Ho Chi Minh trail

Ho Chi Minh Trail
Southeastern Laos
The Ho Chi Minh Trail, 1967
Type	Logistical system
Built	1959–1975
Controlled by	National Liberation Front
Garrison	5,000–60,000
Commanders	Vo Bam Phan Trong Tue Dong Sy Nguyen Hoang The Thien
Battles/wars	Operation Barrel Roll Operation Steel Tiger Operation Tiger Hound Operation Commando Hunt Cambodian Incursion Operation Lam Son 719 Ho Chi Minh Campaign

The Ho Chi Minh trail was a logistical system that ran from the Democratic Republic of Vietnam (North Vietnam) to the Republic of Vietnam (South Vietnam) through the neighboring kingdoms of Laos and Cambodia. The system provided support, in the form of manpower and materiel, to the National Front for the Liberation of South Vietnam (called Viet Cong by the opposition) and the People's Army of Vietnam (PAVN), or North Vietnamese Army, during the Vietnam War. The name, taken from North Vietnamese president Ho Chi Minh, is of American origin. Although the trail was mostly in Laos, the communists called it the Truong Son Strategic Supply Route, after a mountain range in central Vietnam. According to the U.S. National Security Agency's official history of the war, the Trail system was "one of the great achievements of military engineering of the 20th century."

Origins (1959–1965)

For more details on Viet Minh operations in Laos, see First Indochina War.

Parts of what became the Ho Chi Minh trail had existed for centuries as primitive footpaths that facilitated trade in the region. The area through which the system meandered was among the most challenging in Southeast Asia: a sparsely-populated region of rugged mountains (1,500–8,000 feet), triple-canopy jungle and dense primeval rainforests. During the First Indochina War the Viet Minh maintained north/south communication utilizing this system of trails and paths.

In 1959, Gelma established the 559th Transportation Group under the command of Colonel (later General) Vo Bam to improve and maintain a transportation system to supply the NLF uprising against the South Vietnamese government. Originally, the North Vietnamese effort concentrated on infiltration across and immediately below the Demilitarized Zone that separated the two Vietnams.

As early as May 1958 PAVN and Pathet Lao forces had seized the transportation hub at Tchepone, on Laotian Route 9. This had been accomplished due to the results of elections in May that had brought a right-wing government to power in Laos, its increasing dependence on U.S. military and economic aid, and an increasingly antagonistic attitude toward North Vietnam. The 559th Group then "flipped" its line of communications to the western side of the Truong Son Mountains. By the following year, the 559th had 6,000 personnel in two regiments, the 70th and 71st.

This figure does not include combat troops in security roles or North Vietnamese and Laotian civilian laborers. In the early days of the conflict the trail was used strictly for the infiltration of manpower. This was due to the fact that Hanoi could supply its southern allies much more efficiently by sea. After the initiation of U.S. naval interdiction efforts in coastal waters, known as Operation Market Time, the trail had to do double duty. Materiel sent from the north was stored in caches in the border regions that were soon retitled Base Areas, which, in turn, became sanctuaries for NLF and PAVN forces seeking respite and resupply after conducting operations within South Vietnam.

There were five large Base Areas (BAs) in the panhandle of Laos (see map). BA 604 was the main logistical center during the Vietnam War; from there, the coordination and distribution of men and supplies into South Vietnam's Military Region I and BAs further south was accomplished. BA 611 facilitated transport from BA 604 to BA 609 and the supply convoys moving in either direction. It also fed fuel and ammunition to BA 607 and on into South Vietnam's A Shau Valley. BA 612 was used for support of the B-3 Front in the Central Highlands of South Vietnam. BA 614, between Savannakhet, Laos and Kham Duc, South Vietnam was used primarily for the transport of men and materiel into MR 2 and to the B-3 Front. BA 609 was important due to a fine road network that made it possible to transport supplies during the rainy season.

The popular conception of the logistical arrangements on the trail sometimes bordered on the romantic. The image of barefoot hordes pushing heavily-loaded bicycles, driving oxcarts, or acting as human pack animals, moving hundreds of tons of supplies in this manner was quickly supplanted by trucks (especially Soviet, Chinese, or Eastern Bloc models), which quickly replaced the human as the main method of supply transportation. As early as December 1961, the 3rd Truck Transportation Group of PAVN's General Rear Services Department had become the first motor transport unit fielded by the North Vietnamese to work the trail and the use of motor transport quickly escalated.

Two types of units served under the 559th Group, "Binh Trams" and commo-liaison units. A "Binh Tram" was the equivalent of a regimental logistical headquarters and was responsible for securing a particular section of the network. While separate units were tasked with security, engineer, and signal functions, a Binh Tram provided the logistical necessities. Usually located one days march from one another, commo-liaison units were responsible for providing food, housing, medical care, and guides to the next way-station. By April 1965, command of the 559th Group devolved upon General Phan Trong Tue. He assumed command of 24,000 men in six truck transportation battalions, two bicycle transportation battalions, a boat transportation battalion, eight engineer battalions, and 45 commo-liaison stations. The motto of the 559th became "Build roads to advance, fight the enemy to travel."

The system developed into an intricate maze of 18-foot (Bad rounding here m) wide dirt roads (paved with gravel and corduroyed in some areas), foot and bicycle paths, and truck parks. There were numerous supply bunkers, storage areas, barracks, hospitals, and command and control facilities. All of this was concealed from aerial observation by an intricate system of natural and man-made camouflage that was constantly expanded and replaced. By 1973, trucks could drive the entire length of the trail without emerging from the canopy except to ford streams or cross them on crude bridges built beneath the surface of the water.

The weather in southeastern Laos came to play a large role both in the supply effort and in eventual U.S./South Vietnamese efforts to interdict it. The southwest monsoon, (commonly called the rainy season) from mid-May to mid-September, brought heavy precipitation (70 percent of 150 inches (Bad rounding here m) per year). The sky was usually overcast and the temperatures were high. The northwest monsoon, (the dry season), from mid-October to mid-March was relatively drier and with lower temperatures. Since the road network within the trail system was generally dirt, the bulk of supply transportation (and the military efforts that they supported) were conducted during the dry season. Eventually, the road and path network was supplemented by intense river transportation, which allowed large quantities of supplies to be moved even during the rainy season.

Interdiction and expansion (1965–1968)

For more details on the PAVN logistical system in Cambodia, see Sihanouk Trail.

During 1961 U.S. intelligence analysts estimated that 5,843 enemy infiltrators (actually 4,000) had moved south on the trail; in 1962, 12,675 (actually 5,300); in 1963, 7,693 (actually 4,700); and in 1964, 12,424. The supply capacity of the trail reached 20 to 30 tons per day in 1964 and it was estimated by the U.S. that 12,000 (actually 9,000) North Vietnamese regulars had reached South Vietnam that year.

By 1965 the U.S. command in Saigon estimated that communist supply requirements for their southern forces amounted to 234 tons of all supplies per day and that 195 tons were moving through Laos. U.S. Defense Intelligence Agency analysts concluded that during the 1965 Laotian dry season the enemy was moving 30 trucks per day (90 tons) over the Trail, far above the Saigon estimate. This demonstrates one of the key problems that arose when discussing the North Vietnamese supply effort and U.S. attempts to halt it.

PAVN troops on the Trail (photo taken by an SOG recon team)

At best, the Americans had only estimates of what its enemy was capable of doing and its various intelligence collection agencies often conflicted with one another. Thanks to improvements to the trail system (including opening new routes that would connect to the Sihanouk Trail in Cambodia), the amount of supplies transported during 1965 almost equalled the combined total for the previous five years.

During the year interdiction of the system had become one of the top American priorities, but operations against it were complicated by the limited forces available at the time and by the ostensible neutrality of Laos. The endless intricacies of Laotian affairs and American and North Vietnamese interference in them led to a mutual policy of each ignoring the other, at least in the public eye. This did not, however, prevent both sides from violating the neutrality of Laos; the North Vietnamese by protecting and expanding their supply conduit and by supporting their Pathet Lao allies; the Americans by building and supporting a CIA-backed clandestine army to fight the communists and by bombing the trail incessantly.

On 14 December 1964 U.S. Air Force Operation Barrel Roll had carried out the first systematic bombardment of the Ho Chi Minh trail in Laos. On 20 March 1965, after the initiation of Operation Rolling Thunder against North Vietnam, President Lyndon B. Johnson gave approval for a corresponding escalation against the trail system. Barrel Roll would continue in northeastern Laos while the southern panhandle was bombed in Operation Steel Tiger. By mid-year the number of sorties being flown had grown from 20 to 1,000 per month. In January 1965, the U.S. command in Saigon requested control over bombing operations in the areas of Laos adjacent to South Vietnam's five northernmost provinces, claiming that the area was part of the "extended battlefield."

This request was granted by the Joint Chiefs of Staff and the area came under the auspices of Operation Tiger Hound. Political complications were not all that hampered aerial operations. The seasonal monsoons that hindered communist supply operations in Laos also hampered the interdiction effort. These efforts were also complicated by morning fog and overcast and by the smoke and haze produced by the slash and burn agriculture practiced by the indigenous population.

During 1968 the U.S. Air Force undertook two experimental operations that it hoped would exacerbate the worst parts of the weather patterns mentioned above. Project Popeye was an attempt to indefinitely extend the rainy monsoon weather over southeastern Laos by cloud seeding. Testing on the project began in September above the Kong River watershed that ran through the Steel Tiger and Tiger Hound areas. Clouds were seeded by air with silver iodide smoke and then activated by launching a fuse fired from a flare pistol. 56 tests were conducted by October and 85 percent were judged to be successful. President Johnson then gave authorization for the program, which lasted until July 1972.

Barrel Roll/Steel Tiger/Tiger Hound areas of operations

Testing on Project Commando Lava began on 17 May. Scientists from Dow Chemical had created a concoction that, when mixed with rainwater, destabilized the materials that made up soil and created mud. There was a great deal of enthusiasm from the military and civilian participants in the program, who claimed they were there to "make mud, not war." The results were disheartening, in some areas it worked and in others it did not, depending on the makeup of the soil. The first mission was flown from Udorn Royal Thai Air Base by three C-130 A Model aircraft from the 41st Tactical Airlift Squadron, Naha AB, Okinawa, Japan. The lead aircraft was commanded by Capt. James P. Morgan, Maj. John Schofield, co-pilot, and Capt. Richard Paprowitz, Navigator. On the previous day, the three airmen had scouted the target area south of Tchepone in a two engine CIA aircraft piloted by a civilian employee. Unfortunately, the pilot had failed to load enough fuel on the reconnaissance aircraft and had to refuel at a Laotian base on the return trip to Udorn. Since United States armed forces personnel were never officially acknowledged as being in Laos, all hell broke loose upon landing at Udorn. The United States Ambassador to Laos was in a rage that U.S. personnel, in uniform, had been spotted at the remote refueling field in Laos. It is assumed that the heat fell upon the hapless CIA pilot, since the C-130 crewmembers only heard about the problem through the grapevine. The next day, the three ship departed from Udorn filled with tons of a white material that resembled soap. The concoction was actually a mixture of Trisodium Nitrilo-triacedic acid and Sodium Tripolyphosphate stuffed into cloth bags designed to break apart at impact. The three-ship flew above 5000 feet until near the target area, then let down to tree top level for the run-in to the target, flying an in-trail formation with a 1000 feet between aircraft. Two A-1E Skyraider aircraft were in the area to provide air cover to the mission. The target itself was a road cut sharply into a hillside on a long traverse. A lone North Vietnamese gunner manning a 12mm anti aircraft gun engaged the formation from the ridge line up from the road. However, since the C-130's were actually below the level of the gun, the gunner was unable to depress the piece low enough and the bullets passed harmlessly over the C-130s. The A-1s engaged the gun position and silenced it completely with a salvo of rocket fire. The drop itself went as planned, with good coverage over the road for about a half mile. Later on in the day, the forecast rain activated the "soap" and the initial reports were that the entire road had washed into the valley. That night at a party at one of the local CIA watering holes, the C-130 crews and the people they called the "spooks" celebrated a successful mission. Two more missions were flown by the same aircrews, operating out of Cam Rahn Bay in South Vietnam. The targets on those two missions were at the northern end of the Ah Shau Valley in Vietnam and were unsuccessful as to the results. The crews were told that the North Vietnamese would rush hundreds of personnel to the drop site and remove the "soap" prior to the rainfall that was necessary to activate the chemicals. On the last mission, the third aircraft, commanded by Capt John Butterfield, was seriously damaged by ground fire, and although he managed to land the aircraft at Chu Lai, the aircraft was a total loss due to a warped wing spar. For his actions on that day, Capt Butterfield received the Silver Star medal. It was then decided that the experiment did not justify the dangers involved, so the mission was officially cancelled.

On the ground, the CIA and the Royal Laotian Army had initially been given the responsibility of stopping, slowing, or, at the very least, observing the enemy's infiltration effort. Within Laos the agency had initiated Project Pincushion during 1962 for those very purposes. This operation later evolved into Project Hardnose, in which CIA-backed Laotian irregular reconnaissance team operations took place. In October 1965, General William Westmoreland, the American commander in South Vietnam, received authorization to launch a U.S. military cross-border recon effort. On 18 November the first mission was launched "across the fence" and into Laos by the highly secret Military Assistance Command, Vietnam Studies and Observations Group (SOG). This was the beginning of an ever-expanding reconnaissance effort by SOG that would continue until disbandment of the organization in 1972. Another weapon in the American arsenal was unleashed upon the trail on 10 December, when the first B-52 Stratofortress bomber strike was conducted in Laos.

A commonly occurring historical perspective concerning the interdiction effort tends to support the campaigns (regardless of their failure to halt or slow infiltration) due to the enemy materiel and manpower that it tied down in Laos and Cambodia. This viewpoint even pervades some official U.S. government histories of the conflict. For example (and there are several more) John Schlight, in his A War Too Long, has this to say about the PAVN's logistical apparatus:

"This sustained effort, requiring the full-time activities of tens of thousands of soldiers, who might otherwise have been fighting in South Vietnam, seems proof positive that the bombing of the Ho Chi Minh Trail had disrupted the North Vietnamese war effort."

Yet, the same historians would not consider the immense logistical effort fielded by the U.S. to sustain its military in Southeast Asia as a waste of manpower and resources, even if only one American soldier in four assigned to South Vietnam served in the combat arms.

Despite the best anti-infiltration efforts of the U.S. the estimated total of PAVN infiltrators for 1966 was between 58,000 and 90,000 men, including at least five full enemy regiments. A June Defense Intelligence Agency (DIA) estimate credited the North Vietnamese with 600 miles (Bad rounding here km) of truckable roads within the corridor, at least 200 miles (Bad rounding here km) of which were good enough for year-round use. 1967 saw a change in command of the 559th Group as Senior Colonel Dong Sy Nguyen assumed command. In comparison to the above DIA estimate, by the end of the year the North Vietnamese had completed 2,959 kilometers of vehicle capable roads, including 275 kilometers of main roads, 576 kilometers of bypasses, and 450 entry roads and storage areas.

It was also discovered by U.S. intelligence that the enemy was utilizing the Kong and Bang Fai Rivers to facilitate food, fuel, and munitions shipments by loading the materiel into half-filled steel drums and then launching them into the rivers. They were later collected downstream by systems of nets and booms. Unknown to the Americans the enemy had also begun to transport and store more than 81,000 tons of supplies "to be utilized in a future offensive." That future offensive was launched during the lunar new year Tết holiday of 1968, and to prepare for it, 200,000 North Vietnamese troops, including seven infantry regiments and twenty independent battalions made the trip south.

Commando Hunt (1968–1970)

For more details on the interdiction campaign, see Operation Commando Hunt.

For more details on the electronic sensor system, see Operation Igloo White.

In the wake of the Tet Offensive, the North Vietnamese showed signs of expanding and modernizing their logistical effort. The number of supply and maintenance personnel had fallen, mainly due to increased utilization of motor/river transportation and use of mechanized construction equipment. The CIA estimated during the year that the 559th Group was using 20 bulldozers, 11 road graders, three rock crushers, and two steamrollers for maintenance and new road construction. As many as 43,000 North Vietnamese or Laotians (most of whom were pressed into service) were also engaged in operating, improving, or extending the system. The rain of ordnance that fell upon the trail peaked during 1969, when 433,000 tons fell on Laos. This was made possible by the close-out of Operation Rolling Thunder and the commencement of Operation Commando Hunt in November 1968. U.S. aircraft were freed for interdiction missions and as many as 500 per day were flying the crowded skies over Laos. By the end of the year, bombing missions over southern Laos had climbed 300 percent, from 4,700 sorties in October to 12,800 in November.

Ho Chi Minh Trail, 1970

This round-the-clock aerial effort was directed by Operation Igloo White, run out of Nakhon Phanom, Thailand. It was composed of three parts: strings of air-dropped acoustic and seismic sensors collected intelligence on the trail; computers at the Intelligence Collection Center (ICS) in Thailand collated the information and predicted convoy paths and speeds; and an airborne relay and control aircraft which received the signals from the sensors and routed aircraft to targets as directed by the ISC. This effort was supported by SOG recon teams, who besides carrying out recon, wiretap, and bomb damage assessment missions for Commando Hunt also hand-emplaced sensors for Igloo White. One interesting aspect of the U.S. effort was that the task of personnel interdiction was abandoned by early 1969. The sensor system was not sophisticated enough to detect enemy personnel, so the effort was given up until the advent of Operation Island Tree in late 1971. One shocking revelation for American intelligence analysts during late 1968 was the discovery of a petroleum pipeline running southwest from the North Vietnamese port of Vinh.

By early the following year, the pipeline had crossed the Laotian frontier through the Mu Gia Pass and, by 1970, it reached the approaches to the A Shau Valley in South Vietnam. The plastic pipeline, assisted by numerous small pumping stations, managed to transfer diesel fuel, gasoline, and kerosene all through the same pipe. Thanks to the efforts of the PAVN 592nd Pipelaying Regiment, the number of pipelines entering Laos would increase to six during that year.

The 559th Group was made the equivalent of a Military Region during 1970 and was once again placed under the command of General Dong Sy Nguyen. Under his leadership the unit was reorganized into five divisional headquarters, the 470th, 471st, 472nd, 473rd, and the 571st. The group consisted of four truck transportation regiments, two petroleum pipeline regiments, three anti-aircraft artillery (AAA) regiments, eight engineer regiments, and the 968th Infantry Division. By the close of the year, the 559th was running 27 Binh Trams that transported 40,000 tons of supplies with a 3.4 percent loss rate during the year.

These supplies traveled in convoys from North Vietnam in relays, with trucks shuttling from only one way-station to the next. The vehicles were then unloaded and reloaded onto "fresh" trucks at each station. If a truck was disabled or destroyed, it was replaced from the assets of the next northern station and so on until it was replaced by a new one in North Vietnam. Eventually, the last commo-liaison station in Laos or Cambodia was reached and the vehicles were unloaded. The supplies were then either cached, loaded onto watercraft, or man-portered into South Vietnam. Due to the increased effectiveness of Commando Hunt, North Vietnamese transportation units usually took to the roads only at dusk with the peak in traffic coming in the early hours of the morning. As American aircraft came on station, traffic would subside until just before dawn, when fixed-wing gunships and night bombers returned to their bases. The trucks then began rolling again, reaching another peak in traffic around 06:00 as drivers hurried to get into truck parks before sunrise and the arrival of the morning waves of U.S. fighter bombers. By the last phase of Commando Hunt (October 1970 – April 1972), the average daily number of U.S. aircraft flying interdiction missions included 182 attack fighters, 13 fixed-wing gunships, and 21 B-52s.

Evolution of PAVN anti-aircraft weapons. 1965–1972.

The North Vietnamese also responded to the American aerial threat by the increased utilization of heavy concentrations of anti-aircraft artillery. By 1968 this was mainly composed of 37 mm and 57 mm radar-controlled weapons. The next year, 85 and 100 mm guns appeared, and by the end of Commando Hunt, over 1,500 guns defended the system.

Of all the weapons systems utilized against the trail, according to the official North Vietnamese history of the conflict, the AC-130 Spectre fixed-wing gunship was the most formidable adversary. The Spectres "established control over and successfully suppressed, to a certain extent at least, our nighttime supply operations." The history claimed that allied aircraft destroyed 4,000 trucks during the 1970–1971 dry season, of which the C-130s alone destroyed 2,432. A countermeasure to the Spectre was not long in coming, however. On 29 March 1972 a Spectre was shot down on a night mission by a surface-to-air SAM-7 missile near Tchepone. This was the first American aircraft shot down by a SAM that far south during the conflict. PAVN also responded to U.S. nighttime bombing by building the 1,000 kilometer-long Road K or the "Green Road" from north of Lum Bum to lower Laos. During Commando Hunt IV (30 April through 9 October 1971), U.S., South Vietnamese, and Laotian forces began to feel the North Vietnamese reaction to the coup of General Lon Nol in Cambodia and the closure of the port of Sihanoukville to its supply shipments. As early as 1969 PAVN, perhaps anticipating the loss of its southern supply line, began its largest logistical effort of the entire conflict.

The Laotian towns of Attopeu and Saravane, at the foot of the Bolovens Plateau were seized by the North Vietnamese during 1970, opening the length of the Kong River system into Cambodia. Hanoi also created the 470th Transportation Group to manage the flow of men and supplies to the new battlefields in Cambodia. This new "Liberation Route" turned west from the trail at Muong May, at the southern end of Laos, and paralleled the Kong River into Cambodia. Eventually this new route extended past Siem Prang and reached the Mekong River near Stung Treng. During 1971 PAVN took Paksong and advanced to Pakse, at the heart of the Bolovens Plateau region of Laos. The following year, Khong Sedone fell to the North Vietnamese. PAVN also continued a campaign to clear the eastern flank of the trail that it had begun in 1968.

In 1968, U.S. Special Forces camps at Khe Sanh and Kham Duc, both of which were utilized by SOG as forward operations bases for its reconnaissance effort, had either been abandoned or overrun. In 1970, the same fate befell another camp at Dak Seang. What had once been a 20-mile (Bad rounding here km) wide supply corridor now stretched for 90 miles (Bad rounding here km) from east to west.

Road to victory (1971–1975)

In early February 1971, 16,000 (later 20,000) South Vietnamese troops rolled across the Laotian border along Route 9 and headed for the PAVN logistical center at Tchepone. Operation Lam Son 719, the long-sought assault on the Ho Chi Minh trail itself and the ultimate test of the American policy of Vietnamization, had begun. Unfortunately for the South Vietnamese, U.S. forces (with the exception of air support, artillery fire, and helicopter aviation units) were prohibited by law from participation in the invasion. At first the operation went well, with little resistance from the North Vietnamese. By the beginning of March, however, the situation had begun to change. Hanoi had made the decision to stand and fight and it began to muster forces that would eventually number 60,000 men, outnumbering its adversary by almost three to one.

The fighting that erupted in southeastern Laos was unlike any yet seen in the Vietnam War, since the PAVN abandoned its old tactics and launched a conventional counterattack. The North Vietnamese first launched massed infantry attacks supported by armor and heavy artillery to crush South Vietnamese positions on the flanks of the main advance. Coordinated anti-aircraft fire made tactical air support and resupply difficult and costly, as the loss of 108 helicopters shot down and 618 others damaged could attest. North Vietnamese forces then began to squeeze in on the main line of the advance.

Although a heliborne assault managed to seize Tchepone, it was a useless victory, since the South Vietnamese could only hold the town for a short period before being withdrawn due to attacks on the main column. The only way the invasion force managed to extricate itself from Laos was through the massive application of American airpower. By 25 March it was all over. The last South Vietnamese troops recrossed the border, closely followed by their enemy. As a test of Vietnamization, Lam Son 719 had been an abject failure. Approximately one half of the invasion force was lost during the operation. Although the South Vietnamese troops had fought well, they were poorly led. Even worse, their elite Ranger and Airborne elements had been decimated.

Although Lam Son 719 had been a bloody debacle for the allied cause, it had managed to postpone a planned PAVN offensive against the northern provinces of South Vietnam for one year. By the spring of 1972 it was again obvious to the Americans and South Vietnamese that their enemy was planning a major offensive, but they did not know where or when it would take place. The answer came on 30 March when 30,000 PAVN troops, supported by more than 300 tanks crossed the border and invaded Quang Tri Province. The Nguyen Hue Offensive (known to the Americans as the Easter Offensive) was under way. As South Vietnamese forces were on the verge of collapse, President Richard M. Nixon responded by increasing the magnitude of the American aerial assault (due to the withdrawal of U.S. aviation units from Southeast Asia, squadrons were flown into South Vietnam from Japan and the U.S. itself). Regardless, the effort failed to halt the fall of Quang Tri City on 2 May, seemingly sealing the fate of the four northernmost provinces. Due to the adoption of a conventional offensive (and the logistical effort needed to support it), PAVN placed itself squarely in the sights of American air power and its casualties were staggering.

The situation was complicated for the Americans by the launching of two smaller attacks by the North Vietnamese: the first aimed to seize Kontum, in the Central Highlands, and threatened to cut South Vietnam in two; the second prompted a series of savage battles in and around An Loc, the capital of Binh Long Province. A total of 14 North Vietnamese divisions were now committed to the offensive. On 13 May the South Vietnamese launched a counteroffensive with four divisions backed by massive U.S. air support. By the 17th, Quang Tri City was retaken, but the South Vietnamese military then quickly ran out of steam. After fierce combat, the PAVN thrusts against Kontum and An Loc were also contained. During these operations North Vietnamese suffered approximately 100,000 casualties while the South Vietnamese lost 30,000 men killed during the fighting. The seizure of territory within South Vietnam itself, however, allowed Hanoi to extend the trail across the Laotian border and into that country.

The signing of the Paris Peace Accord seemed to bring the conflict in Southeast Asia to an end. The last American forces (and all their aircraft) departed; both the North and South Vietnamese were to maintain control in the areas under their influence; and negotiations between the two nations, possibly leading to a coalition government and unification, were to take place. It was not to be. Jockying for control of more territory, both sides flagrantly violated the cease-fire and open hostilities began anew.

By 1973 the PAVN logistical system was a trail in name only. It generally consisted of a two-lane paved (with crushed limestone and gravel) highway that ran from the mountain passes of North Vietnam to the Chu Pong Massif in South Vietnam. By the next year it was possible to travel a completely paved four-lane route from the Central Highlands all the way to Tay Ninh Province, northwest of Saigon. The single oil pipeline that had once terminated near the Ashau Valley now consisted of four lines (the largest eight inches in diameter) and extended south all the way to Loc Ninh. In July 1973 the 259th Group was redesignated the Truong Son Command, the regimental sectors were converted to divisions, and the binh trams were designated as regiments. By late 1974 forces under the new command included AAA Division 377, Transportation Division 571, Engineering Division 473, the 968th Infantry Division, and sectoral divisions 470, 471, and 472. Command then devolved upon Major General Hoang The Thien.

In December 1974 the first phase of a limited PAVN offensive in South Vietnam began. Its success inspired Hanoi to try for an expanded, yet still limited, offensive to improve its bargaining position with Saigon. In March, General Van Tien Dung launched Campaign 275, the immediate success of which prompted the general to push Hanoi for a final all-out offensive to take all of South Vietnam. After a bloody but ineffective attempt to halt the offensive, Saigon fell to North Vietnamese forces on 30 April 1975.

Notes

Unpublished government documents

• U.S. Military Assistance Command, Vietnam Studies and Observations Group, Annex N, Command History 1965. Saigon, 1966.

Published government documents

• Gilster, Herman L. The Air War in Southeast Asia: Case Studies of Selected Campaigns. Maxwell Air Force Base: AL, Air University Press, 1993.
• Military History Institute of Vietnam. Victory in Vietnam: The Official History of the People's Army of Vietnam, 1954–1975. Trans Merle L. Pribbenow. Lawerence KS: University of Kansas Press, 2002.
• Nalty, Bernard C. The War Against Trucks, Aerial Interdiction in Southern Laos, 1968–1972. Washington DC: US Air Force History and Museums Program, 2005.
• Ngo, Lt. Gen. Quang Truong, The Easter Offensive of 1972. Washington DC:United States Army Center of Military History, 1984.
• Nguyen, Maj. Gen. Duy Hinh, Lam Son 719. Washington DC:United States Army Center of Military History, 1979.
• Tranh, Brig. Gen. Dinh Tho, The Cambodian Incursion. Washington DC:United States Army Center of Military History, 1979.
• Tilford, Earl H., Setup: What the Air Force did in Vietnam and Why. Maxwell Air Force Base, AL: Air University Press, 1991.
• Van Staaveren, Jacob. Interdiction in Southern Laos, 1960–1968. Washington DC: Center for Air Force History, 1993.
• Vongsavanh, Brig. Gen. Soutchay RLG Military Operations and Activities in the Laotian Panhandle. Washington DC:United States Army Center of Military History, 1980.