Operation Lam Son 719 or 9th Route – Southern Laos Campaign (Vietnamese: Chiến dịch Lam Sơn 719 or Chiến dịch đường 9 – Nam Lào) was a limited-objective offensive campaign conducted in the southeastern portion of the Kingdom of Laos. The campaign was carried out by the armed forces of South Vietnam between 8 February and 25 March 1971, during the Vietnam War. The United States provided logistical, aerial and artillery support for 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 a pre-emptive attack against the 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 that South Vietnamese forces could defend their nation in the face of the continuing Vietnamization withdrawal of U.S. ground combat forces from the theater. The operation would be, therefore, a test of that policy and the ARVN's capability to operate effectively by itself.
However, due to PAVN and the Viet Cong's (VC) intelligence and preparation beforehand, 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 demonstrated continued deficiencies in ARVN military leadership and that the best units of the ARVN could be defeated by the PAVN, destroying the confidence that had been built up over the previous three years.
Between 1959 and 1970, the Ho Chi Minh Trail had become the key logistical artery for the PAVN/VC, 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 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. The trail also 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/VC Base Areas during the Cambodian Campaign.
With the partial destruction of the North Vietnamese logistical system in Cambodia, 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/VC 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 PAVN/VC offensive in the northern provinces for one year, possibly even two.
There were increasing signs of heavy logistical activity in southeastern Laos, activity which heralded just such a North Vietnamese offensive. PAVN 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 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 North Vietnamese objectives.
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 South 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 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." Although technically neutral, the Laotian government had allowed the CIA and U.S. Air Force to conduct a covert war against an indigenous guerrilla insurgency (the Pathet Lao), that was, in turn, heavily supported by North Vietnamese forces.
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 XXIV Corps, Lieutenant General James W. Sutherland, 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. The village was estimated to have had about 1,500 inhabitants in 1960; five years later, half of the residents had fled due to war; Operation Lam Son 719 then destroyed the village and left it deserted. 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. U.S. planners had previously estimated that such an operation would require the commitment of four U.S. divisions (60,000 men), while Saigon would only commit a force less than half that size.