Operation Lam Son 719 Operation Lam Son 719 ( ) was a limited - objective offensive campaign conducted in southeastern portion of the Kingdom of Laos by the armed forces of the Republic of Vietnam ( South Vietnam ) between 8 February and 25 March 1971 , during the Vietnam War . The United States provided logistical , aerial , and artillery support to the operation , but its ground forces were prohibited by law from entering Laotian territory . The objective of the campaign was the disruption of a possible future offensive by the People ' s Army of Vietnam ( PAVN ) , whose logistical system within Laos was known as the Ho Chi Minh Trail ( the Truong Son Road to North Vietnam ) . By launching such a spoiling attack against PAVN ' s long - established logistical system , the American and South Vietnamese high commands hoped to resolve several pressing issues . A quick victory in Laos would bolster the morale and confidence of the Army of the Republic of Vietnam ( ARVN ) , which was already high in the wake of the successful Cambodian Campaign of 1970 . It would also serve as proof positive that South Vietnamese forces could defend their nation in the face of the continuing withdrawal of U . S . ground combat forces from the theater . The operation would be , therefore , a test of that policy and ARVN ' s capability to operate effectively by itself . Because of the South Vietnamese need for security which precluded thorough planning , an inability by the political and military leaders of the U . S . and South Vietnam to face military realities , and poor execution , Operation " Lam Son 719 " collapsed when faced by the determined resistance of a skillful foe . The campaign was a disaster for the ARVN , decimating some of its best units and destroying the confidence that had been built up over the previous three years . Background . Between 1959 and 1970 , the Ho Chi Minh Trail had become the key logistical artery for PAVN and the National Front for the Liberation of South Vietnam ( NLF or commonly , " Viet Cong " ) , in their effort to conduct military operations to topple the U . S . - supported government of South Vietnam and create a unified nation . Running from the southwestern corner of the Democratic Republic of Vietnam ( North Vietnam ) through southeastern Laos and into the western portions of South Vietnam , the trail system had been the target of continuous U . S . aerial interdiction efforts that had begun in 1966 . Only small - scale covert operations in support of the air campaigns had , however , been conducted on the ground inside Laos to halt the flow of men and supplies on the trail . Since 1966 , over 630 , 000 men , 100 , 000 tons of foodstuffs , 400 , 000 weapons , and 50 , 000 tons of ammunition had traveled through the maze of gravel and dirt roads , paths , and river transportation systems that crisscrossed southeastern Laos and which linked up with a similar logistical system in neighboring Cambodia known as the Sihanouk Trail . However , following the overthrow of Prince Norodom Sihanouk in 1970 , the pro - American Lon Nol regime had denied the use of the port of Sihanoukville to communist shipping . Strategically , this was an enormous blow to the North Vietnamese effort , since 70 percent of all military supplies that supported its effort in the far south had moved through the port . A further blow to the logistical system in Cambodia had come in the spring and summer of 1970 , when U . S . and ARVN forces had crossed the border and attacked PAVN / NLF Base Areas during the Cambodian campaign . With the destruction of the North Vietnamese logistical system in Cambodia complete , the U . S . headquarters in Saigon determined that the time was propitious for a similar campaign in Laos . If such an operation were to be carried out , the U . S . command believed , it would be best to do it quickly , while American military assets were still available in South Vietnam . Such an operation would create supply shortages that would be felt by PAVN / NLF forces 12 – 18 months later , as the last U . S . troops were leaving South Vietnam and thereby give the U . S . and its ally a respite from a possible communist offensive in the northern provinces for one year , possibly even two . There were increasing signs of heavy communist logistical activity in southeastern Laos , activity which heralded just such a North Vietnamese offensive . Communist offensives usually took place near the conclusion of the Laotian dry season ( from October through March ) and , for PAVN logistical forces , the push to move supplies through the system came during the height of the season . One U . S . intelligence report estimated that 90 percent of PAVN materiel coming down the Ho Chi Minh Trail was being funneled into the three northernmost provinces of South Vietnam , indicating forward stockpiling in preparation for offensive action . This build - up was alarming to both Washington and the American command , and prompted the perceived necessity for a spoiling attack to derail future communist objectives . Planning . On 8 December 1970 , in response to a request from the Joint Chiefs of Staff , a highly secret meeting was held at the Military Assistance Command , Vietnam ' s ( MACV ) Saigon headquarters to discuss the possibility of an ARVN cross - border attack into southeastern Laos . According to General Creighton W . Abrams , the American commander in Vietnam , the main impetus for the offensive came from Colonel Alexander M . Haig , an aide to National Security Advisor Dr . Henry Kissinger . MACV had been disturbed by intelligence of a PAVN logistical build - up in southeastern Laos but was reluctant to let the ARVN go it alone against the North Vietnamese . The group ' s findings were then sent on to the Joint Chiefs in Washington , D . C . By mid - December , President Richard M . Nixon had also become intrigued by possible offensive actions in Laos and had begun efforts to convince both General Abrams and the members of his cabinet of the efficacy of a cross - border attack . Abrams felt that undue pressure was being exerted on Nixon by Haig , but Haig later wrote that the military was lacking in enthusiasm for such an operation and that " prodded remorselessly by Nixon and Kissinger , the Pentagon finally devised a plan " for the Laotian operation . Other possible benefits which might accrue from such an operation were also being discussed . Admiral John S . McCain Jr ( CINCPAC ) communicated with Admiral Thomas Moorer , chairman of the Joint Chiefs , that an offensive against the Ho Chi Minh Trail might compel Prince Souvanna Phouma , prime minister of Laos , " to abandon the guise of neutrality and enter the war openly . " On 7 January 1971 MACV was authorized to begin detailed planning for an attack against PAVN Base Areas 604 and 611 . The task was given to the commander of U . S . XXIV Corps , Lieutenant General James W . Sutherland , Jr . , who had only nine days to submit it to MACV for approval . The operation would consist of four phases . During the first phase U . S . forces inside South Vietnam would seize the border approaches and conduct diversionary operations . Next would come an ARVN armored / infantry attack along Route 9 toward the Laotian town of Tchepone , the perceived nexus of Base Area 604 . This advance would be protected by a series of leap - frogging aerial infantry assaults to cover the northern and southern flanks of the main column . During the third phase , search and destroy operations within Base Area 604 would be carried out and finally , the South Vietnamese force would retire either back along Route 9 or through Base Area 611 and exit through the A Shau Valley . It was hoped that the force could remain in Laos until the rainy season was underway at the beginning of May . Because of the notorious laxity of the South Vietnamese military when it came to security precautions and the uncanny ability of communist agents to uncover operational information , the planning phase lasted only a few weeks and was divided between the American and Vietnamese high commands . At the lower levels , it was limited to the intelligence and operational staffs of ARVN ' s I Corps , under Lieutenant General Hoang Xuan Lam , who was to command the operation , and the XXIV Corps , headed by General Sutherland . When Lam was finally briefed by MACV and the South Vietnamese Joint General Staff in Saigon , his chief of operations was forbidden to attend the meeting , even though he had helped to write the very plan under discussion . At this meeting , Lam ' s operational area was restricted to a corridor no wider than 15 miles on either side of Route 9 and a penetration no deeper than Tchepone . Command , control , and coordination of the operation was going to be problematic , especially in the highly politicized South Vietnamese command structure , where the support of key political figures was of paramount importance in promotion to and retention of command positions . Lieutenant General Le Nguyen Khang , the Vietnamese Marine Corps commander and protege of Vice President Nguyen Cao Ky , whose troops were scheduled to participate in the operation , actually outranked General Lam , who had the support of President Nguyễn Văn Thiệu . The same situation applied to Lieutenant General Du Quoc Dong , commander of ARVN Airborne forces also scheduled to participate in the operation . After the incursion began , both men remained in Saigon and delegated their command authority to minor officers rather than take orders from Lam . This did not bode well for the success of the operation . Individual units did not learn about their planned participation until 17 January . The Airborne Division that was to lead the operation received no detailed plans until 2 February , less than a week before the campaign was to begin . This was of crucial importance , since many of the units , particularly the Airborne and the Marines , had worked as separate battalions and brigades and had no experience maneuvering or cooperating in adjoining areas . According to the assistant commander of the U . S . 101st Airborne Division , " Planning was rushed , handicapped by security restrictions , and conducted separately and in isolation by the Vietnamese and the Americans . " The U . S . portion of the operation was to bear the title " Dewey Canyon II " , named for the original operation conducted by U . S . Marines in the northwestern South Vietnam in 1969 . It was hoped that the reference to the previous operation would confuse Hanoi as to the actual target of the proposed incursion . The ARVN ' s portion was given the title " Lam Son 719 " , after the village of Lam Son , birthplace of the legendary Vietnamese patriot Lê Lợi , who had defeated an invading Chinese army in 1427 . The numerical designation came from the year , 1971 , and the main axis of the attack , Route 9 . The decisions had been made at the highest levels and planning had been completed , but valuable time had been lost . The South Vietnamese were about to begin their largest , most complex , and most important operation of the war . The lack of time for adequate planning and preparation , as well as the absence of any real questioning about military realities and the capabilities of the ARVN were going to prove decisive . On 29 January President Nixon gave his final approval for the operation . On the following day , Operation " Dewey Canyon II " was under way . Operations . Dewey Canyon II . Any offensive planning by the U . S . was , however , limited by the passage on 29 December 1970 of the Cooper - Church Amendment , which prohibited U . S . ground forces and advisors from entering Laos . " Dewey Canyon II " would , therefore , be conducted within territorial South Vietnam in order to reopen Route 9 all the way to the old Khe Sanh Combat Base , which had been abandoned by U . S . forces in 1968 . The base would be reopened and would then serve as the logistical hub and airhead of the ARVN incursion . U . S . combat engineers were tasked with clearing Route 9 and rehabilitating Khe Sanh while infantry and mechanized units secured a line of communications along the length of the road . American artillery units would support the ARVN effort within Laos from the South Vietnamese side of the border while Army logisticians coordinated the entire supply effort for the South Vietnamese . Air support for the incursion would be provided by the aircraft of the U . S . Air Force , Navy , and Marine Corps , and U . S . Army aviation units were tasked with providing complete helicopter support for the ARVN operation . U . S . forces earmarked for these missions included : four battalions of the 108th Artillery Group ; two battalions of the 45th Engineer Group ; the 101st Airborne Division ; six battalions of the 101st Aviation Group ; the 1st Brigade of the 5th Infantry Division ( reinforced by two mechanized , one cavalry , one tank , and one airmobile infantry battalions ; and the two battalions of the 11th Infantry Brigade of the 23rd Infantry Division . On the morning of 30 January , armor / engineer elements of the 1st Brigade of the U . S . 5th ( Mechanized ) Infantry Division headed west on Route 9 while the brigade ' s infantry elements were helilifted directly into the Khe Sanh area . By 5 February , Route 9 had been secured up to the Laotian frontier . Simultaneously , the 101st Airborne Division began a feint into the Ashau Valley in order to draw PAVN attention away from Khe Sanh . At the combat base , poor weather , obstacles , land mines , and unexploded ordnance pushed the rehabilitation of the airstrip ( estimated by U . S . engineers at four days ) a week behind schedule . As a response , a completely new airstrip had to be built and the first aircraft arrived on 15 February . PAVN resistance was almost nonexistent , and American casualties were light . With no previous allied presence around Khe Sanh , however , the North Vietnamese had seen no need to maintain large forces in the area . Consequent upon disastrous failure to the ARVN ' s incursion into Laos , the supply base of Khe Sanh was forced once again in early April 1971 to be abandoned under NVA ' s artillery and sapper attacks . However , General Sutherland believed that the advance to Khe Sanh had been a race between American and PAVN forces , and the U . S . had won . In order to preserve the security of the upcoming South Vietnamese operation , General Abrams had imposed a rare press embargo on the reporting of troop movements , but it was to no avail . Communist and non - American news agencies released reports of the build - up and even before the lifting of the embargo on 4 February , speculation concerning the offensive was front page news in the U . S . As had been the case during the Cambodian campaign , the government of Laos was not notified in advance of the intended operation . Prime Minister Souvanna Phouma would learn of the invasion of his supposedly " neutral " nation only after it was under way . Offensive . By early 1971 , North Vietnamese troop strength in the Base Area 604 area was estimated by U . S . intelligence at 22 , 000 men : 7 , 000 combat troops , 10 , 000 personnel in logistical and support units , and 5 , 000 Pathet Lao , all under the command of the newly created " 70th Front " . There were differing views on what the expected reaction of PAVN to the offensive might be . General Abrams believed that unlike Cambodia , the North Vietnamese would stand and fight for the Laotian Base Areas . As early as 11 December he had reported to Admiral McCain that : strong infantry , armor , and artillery formations were in southern Laos . . . formidable air defenses were deployed . . . the mountainous , jungle - covered terrain was an added liability . Natural clearings for helicopter landing zones were scarce and likely to be heavily defended . The bulk of the enemy ' s combat units were in the vicinity of Tchepone and PAVN could be expected to defend his base areas and logistics centers against any allied operation . A prescient CIA study released in December 1970 echoed Abram ' s concerns and was supported by a 21 January memorandum which " was remarkably accurate with respect to the nature , pattern , and all - out intensity of [ PAVN ] reactions . " MACV intelligence , on the other hand was convinced that the incursion would be only lightly opposed . Tactical air strikes and artillery preparations would neutralize the estimated 170 to 200 anti - aircraft artillery weapons believed to be in the area , and the threat posed by PAVN armored units was considered minimal . North Vietnamese reinforcement capability was set at 14 days by two divisions north of the Demilitarized Zone , and it was hoped that diversionary operations would occupy them for the duration of the operation . Unfortunately , when North Vietnamese reinforcements did arrive , they did not come from the north as expected , but from Base Area 611 and the A Shau Valley to the south , where eight regiments , all supported by organic artillery units , were within two weeks marching range . The North Vietnamese were expecting some sort of operation as early as 26 January when the text of an intercepted radio message read " It has been determined that the enemy may strike into our cargo carrier system in order to cut it off . . . Prepare to mobilize and strike the enemy hard . Be vigilant . " The tactical air strikes that were to precede the incursion and suppress known anti - aircraft positions were suspended two days prior to the operation due to poor flying weather . After a massive preliminary artillery bombardment and 11 B - 52 Stratofortress missions , the incursion began on 8 February , when a 4 , 000 - man ARVN armor / infantry task force consisting of the 3rd Armored Brigade and the 1st and 8th Airborne Battalions , advanced west unopposed along Route 9 . To cover the northern flank , ARVN Airborne and Ranger elements were deployed to the north of the main advance . The South Vietnamese 39th Ranger Battalion was helelifted into a Landing Zone ( LZ ) known as Ranger North while the 21st Ranger Battalion moved into Ranger South . These outposts were to serve as tripwires for any communist advance into the zone of the ARVN incursion . Meanwhile , the 2nd Airborne Battalion occupied Fire Support Base ( FSB ) 30 while the 3rd Airborne Brigade Headquarters and the 3rd Airborne Battalion went into FSB 31 . Troops of the 1st Infantry Division simultaneously combat assaulted into LZs Blue , Don , White , and Brown and FSBs Hotel , Delta , and Delta 1 , covering the southern flank of the main advance . The mission of the central column was to advance down the valley of the Se Pone River , a relatively flat area of brush interspersed with patches of jungle and dominated by heights to its north and the river and more mountains to the south . Almost immediately , supporting helicopters began to take fire from the heights , which allowed PAVN gunners to fire down on the aircraft from pre - registered machine gun and mortar positions . Making matters worse for the advance , Route 9 was in poor condition , so poor in fact that only tracked vehicles and jeeps could make the westward journey . This threw the burden of reinforcement and resupply onto the aviation assets . The helicopter units then became the essential mode of logistical support , a role that was made increasingly more dangerous due to low cloud cover and incessant anti - aircraft fire . The armored task force secured Route 9 all the way to Ban Dong ( known to the Americans as A Luoi ) , 20 kilometers inside Laos and approximately halfway to Tchepone . By 11 February A Luoi had become the central fire base and command center for the operation . The plan then called for a quick ground thrust to secure the main objective , but South Vietnamese forces had stalled at A Loui while awaiting orders to proceed from General Lam . Two days later , Generals Abrams and Sutherland flew to Lam ' s forward command post at Dong Ha in order to speed up the timetable . At the meeting of the generals , it was instead decided to extend the 1st Division ' s line of outposts south of Route 9 westward to cover the projected advance . This would take an additional five days . Back in Washington , Secretary of Defense Melvin Laird and the Joint Chiefs tried to refute claims by reporters that the South Vietnamese advance had stalled . At a press conference , Laird claimed that the halt at A Loui was simply a " pause " that was giving ARVN commanders a chance to " watch and assess enemy movements . . . The operation is going according to plan . " Response . Counteroffensive . The communist response to the incursion was gradual . Hanoi ' s attention was riveted on another diversionary maneuver being conducted by a U . S . naval task force off the coast of the North Vietnam . This force conducted all of the maneuvers necessary for the carrying out of an amphibious landing only 20 kilometers off the city of Vinh . Hanoi ' s preoccupation with a possible invasion did not last long . Its B - 70 Corps commanded three divisions in the incursion area , the 304 , 308 , and 320 . The 2nd PAVN Division had also moved up from the south to the Tchepone area and then began to move east to meet the ARVN threat . By early March , Hanoi had massed 36 , 000 troops in the area , outnumbering the South Vietnamese force by two - to - one . The method chosen by PAVN to defeat the invasion was to first isolate the northern firebases by utilizing anti - aircraft artillery . The outposts would then be pounded by round - the - clock mortar , artillery , and rocket fire . Although the ARVN firebases were themselves equipped with artillery , their guns were quickly outranged by PAVN ' s Soviet - supplied 122mm and 130mm pieces , which simply stood off and pounded the positions at will . The defensive edge that could have been provided by the utilization of tactical B - 52 bomber strikes was nullified by the close - in tactics of the communist forces . Massed ground attacks , supported by artillery and armor would then finish the job . As early as 18 February North Vietnamese forces had begun attacks by fire on Rangers North and South . On the following day the attacks shifted to Ranger North . Ground operations against the outpost were conducted by the 102nd PAVN Regiment of the 308th Division supported by Soviet - built PT - 76 and T - 54 tanks . The Rangers held on tenaciously throughout the night . President Thieu , oblivious to the previous nights attacks , and who was visiting I Corps headquarters at the time , advised General Lam to postpone the advance on Tchepone and to shift the focus of the operation toward the southwest . By the afternoon of the 20th , the 39th ARVN Ranger Battalion had been reduced from 500 to 323 men and its commander ordered a retreat toward Ranger South , six kilometers away . Only 109 survivors reached Ranger South by nightfall . Although more than 600 North Vietnamese troops were estimated as killed during the action , casualties in the three - day fight totaled 75 percent of the ARVN battalion . North Vietnamese attention then shifted to Ranger South , where 400 South Vietnamese troops , including 100 survivors of Ranger North , held the outpost for another two days before General Lam ordered them to fight their way five kilometers southeast to FSB 30 . Another casualty of the battle , although an indirect one , was South Vietnamese General Do Cao Tri , commander of III Corps and hero of the Cambodian campaign . Ordered by President Thieu to take over for the outclassed Lam , Tri died in a helicopter crash on 23 February while en route to his new command . That same day FSB Hotel 2 , south of Route 9 also came under an intense artillery / infantry attack . It was evacuated on the following day . FSB 31 was the next ARVN position to fall under the hammer . Airborne Division commander General Dong had opposed stationing his elite paratroopers in static defensive positions and felt that his men ' s usual aggressiveness had been stifled . Vicious PAVN anti - aircraft fire made reinforcement and resupply of the firebase impossible . General Dong then ordered elements of the 17th Armored Squadron to advance north from A Loui to reinforce the base . The armored force never arrived , due to conflicting orders from Generals Lam and Dong that halted the armored advance several kilometers south of FSB 31 . On 25 February the North Vietnamese deluged the base with artillery fire and then launched a conventional armored / infantry assault . Smoke , dust , and haze precluded observation by an American forward air control ( FAC ) aircraft , which was flying above 4 , 000 feet to avoid anti - aircraft fire . When a U . S . Air Force F - 4 Phantom jet was shot down in the area , the FAC left the area of the battle to direct a rescue effort for the downed aircraft crew , sealing the fate of the base . PAVN troops and tanks then overran the position , capturing the ARVN brigade commander in the process . FSB 31 remained under North Vietnamese control at an estimated cost of 250 killed , and 11 PT - 76 and T - 54 tanks destroyed . The Airborne had suffered 155 killed and over 100 captured . FSB 30 lasted only about one week longer . Although the steepness of the hill on which the base was situated precluded armored attack , the North Vietnamese artillery bombardment was very effective . By 3 March the base ' s six 105mm and six 155mm howitzers had been put out of action . In an attempt to relieve the firebase , ARVN armor and infantry of the 17th Cavalry moved out to save their comrades . Within days , North and South Vietnamese tanks had fought the first armored battle of the Vietnam War north of Route 9 . In the five days between 25 February , the day FSB 31 fell , and 1 March , three major engagements took place . With the help of air strikes , ARVN destroyed 17 PT - 76 and six T - 54 tanks at a loss of three of its five M41 tanks and 25 armored personnel carriers ( APC ) s . On 3 March the South Vietnamese column encountered a PAVN battalion without supporting armor and , with the assistance of B - 52 strikes , killed 400 of the northerners . During each of the above mentioned attacks on the firebases and relief column , communist forces suffered horrendous casualties from aircraft and armed helicopter attacks , artillery bombardment , and small arms fire . In each instance , however , they were pressed home with a professional competence and determination that both impressed and shocked those that observed them . According to the official PAVN history , by March the North Vietnamese had managed to amass three infantry divisions ( 2nd , 304th , 308th ) , the 64th Regiment of the 320th Division and two independent infantry regiments ( 27th and 28th ) , eight regiments of artillery , three engineer regiments , three tank battalions , six anti - aircraft battalions , and eight sapper battalions – approximately 35 , 000 troops , in the battle area . On to Tchepone . While the main South Vietnamese column stalled at A Loui for three weeks and the Ranger and Airborne elements were fighting for their lives , President Thieu and General Lam decided to launch an airborne assault on Tchepone itself . Although American leaders and news correspondents had focused on the town as one of " Lam Son 719 " ' s main objectives , the PAVN logistical network actually bypassed the ruined town to the west . If South Vietnamese forces could at least occupy Tchepone , however , Thieu would have a political excuse for declaring " victory " and withdrawing his forces to South Vietnam . There has been some historical speculation as to Thieu ' s original intentions for " Lam Son 719 " . Some believed that he may have originally ordered his commanders to halt the operation when casualties reached 3 , 000 and that he had always wanted to pull out at the moment of " victory " , presumably the taking of Tchepone , in order to gain political capital for the upcoming fall elections . Regardless , the decision was made to make the assault not with the armored task force , but with elements of the 1st Division . That meant that the occupation of the firebases south of Route 9 had to be taken over by Marine Corps forces , which lost even more valuable time . The assault began on 3 March , when elements of the 1st Division were helelifted into two firebases ( Lolo and Sophia ) and LZ Liz , all south of Route 9 . Eleven helicopters were shot down and another 44 were damaged as they carried one battalion into FSB Lolo . Three days later , 276 UH - 1 helicopters protected by Cobra gunships and fighter aircraft , lifted the 2nd and 3rd Battalions of the 2nd Regiment from Khe Sanh to Tchepone – the largest helicopter assault of the Vietnam War . Only one helo was downed by anti - aircraft fire as the troops combat assaulted into LZ Hope , four kilometers northeast of Tchepone . For two days the two battalions searched Tchepone and the immediate vicinity , but found little but the bodies of North Vietnamese soldiers killed by air strikes . PAVN responded by increasing its daily artillery bombardments of the firebases , notably Lolo and Hope . Retreat . Their goal in Laos seemingly achieved , President Thieu and General Lam ordered a withdrawal of ARVN forces beginning on 9 March that was to continue through the rest of the month , destroying Base Area 604 and any supplies discovered in their path . General Abrams implored Thieu to reinforce the troops in Laos and that they keep disrupting the area until the beginning of the rainy season . Unfortunately , the battle was shifting to Hanoi ' s advantage . Anti - aircraft fire remained devastating and the communists had no trouble resupplying or reinforcing their troops in the battle area . As soon as it became evident that ARVN forces had begun a withdrawal , the PAVN increased its efforts to destroy these force before they could reach South Vietnam . Anti - aircraft fire was increased to halt or slow helicopter resupply or evacuation efforts , the undermanned firebases were attacked , and ARVN ground forces had to run a gauntlet of ambushes along Route 9 . Only a well - disciplined and coordinated army can execute an orderly withdrawal in the face of a determined enemy and the South Vietnamese force in Laos was neither . The retreat quickly devolved into a rout . One by one the isolated firebases were closed out or overrun by the North Vietnamese and each withdrawal was costly . On 21 March South Vietnamese Marines at FSB Delta , south of Route 9 , came under intense ground and artillery attacks . During an attempted extraction of the force , seven helicopters were shot down and another 50 were damaged , ending the evacuation attempt . The Marines finally broke out of the encirclement and marched to the safety of FSB Hotel , which was then hastily abandoned . During the extraction of the 2nd ARVN Regiment , 28 of the 40 helicopters participating were damaged . The armored task force fared little better , losing many of its vehicles to breakdowns or ambushes . During the retreat , the task force lost 60 percent of its tanks and half of its APCs . It also abandoned 54 105mm and 28 155mm howitzers . This equipment then had to be destroyed by U . S . aircraft in order to prevent its capture and reuse by the communists . Covering the retreat on Route 9 was the 1st Armored Brigade , which had been assigned to the ARVN Airborne Division . When informed by a prisoner that two North Vietnamese regiments waited in ambush ahead , the commander of the brigade , Colonel Nguyen Trong Luat , notified General Dong of the situation . The Airborne commander airmobiled forces in and cleared the road , but never bothered to inform Colonel Luat . In order to avoid destruction on Route 9 , Luat then ordered the column to abandon the road only five miles from the South Vietnamese border and plunged onto a jungle trail looking for an unguarded way back . The trail came to a dead end at the steep banks of the Se Pone River and the force was trapped . The North Vietnamese closed in and savage rear guard actions ensued . Two bulldozers were finally helelifted into the ARVN perimeter to create a ford , and the survivors of the force crossed into South Vietnam on 23 March . By the 25th , 45 days after the beginning of the operation , the remainder of the South Vietnamese force that had survived had left Laos behind . The forward base at Khe Sanh had also come under increasing artillery bombardment and sapper attacks . On 6 April , the newly re - organized base of Khe Sanh was also forced to be abandoned and Operation " Lam Son 719 " was over . Aftermath . During a 7 April televised speech , President Nixon claimed that " Tonight I can report that Vietnamization has succeeded . " At Dong Ha , South Vietnam , President Thieu addressed the survivors of the incursion and claimed that the operation in Laos was " the biggest victory ever . " Although " Lam Son 719 " had set back North Vietnamese logistical operations in southeastern Laos , truck traffic on the trail system increased immediately after the conclusion of the operation . The American command ' s claims of success were more limited in scope : MACV claimed that 88 North Vietnamese tanks had been destroyed during the operation , 59 by tactical air power . It also fully understood that the operation had exposed grave deficiencies in South Vietnamese " planning , organization , leadership , motivation , and operational expertise . " For the North Vietnamese , the Route 9 – Southern Laos Victory , was viewed as a complete success . The military expansion of the Ho Chi Minh Trail to the west which had begun in 1970 at the expense of Laotian forces , was quickly accelerated . Laotian troops were soon withdrawing toward the Mekong River and a logistical artery 60 miles in width was soon expanded to 90 miles . Another result of the operation was a firm decision by the Politburo of the Lao Dong Party to launch a major conventional invasion of South Vietnam in early 1972 , paving the way for the " Nguyễn Huệ Offensive " , known in the west as the Easter Offensive . During " Lam Son 719 " , the U . S . planners had believed that any North Vietnamese forces that opposed the incursion would be caught in the open and decimated by the application of American aerial might , either in the form of tactical airstrikes or airmobility , which would provide ARVN troops with superior battlefield maneuvering capability . Firepower , as it turned out , was decisive , but " it went in favor of the enemy . . . Airpower played an important , but not decisive role , in that it prevented a defeat from becoming a disaster that might have been so complete as to encourage the North Vietnamese army to keep moving right into Quang Tri Province . " The number of helicopters destroyed or damaged during the operation shocked the proponents of U . S . Army aviation and prompted a reevaluation of basic airmobile doctrine . The 101st Airborne Division alone , for example , had 84 of its aircraft destroyed and another 430 damaged . Combined U . S . / ARVN helicopter losses totaled 168 destroyed and 618 damaged . During " Lam Son 719 " American helicopters had flown more than 160 , 000 sorties and 19 U . S . Army aviators had been killed , 59 were wounded , and 11 were missing at its conclusion . South Vietnamese helicopters had flown an additional 5 , 500 missions . U . S . Air Force tactical aircraft had flown more than 8 , 000 sorties during the incursion and had dropped 20 , 000 tons of bombs and napalm . B - 52 bombers had flown another 1 , 358 sorties and dropped 32 , 000 tons of ordnance . Seven U . S . fixed - wing aircraft were shot down over southern Laos : six from the Air Force ( two dead / two missing ) and one from the Navy ( one aviator killed ) .