The U.S. Secretary of Defense (SECDEF) is
the principal defense policy adviser to the President and is responsible for the formulation of general defense policy and policy related to all matters of direct concern to the Department of Defense, and for the execution of approved policy. Under the direction of the President, the Secretary exercises authority, direction and control over the Department of Defense. The Secretary of Defense is a member of the President's Cabinet and of the National Security Council.
The Secretary is appointed by the President with the approval of the Senate. By statute the Secretary must be a civilian who has not served in the active component of the armed forces for at least ten years.