Defense Information Systems Agency

The Defense Information Systems Agency (DISA) is a combat support agency of the United States federal government responsible for planning, developing, fielding, operating, and supporting command, control, communications, and information systems that serve the needs of the President, the Secretary of Defense, the Joint Chiefs of Staff, the Combatant Commanders in Chief (CINCs), and other Department of Defense (DOD) Components under all conditions of peace and war.

Source: http://www.disa.mil/main/missman.html (which as a work created by the United States Government without a copyright notice can be considered to be in the public domain).