The Office of the Secretary of Defense (OSD) is a headquarters-level staff of the Department of Defense of the United States of America. It is the principal civilian staff element of the Secretary of Defense, and it assists the Secretary in carrying out authority, direction and control of the Department of Defense in the exercise of policy development, planning, resource management, fiscal, and program evaluation responsibilities. OSD (along with the Joint Staff) is the Secretary of Defense’s support staff for managing the Department of Defense, and it corresponds to what the Executive Office of the President of the United States is to the President for managing the whole of the Executive branch of the federal government.