The 1st Signal Brigade was activated on 1 April 1966 in the Republic of Vietnam. The brigade's mission in Vietnam was to originate, install, operate, and maintain a complex communication system that fused tactical and strategic communications in Southeast Asia under a single, unified command. The formation of the brigade brought together three signal groups that were already in South Vietnam.

At the peak of the Vietnam War the brigade consisted of more than 21,000 soldiers, in six Signal groups (including the 160th Signal Group), 22 signal battalions and several communications agencies, making the 1st Signal Brigade the largest signal unit in the U.S. Army at the time.[2]