HA) Assistant Secretary of Defense for International Security Affairs (ISA) Assistant Secretary of Defense for Special Operations and Low Intensity Conflict (SO&LIC) Assistant Secretary of Defense for Space Policy Assistant Secretary of Defense for Strategy, Plans, and Capabilities Under Secretary of Defense for Research and Engineering Directors Director of Administration and Management (DA&M) Director of Cost Assessment and Program Evaluation (CAPE) Director of Family Policy Director of Force Transformation Director of Net Assessment Director of the Office of Corrosion Policy and Oversight Director, Operational Test and Evaluation (DOT&E) Director of Small Business Programs Former elements Assistant Secretary of Defense for Networks and Information Integration (NII) Defense Prisoner of War/Missing Personnel Office (DPMO) Major reorganizations The composition of OSD is in a state of consistent flux, as Congress and DoD routinely create new offices, redesignate existing ones, and abolish others. Obama administration changes During the Obama administration, Congress has sought to clarify the organization of OSD, and has worked with the department to move toward a standardization of official naming conventions. Many Defense officials, including the Deputy Secretary of Defense (DEPSECDEF), all five Under Secretaries of Defense (USDs), and all Assistant Secretaries of Defense (ASDs), as well as any officials specifically designated in U.S. Code have historically been considered Presidentially-Appointed, Senate-Confirmed (PAS) officials, in that the Senate must provide "advice and consent" for each individual before he or she can operate in an official capacity. In a March 2009 letter, Senator Carl Levin, Chairman of the Senate Armed Service Committee, wrote that the department was apparently exercising the authority to appoint other significant officials—termed Deputy Under Secretaries of