At the peak of the Vietnam War the brigade consisted of more than 23,000 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.

By 1972 the 1st Signal Brigade’s strength stood at less than 2,500 men. On 7 November 1972 the brigade headquarters left Vietnam and transferred its colors to Korea. The 39th Signal Battalion, the first Signal unit to arrive in Vietnam, became the last to leave.

At the height of the Vietnam War, the 1st Signal Brigade grew to a strength of almost 23,000 personnel. This level of strength, roughly the size of a division, would make the unit one of, if not the largest, brigade-sized units to ever

The major units of the 39th were the 232nd Signal Company in the Saigon and Mekong Delta areas, the 178th Signal Company in Da Nang and the 362nd Signal Company which operated all of the long-lines tropo scatter systems through out Vietnam from their headquarters in Nha Trang

In April, Phu Lam became part the reorganization to consolidate communications units in Vietnam when the 1st Signal Brigade (USASTRATCOM) was activated. Shortly thereafter, Regional Communications Group became the immediate higher headquarters of Phu Lam.

Constituted on 26 March 1966 and activated six days later on 1 April in Vietnam, the 1st Signal Brigade was given the complicated mission of originating, installing, operating, and maintaining an incredibly complex communications system that fused tactical and strategic communications in Southeast Asia into a single, unified command.

The 1st Signal Brigade was activated on 1 April 1966 in South Vietnam. The brigade's mission 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.

Later, on 26 May 1966, the embryo unit received its ultimate designation, 1st Signal Brigade. Thus a single, unified structure to control and direct US Army communications effort in the Republic of Vietnam was authorized for the second time. Previously, in 1962, all communications responsibility had rested with the 39th Signal Battalion.

The 39th Signal Battalion was the first regular US Army ground unit to enter Vietnam, but from this modest beginning there followed a steady buildup of Signal troops to match the initially slow but later accelerated growth of US Army forces in Vietnam.

James Norris, Kaneohe, HI, says that the 49th Signal Detachment provided Crypto Logistical support for units around Qui Nhon . Attached to the 41st Sig for rations and billets with operational control from the Theater Communications Logistical Support Center Saigon.