The Evolving Concept for Communications As Conceived in 1966 At
the beginning of 1966, there were two Army divisions and three
separate infantry brigades in South Vietnam as well as a larger
number of combat support and combat service support units.
Headquarters, I Field Force, Vietnam, under the command of Major
General Stanley R. Larsen, controlled the U.S. Army combat units
deployed in II Corps Tactical Zone. The 1st Infantry Division
controlled those in the III Corps Tactical Zone. At that time
except for signal and aviation units, there were no U.S. Army
combat units in the I and IV Corps Tactical Zones, although the
1st and 3d Marine Amphibious Divisions were in the I Corps
Tactical Zone. The major U.S. Army units in Vietnam by January
1966 were the 1st Infantry Division with its 121st Signal
Battalion, the 1st Cavalry Division with its 13th Signal
Battalion, and the 173d Airborne Brigade. U.S. Army strength in
Vietnam was to more than double in the course of 1966,
increasing from approximately 117,000