National Command Authority. Term used in the United States military to refer to the top-level command structure of the U.S. armed forces; typically refers to the POTUS, the CINCs and their associated commands. In time of crisis, will refer to whichever person or persons at the top of this structure are currently authorized to issue warfighting commands to U.S. forces. For example, if the POTUS is missing following a nuclear attack, the Vice President may become the top of the NCA until the POTUS is back in contact or confirmed dead. Not set in stone, however; the plan may detail that in the event of the POTUS disappearing, a particular military CINC or other commander gain control. SAC maintained an emergency command post called Looking Glass, manned by a general officer at all times also codenamed that, to whom command of the U.S. nuclear forces would devolve under certain conditions; thus, Looking Glass would be part of the NCA.