Forward air controllers (FACs) played a significant part in the Vietnam War from the very start. Largely relegated to airborne duty by the constraints of jungled terrain, FACs began operations as early as 1962. Using makeshift propeller-driven aircraft and inadequate radio nets, they became so essential to air operations that the overall need for FACs would not be completely satisfied until 1969. The FAC's expertise as an air strike controller also made him an intelligence source, munitions expert, communication specialist, and above all, the on-scene commander of the strike forces and the start of any subsequent combat search and rescue if necessary.
Present as advisors under Farm Gate, FACs grew even more important as American troops poured into Vietnam after the Gulf of Tonkin incident. The U.S. Air Force (USAF) would swell its FAC complement to as many as 668 FACs in Vietnam by 1968; there were also FACs from the U.S. Army, U.S. Navy, U.S. Marine Corps, and allied nations. For the early years of the war USAF manning levels were at about 70% of need; they finally reached 100% in December 1969. The FACs would be essential participants in close air support in South Vietnam, interdiction efforts against the Ho Chi Minh Trail, supporting a guerrilla war on the Plain of Jars in Laos, and probing home defenses in North Vietnam.
As the war came to center on the Trail in 1969, the FAC role began to be marginalized. Anti-aircraft (AAA) defenses became steadily more aggressive and threatening along the Trail as the bombing of North Vietnam closed down. The communist enemy moved their supply activities to nighttime, quite literally leaving the FACs in the dark. The American response was twofold. They used fixed-wing gunships with electronic sensors to detect communist trucks, and onboard weaponry to destroy them. They also began putting FACs in jet aircraft and in flareships as a counter to the AAA threat. At about the same time, emplaced ground sensors began to complement and overshadow FAC reconnaissance as an intelligence source. FAC guidance of munitions also began to come into play in 1970.
By the time the Vietnam War ended in 1975, the U.S. and its allies had dropped about six times as many tons of bombs as had been dropped in the entirety of World War II. A considerable proportion of this tonnage had been directed by forward air controllers.
Operating environment
Terrain
The Forward Air Controller (FAC) fulfilled many duties during the Second Indochina War. In addition to the usual close air support strike missions to aid South Vietnamese ground forces in their struggle against insurgents backed by the Democratic Republic of Vietnam, he might direct combat search and rescue operations or air interdiction strikes on the Ho Chi Minh Trail. Other FAC duties included escort of supply truck convoys, or involvement in covert operations. The FAC also advised ground commanders on usage of air power, and trained indigenous personnel in forward air control. Most of all, he flew the core mission of visual reconnaissance, seeking information on the enemy.
The airborne FAC flew the Cessna O-1 Bird Dog or other light aircraft slowly over the rough terrain at low altitude to maintain constant aerial surveillance. By patrolling the same area constantly, the FACs grew very familiar with the terrain, and they learned to detect any changes that could indicate enemy forces hiding below. The rugged jungle terrain of South East Asia easily hid enemy troop movements. However, the FAC looked for tracks on the ground, dust settling in foliage, roiled water in streams—all signs of furtive enemy movement. Both unexpected campfire plumes and rows of fresh vegetables growing near water in "uninhabited" areas were also tip-offs to communist camps. However, decoy camps were not unknown; ofttimes fires were kept underground, with the smoke plumes being redirected through a laterally extended chimney. The communist insurgents were proficient in both camouflage and disguise. Camouflage extended down to individual soldiers using green branches to garnish backpacks. As part of disguise, the insurgents would sometimes dress as civilians, even going so far as to dress as monks or as women carrying small children. Despite these evasions, by 1968 FAC visual recon had largely suppressed daytime communist activities.
Flying low and slow over enemy forces was very dangerous for the FACs; however the enemy usually held his fire to avoid discovery. However, when the enemy opened fire, it might hit him with anything from rifle bullets to 37mm antiaircraft cannon. A low pass for post-strike bomb damage assessment was another hazardous duty.