The National Security Council is chaired by the President, Barak Obama. The next in line is the Vice President, Secretary of State, the Secretary of Treasury, and then the Secretary of Defense. For more information on the layout of the National Security Council, please visit the following link: http://www.whitehouse.gov/administration/eop/nsc/
The Principal military adviser to the National Security Council is The Chairman of the Joint Chiefs Staff. Joint Chiefs Staff is a body of senior uniformed leaders in the United States Department of Defense who advise the Secretary of Defense.
The Joint Chiefs of Staff is the military adviser to the National Security Council. The current chairman of the Joint Chiefs of Staff is General Martin E. Dempsey. For more information, please see this link: http://www.jcs.mil/biography.aspx?ID=135