The Central Security Service (CSS) is an agency of the United States government. It was established by Presidential Directive in 1972 to promote full partnership between the National Security Agency (NSA) and the Service Cryptologic Elements (SCE) of the United States Armed Forces.
According to the NSA website,
"By combining NSA and CSS, we are able to provide a more unified Department of Defense (DoD) cryptologic effort. The CSS comprises all U.S. military services—Army, Navy, Air Force, and Marines. To further ensure joint operations, the Director of the NSA is also the Chief of the CSS."
Tasking of the CSS
According to James Bamford, NSA/CSS was initially conceived as a separate "fourth service" beside the three U.S. armed services. The latter three resisted this idea, and therefore the CSS was founded as an inter-service organization. The day-to-day work of the CSS is to capture enemy signals (radar, telemetry, radio/satellite communications) using the means of the involved service. For example, the Navy has special submarines for tapping undersea cables; the Air Force operates aircraft with sophisticated antennas and processing gear to listen to enemy radar and radio; and on the ground, the Army operates similar eavesdropping equipment.
Obviously, there is the opportunity for a conflict between the three armed services' interests and the objectives of the CSS.