1962: Marine cryptologists in Vietnam.
Excerpt from http://www.1st-radio-company-usmc.org: In January 1962, by order of then Secretary of Defense McNamara, 1st Composite Radio Company deployed a detachment of Marines, identified as Sub Unit #1, to Pleiku, South Vietnam. Pleiku is located in the Central Highlands of South Vietnam (SVN) known militarily as II Corps. Established as a four month rotational (training) effort and being attached to the U.S. Army Security Group’s 3rd Radio Research Unit (3rd RRU) based at Davis Station, Saigon, SVN, the detachment’s mission was to gather information on the movements, disposition and assist in developing the intentions of North Vietnam and Viet Cong military organizations in support of the 3rd RRU and U.S. forces in Vietnam. The unit was billeted at an Army of Vietnam’s base which also housed U.S. Military Army Advisory and Assistance Group.
The third detachment of the Marines sent to Pleiku saw a few members assigned directly to the 3rd RRU, Saigon to perform vital airborne tactical support in locating enemy units in the immediate area. Together, the combined work of this 3rd detachment’s deployment to Vietnam not only lifted the threat of terminating continued deployments in support of the 3rd RRU, it raised production to a level of production that warranted the Secretary of the Army, on May 14, 1963, to award those Marines in support of the 3rd RRU between January and December 1962, the U.S. Army Meritorious Unit Citation. This outstanding support remained vital to U.S. forces efforts through the evacuation of Saigon in 1967.