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Ho Chi Minh Trail

A faceless enemy moving silently southward under the jungle-covered mountains of eastern Laos, gliding slowly but irresistibly like a giant snake. This deadly, well-camouflaged snake was nearly invisible to Air Force eyes, but it struck back viciously when it sensed danger. Worse yet, like a mythical serpent cut into pieces again and again, it kept bringing itself back together . . . steadily carrying its venom southward towards the South Vietnamese and American forces defending the Republic of Vietnam. The "snake" was the North Vietnamese Army, the likes of which the United States Air Force had never before encountered.

During World War II and the First Indochina War, the Vietminh needed and developed effective "backwoods" logistics systems. Included among these were routes which connected the northern and southern parts of Vietnam. With the beginning of the Second Indochina War, this trail network was deliberately improved and operated to support the aims of North Vietnam. Collectively, this system was known as the Ho Chi Minh Trail.

In the Vietnamese language, its classified title was "Doan 559." The secret wasn't so much the identity of the organization itself - the 559th Transportation Division, Rear Services Directorate, of Hanoi's Ministry of Defense - but rather its mission. Simply maintaining and protecting an obscure road network in a remote region would hardly seem to justify the extraordinary measures the Democratic Republic of Vietnam (DRV) expended to hide the 559th's mission. Unless, of course, this obscure road network was the same highway about to become famous around the world in its English translation nickname, "The Ho Chi Minh Trail."

Group 559 had the mission of creating a transportation network in Laos and was the operator of the Ho Chi Minh Trail. This and subordinate organizations employed approximately 100,000 people at any given time during the war. These personnel included engineers, porters, drivers, mechanics, laborers, ground security units, anti-aircraft units, hospitals, and a complete assortment of other administrative and logistical support units.

The Ho Chi Minh Trail was not so much a single route but a network. In general it started with the transportation arteries in North Vietnam, swung west into Laos, south parallel to the South Vietnamese border, and at various points crossed back to the east and into South Vietnam. Some of the trails also went directly across the DMZ and into South Vietnam. The Laotian part of the system continued further south into Cambodia and intersected with a network there which was known as the Sihanouk Trail. The routes consisted mostly of small trails for personnel movement and roads for vehicles. Personnel generally walked or pushed bikes along narrow foot-paths.

These personnel were both porters carrying war supplies and soldiers going south to fight. This means was used throughout the war and constituted both a major asset for the North Vietnamese and one which was extremely difficult to interdict. The terrain also necessitated a vast amount of bridging to span the numerous rivers, streams, and valleys.

Once the roads were established, beginning in 1965, heavy equipment and supplies were moved mostly by vehicle. Eventually, the engineering effort would make many of the routes all-weather, thus evening out the cyclic nature of infiltration. The individual NVA soldier slogged on foot down the 600-mile-long Ho Chi Minh Trail for two to three months before exiting somewhere in South Vietnam. But supplies were carried in vehicles. As early as 1965, an estimated 51 percent of these supplies went south in trucks on the steadily growing road network. The percentages would grow. The low-tech NVA was proving the worst of all possible targets for a high-tech air force better suited for an opponent in its own league. To incredulous intelligence officers, the snake actually seemed to be growing stronger on the diet of American bombs.

Thousands of laborers worked around the clock to expand the Ho Chi Minh Trail and repair damage caused by US air strikes. Some were North Vietnamese volunteers, many of whom were young women given room and board, clothing, and the equivalent of $1.50 per month; others were prisoners and local Laotians who had been conscripted.

President Lyndon Johnson responded in April 1965 by directing an Air Force/Navy "maximum effort" against the Ho Chi Minh Trail. Increased tactical air strikes were ordered, and for the first time the USAF's giant, eight-engined B-52 strategic bombers joined the stick thrashing the Ho Chi Minh Trail. Results: intelligence figures showed the 1965 NVA infiltration numbers more than doubled over those of 1964. In addition to their legendary endurance, members of the NVA had accomplished this feat through expert use of camouflage, underwater bridges not visible to aerial view, and tactics such as throwing gasoline-soaked rags along roads to seduce strike pilots into believing they had struck meaningful targets.

The United States' aerial effort in the 1970s to interdict the massive amounts of supplies rolling down the Ho Chi Minh Trail from North Vietnam needed regular and reliable evidence of success or failure. Did the mission succeed? That question needed a timely answer, daily.

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 camera's 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 pilots' visual estimate of the damage inflicted by 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 possible targets for the next day's work.

In spite of these assets, in 1970 the needed assessments did not come easily. In one case, the crew of an RF-4C reconnaissance aircraft flying early morning missions during the 1969-1970 dry season could confirm only seven of 103 trucks reported destroyed during the first six weeks after the intense rain ceased. Given the proven effectiveness of the AC-130 gunships and repeated pilot reports of success, the inability to verify the damage inflicted became a critical problem. Did the missions fail? Were the pilots mistaken? Did the North Vietnamese road crews clear the debris away and repair the bomb craters quickly enough to cover up any sign of the attack?

Upon careful consideration, it seemed that the answer rested with the standard charts then in use by planners. In 1970, detailed and accurate charts of Laos proved hard to find. Photointerpreters gradually discovered that the maps and charts of Laos used for the Ho Chi Minh Trail interdiction missions, as well as other efforts, regularly demonstrated errors of a few thousand meters. If the RF-4C reconnaissance and assessment teams had been flying to flawed coordinates to monitor the effect of night missions accomplished just a few hours earlier, that would explain a great deal.

To address this problem, the Air Force introduced the long-range navigation (loran) system into the equation. Loran defines the location of any strike site by determining its distance from a known location via the elapsed time of a dedicated radio signal between two or more points-providing much greater precision. The promise of using loran led the Air Force and the Aeronautical Chart and Information Center (ACIC) in St. Louis, Mo., an NGA predecessor, to take this possible solution a step further. The cartographers at ACIC took high-altitude photographs of Laos, Cambodia and Vietnam and broke them into sections, 10 miles square. Loran-directed RF-4Cs photographed each block, and the cartographers transferred the loran data to a series of photo maps, combining the high altitude work with the need to have accurate maps and charts.

The loran control points on the photomaps then went into a growing database along with other significant mission locations identified by the Air Force using those very same points. By 1971, the database became available for use at the 12th Reconnaissance Intelligence Technical Squadron at Tan Son Nhut airbase near Saigon. With accurate fixed points both on the photomaps and retrievable from the computer, the reconnaissance squadron could within 45 minutes accurately confirm the location of any strike point along the trail with a radio fix that related that location to the nearest known loran control point.

With this available combination of talent and technology, the photointerpreters began working with forward air controllers to address the immediate needs of any mission in progress with the new loran-driven tools. The controllers would have the photomaps in hand, with a special grid superimposed. They provided the location of a target or a successful strike as portrayed on their photomap to the technical squadron at Tan Son Nhut, along with the information supplied by the grid. The technical squadron could then supply the pilot with his loran position, both for his purpose and to revisit the point of attack later for evaluation and lessons learned.

Following the January 1973 Paris cease-fire agreement, PAVN had greatly expanded its logistics lifeline to the South, the Ho Chi Minh Trail. With the trail complex no longer subject to US air attacks, North Vietnam was shipping massive quantities of supplies and equipment southward--80,000 tons of military supplies in 1973 alone, including 27,000 tons of weapons, 6,000 tons of petroleum products, and 40,000 tons of rice. One hundred thousand fresh PAVN troops had marched down the trail to the South during 1973, and another 80,000 were on their way south during the first half of 1974. PAVN's troop strength in the South, decimated by the 1972 Easter offensive, now stood at its highest level of the war--400,000 full-time soldiers.

By 1975,the NVA had matured into a modern mechanized force; to exploit this new capability, they upgraded the Ho Chi Minh Trail into a two-lane highway, paralleled by a pipeline with pumping stations for supplying fuel. This "trail" was supplemented by a network of east-west feeder roads, particularly in the I Corps area, that allowed the North Vietnamese to launch their attacks eastward with great rapidity from sanctuary positions close to the South Vietnamese positions. By attacking on a basically west-to-east axis, the NVA prevented the ARVN divisions in I and II Corps from concentrating their forces as they could have done if the NVA had been forced to launch their assault across the DMZ along a generally north-to-south axis.

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Page last modified: 14-03-2012 14:26:33 ZULU