The Secretary of Defense is the head of the US Department of Defense, and serves as the supervisor of the Joint Chiefs of Staff and the commanders of all ten Unified Combat Commands. The Secretary is the principal military and defense policy advisor to the president and is responsible for formulating a general defense policy in regards to all matters of concern for the US department of Defense as well as overseeing the execution of that policy. But, perhaps the most important duty of the Secretary of Defense is his role in the NCA or National Command Authority, the secretary and US President together comprise this two member board, the NCA has sole authority to launch a nuclear weapon and cannot do so unless both the Secretary of Defense and President of the United States concur that a strike should be carried out. The Secretary of Defense is sixth in the presidential line of succession and is considered one of the big four cabinet positions.
