December of 1965 saw permission granted for MARS stations in Vietnam to begin operations. Just in time for the Christmas season. During the Vietnam War a small number of Marines, all licensed ham radio operators (sometimes known as radio geeks) in civilian life, were given civilian amateur radio equipment and told to use their ham radio skills to run phone patches, or telephone calls home for their fellow Marines. This was extremely important to Marines especially at Christmas time. The operation was called the Military Affiliate Radio System or "MARS". Most of the operators lived in their radio stations, which were known by their call signs. November zero echo foxtrot alpha (N0EFA) was the first operating station. Eventually there were stations Alpha through Zebra (N0EFZ) in Vietnam and on hospital ships off the coast. They had their own chain of command, went by only first names (even on the radio) and answered only to other MARS personnel. Their counterparts in the United States placed collect telephone calls to the families and friends of the Marines in the field and patched the calls through on frequencies near the ham bands. 
 

The United States Marine Corps MARS Operations In Vietnam
Early in the Vietnam war there was no such thing as a MARS operator MOS (Military Occupation Specialty) in the Marine Corps. Operators came from infantry, recon, tanks, artillery, motor transport, engineers, helicopters, air wing and just about every other job in the Marine Corps. A few even came from communications. The one thing they had in common was ham radio. Some had been members of their high school amateur radio clubs just a few short months before and few had the money to invest in a real store-bought radio. Many had built their own or converted old WWII military surplus radios. But the Marine Corps handed them fifty to a hundred thousand dollars worth of state-of-the-art ham radio equipment and said, "Go play".