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AGM-87 Focus

In the late 1960s, the Naval Weapons Center (NWC) at China Lake modified the AIM-9 Sidewinder air-to-air infra-red guided missile into the AGM-87 Focus for air-to-ground operations as part of the War Against Trucks on the Ho Chi Minh Trail. Most truck strikes took place at night, when movement on the roads reached its peak.

During the critical years from 1968 through 1972, the Air Force carried out the Commando Hunt series of aerial interdiction campaigns against the Ho Chi Minh Trail in southern Laos, trying, in conjunction with ground actions, to use air power and electronics to impede the movement of men and supplies from North Vietnam to the battlefields of South Vietnam.

Between 1959 and 1975, the Democratic Republic of Vietnam (North Vietnam) used a series of trails running through Vietnam, Cambodia and Laos to transport weapons, supplies and reinforcements to the North Vietnamese Army and other sympathizers within South Vietnam. Originally a network of dirt roads, the Ho Chi Minh trail continually expanded and improved until it had become a vast network which included, by 1974, all-weather surfaced roads, footpaths, and a network of gasoline pipelines, according to the National Security Agencys Center for Cryptologic History. The trail became a significant focal point for American military forces.

In 1965, the U.S. began a series of air raids to interdict the massive amounts of supplies rolling down the trail from North Vietnam. In order to determine the success or failure of their aerial effort, the U.S. used Air Force and Navy reconnaissance aircraft to routinely fly over the primary entry points into Vietnam from southern Laos at Tchepone and the Mu Gia and Ban Karai Passes.

The road networks running north and south were photographed at least once a week. The reconnaissance aircraft focused twice as often on the transit points into Vietnam and Cambodia from Laos. These flights sought to confirm the pilots visual estimate of the damage inflicted by U.S. night raids on North Vietnamese trucks running in near-dark conditions through Laos, down the trail to logistics staging areas and to truck parks serving as rest stops for continuing journeys. This reconnaissance effort sought to define both mission effectiveness and targets for the next days raids.

Air Force and Navy reconnaissance aircraft routinely flew over the primary entry points into Vietnam from southern Laos at Tchepone and the Mu Gia and Ban Karai Passes. The road networks running north and south drew the cameras attention at least once a week. The reconnaissance aircraft focused twice as often on the transit points into Vietnam and Cambodia from Laos. In early daylight, these flights sought to confirm the pilotsvisual estimate of the damage inflicted by night raids on North Vietnamese trucks running in near-dark conditionsthrough Laos, down the trail to logistics staging areas and to truck parks serving as rest stops for continuing journeys.

The Gunship II, the AC130A, was based on the successful Lockheed C130A transport. An infrared detection unit, located in the lower left side of the fuselage, searched ahead for heat from internal combustion engines or campfires or scanned areas on which the searchlight operator had focused the infrared beam. From late September through November 1967, Gunship II went to war, bursting on the scene with deadly effect. In one night over the Ho Chi Minh Trail, it demolished eight trucks in a single convoy, and during its operational test, the new gunship received credit for destroying thirty-eight of the ninety-four trucks detected by its sensors.

The variety of sensors on board the different kinds of gunships might include infrared devices, laser target designators, lowlight-level television with a telescopic lens, and Black Crow detectors, which picked up the electronic emissions from the ignition systems of gasoline-powered vehicles. This array of equipment enabled the gunships to locate and engage targets without the aid of flares or a forward air controller. Even gunships, with their formidable array of sensors, could have difficulty locating a target, for the enemy set fires to blind infrared equipment and a camouflaged truck, blending into the jungle, might escape detection by a night observation device or television camera. The infrared sensor and low-light-level television proved overly sensitive to the flares and incendiary logs dropped by the controllers. The illumination that helped the human eye pick out a truck or gun emplacement utterly blinded these devices.

An unknown number of AIM-9B missiles were converted by General Electric and designated AGM-87A Focus I. The AGM-87A was used in Vietnam during 1969/70 for night attacks against IR emitters, such as truck headlights. It is said that the Focus was quite successful in its specialized role, though it did not merit mention in standard histories of the war. The program was discontinued in favor of other weapons. It must be said that the marginal cost exchange ratio of an expensive missile against a cheap truck was not particularly favorable.

There is some potential for confusion of this program with the totally unrelated AGM-48 Skybolt (GAM-87) Air-Launched Ballistic Missile.



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