Secretary of Defense

Secretary of Defense, government. Appointed by the President of the United States, the Secretary of Defense is the principle advisor to the President on all military and defense matters. He is responsible for the formulation and execution of all defense policy and all policy relevant to the Department of Defense. The Secretary of Defense is a ranking member of the National Security Council, and a member of the President's Cabinet.

The office of Secretary of Defense was created in 1947 during the reorganization of the armed forces under Harry Truman. The Secretary of Defense must be a civilian who has not been in an active component of the United States military in over ten years. He is sixth in presidential line of succession.