National Command Authority

Overview
National Command Authority (NCA) is a term used by the U.S. Department of Defense to refer to the ultimate lawful source of military orders. The NCA comprises the President of the United States (as commander-in-chief) and the Secretary of Defense jointly, or by their duly deputized successors, i.e. the Vice-President and the Deputy Secretary of Defense.

"The NCA consists only of the President and the Secretary of Defense or their duly deputized alternates or successors. The chain of command runs from the President to the Secretary of Defense and through the Joint Chiefs of Staff to the Commanders of the Unified and Specified Commands. The channel of communication for execution of the Single Integrated Operational Plan (SIOP) and other time-sensitive operations shall be from the NCA through the Chairman of the Joint Chiefs of Staff, representing the Joint Chiefs of Staff, to the executing commanders."

- ''Section 3.1, Department of Defense Directive Number 5100.30 December 2, 1971