Third Echelon Headquarters was the main base of operations for Third Echelon, a sub-branch within the National Security Agency (NSA), seen or mentioned during pre-mission cutscenes (or cinematics) in every game in the Splinter Cell series, and featured as one of the missions Sam Fisher explores in Splinter Cell: Conviction. The location of Third Echelon's headquarters remained classified for security reasons, but was believed to be located in a remote area somewhere between Washington, D.C. and Fort Meade, Maryland.