Ho Chi Minh trail The Hồ Chí Minh trail ( known in Vietnam as the " Trường Sơn 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 the Vietcong or " VC " by its opponents ) and the People ' s Army of Vietnam ( PAVN ) , or North Vietnamese Army , during the Vietnam War . It was named by the Americans for North Vietnamese president Hồ Chí Minh . Although the trail was mostly in Laos , the communists called it the Trường Sơn Strategic Supply Route , after the Vietnamese name for the Annamite Range mountains in central Vietnam . According to the United States 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 ) . Parts of what became the trail had existed for centuries as primitive footpaths which 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 Việt 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 ) Võ Bẩm 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 " flipped " its line of communications to the western side of the Trường Sơn mountains . By 1959 , the 559th had 6 , 000 personnel in two regiments alone , the 70th and 71st , not including 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 transporting 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 notion 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 became 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 North Vietnamese to work the trail and the use of motor transport 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 Trọng Tuệ , who 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 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 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 water ' s surface . The weather in southeastern Laos came to play a large role both in the supply effort and in 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 % of per year ) . The sky was usually overcast and temperatures 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 ) . In 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 tonnes 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 tonnes ) over the Trail , far above the Saigon estimate , demonstrating a key problem which arose when discussing the North Vietnamese supply effort and U . S . attempts to halt it . United States officials had only estimates of its enemy ' s capabilities ; various intelligence collection agencies often conflicted with each other . 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 Laos ' s ostensible neutrality . The intricacies of Laotian affairs , and U . S . and North Vietnamese interference in them led to a mutual policy of each ignoring the other , at least in the public eye . However , this didn ' t prevent the North Vietnamese from violating Laos ' s neutrality by protecting and expanding their supply conduit , and by supporting their Pathet Lao allies in their war against the central government . US intervention came in the form of building and supporting a CIA - backed clandestine army in its fight with the Communists and constantly bombing the trail . On 14 December 1964 , the U . S . Air Force ' s " Operation Barrel Roll " carried out the first systematic bombardment of the Hồ Chí 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 " continued 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 " . The request was granted by the Joint Chiefs of Staff , The area fell under the auspices of " Operation Tiger Hound " . Political complications were not the only factors seriously hampering 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 above - mentioned weather patterns . " 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 ; 85 % were judged to be successful . President Johnson then gave authorization for the program , which lasted until July 1972 . 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 enthusiasm from the military and civilian participants in the program , who claimed they were there to " " make mud , not war " " . In some areas it worked , 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 . 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 , the United States Ambassador to Laos became enraged that U . S . personnel had been spotted in uniform at the remote refueling field in Laos . The following day , the three aircraft departed from Udorn filled with tons of a mixture of nitrilotriacetic acid and sodium tripolyphosphate stuffed into cloth bags designed to break apart at impact . The three aircraft 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 provided air cover to the mission . The target itself was a road cut sharply into a hillside on a long traverse . One North Vietnamese gunner manning a 12mm anti aircraft gun engaged the formation from the ridge line up from the road . However , as the C - 130s were below gun level , 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 " spooks " celebrated the successful mission . Two other 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 Ah Shau Valley , also in South Vietnam , but were unsuccessful . The crews had been 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 Captain 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 decided that the experiment didn ' t justify the risk and 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 . In Laos the agency began " Project Pincushion " in 1962 for that reason . The operation evolved into " Project Hardnose " , in which CIA - backed Laotian irregular reconnaissance team operations took place . In October 1965 , General Westmoreland received authorization to launch a U . S . military cross - border recon effort . On 18 November 1965 , the first mission was launched " across the fence " and into Laos by the Military Assistance Command , Vietnam Studies and Observations Group ( SOG ) . This was the beginning of an ever - expanding reconnaissance effort by SOG that would continue the operation was disbanded in 1972 . Another weapon in the American arsenal was unleashed upon the trail on 10 December 1965 , 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 pervaded some official U . S . government histories of the conflict . John Schlight , in his " A War Too Long " , said of 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 . " 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 anti - infiltration efforts of the U . S . the estimated total of PAVN infiltrators for 1966 was between 58 , 000 and 90 , 000 men , including five full enemy regiments . A June 1966 Defense Intelligence Agency ( DIA ) estimate credited the North Vietnamese with of truckable roads within the corridor , at least of which were good enough for year - round use . 1967 saw a change in command of the 559th Group as Senior Colonel ( later General ) Đồng Sỹ Nguyên 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 learned 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 tonnes 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 ) . 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 engaged in operating , improving , or extending the system . In 1969 , 433 , 000 tonnes of ordnance 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 over Laos . By the end of 1968 , bombing missions over southern Laos had climbed 300 percent , from 4 , 700 sorties in October to 12 , 800 in November . 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 " . 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 " Operation Island Tree " in late 1971 . A revelation for U . S . intelligence analysts in late 1968 was the discovery of a petroleum pipeline running southwest from the northern port of Vinh . Early the following year , the pipeline 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 . Due to the efforts of the PAVN 592nd Pipelaying Regiment , the number of pipelines entering Laos increased to six ( 6 ) that year . The 559th Group was made the equivalent of a Military Region in 1970 and again placed under the command of General Đồng Sỹ Nguyên . 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 end of 1970 the 559th was running 27 " Binh Trams " , which transported 40 , 000 tonnes of supplies with a 3 . 4 % 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 . 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 some 4 , 000 trucks during the 1970 – 1971 dry season , of which the C - 130s alone destroyed 2 , 432 trucks . A countermeasure to the Spectre came on 29 March 1972 , when a Spectre was shot down on a night mission by a surface - to - air SAM - 7 missile near Tchepone . This was the first U . S . aircraft shot down by a SAM that far south during the conflict . PAVN responded to U . S . nighttime bombing by building the 1 , 000 kilometer - long Road K ( " 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 General Lon Nol ' s coup in Cambodia and the subsequent closure of the port of Sihanoukville to its supply shipments . As early as 1969 PAVN had begun 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 continued a campaign to clear the eastern flank of the trail that it had begun in 1968 . By 1968 , U . S . Special Forces camps at Khe Sanh and Khâm Đức , 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 wide supply corridor now stretched for from east to west . Road to PAVN 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 incursion . At first the operation went well , with little resistance from the North Vietnamese . By early March 1971 the situation was changing . Hanoi made the decision to stand and fight . It began to muster forces which would eventually number 60 , 000 North Vietnamese troops as well as several thousand allied Pathet Lao troops and Lao irregulars , outnumbering its adversary by almost three to one . The fighting in southeastern Laos was unlike any yet seen in the Vietnam War , since the PAVN abandoned its old hit - and - run 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 , with 108 helicopters shot down and 618 others damaged . North Vietnamese forces 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 of time 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 1971 the last South Vietnamese troops recrossed the border , closely followed by their enemy . As a test of Vietnamization , " Lam Son 719 " failed ; one - half of the invasion force was lost during the operation . South Vietnamese troops were poorly led and the elite Ranger and Airborne elements had been decimated . " Lam Son 719 " did manage to postpone a planned PAVN offensive against the northern provinces of South Vietnam for one year . By spring 1972 the Americans and South Vietnamese realized that the enemy was planning a major offensive , but they did not know where or when . The answer came on 30 March 1972 when 30 , 000 PAVN troops , supported by more than 300 tanks crossed the border and invaded Quảng Trị Province . The " Nguyen Hue Offensive " ( better known as the " Easter Offensive " ) was underway . 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 ) . The effort failed to halt the fall of Quảng Trị 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 U . S . air power and the casualties were high . The situation was complicated for the Americans by the launching of two smaller attacks by the North Vietnamese : the first aimed to seize Kon Tum in the Central Highlands , and threatened to cut South Vietnam in two ; the second prompted a series of savage battles in and around An Lộc , the capital of Bình Long Province . A total of 14 North Vietnamese divisions were now committed to the offensive . On 13 May 1972 , South Vietnam launched a counteroffensive with four divisions backed by massive U . S . air support . By 17 May , Quảng Trị City was retaken , but the South Vietnamese military ran out of steam . The PAVN thrusts against Kon Tum and An Lộc were contained . During these operations , the North Vietnamese suffered approximately 100 , 000 casualties while the South Vietnamese suffered 30 , 000 fatalities during the fighting . The seizure of territory within South Vietnam itself allowed Hanoi to extend the trail across the border with Laos and into that country . The signing of the Paris Peace Accord seemed to bring the conflict in Southeast Asia to an end . The last U . S . forces departed . Both 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 . Jockying for control of more territory , both sides flagrantly violated the cease - fire and open hostilities began anew . By 1973 , the PAVN logistical system 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 1974 it was possible to travel a completely paved four - lane route from the Central Highlands to Tây 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 to Lộc 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 Hoàng Thế Thiện . In December 1974 the first phase of a limited PAVN offensive in South Vietnam began . Its success inspired Hanoi to try for an expanded but still limited , offensive to improve its bargaining position with Saigon . In March , General Văn Tiến Dũng launched " Campaign 275 " , the success of which prompted the general to push Hanoi for a final all - out offensive to take all of South Vietnam . After an ineffective attempt to halt the offensive , Saigon fell to North Vietnamese forces on 30 April 1975 .