Primary Sources: Vietnam War

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 North Vietnamese Army (NVA), 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 NVA'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 NVA 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 NVA, destroying the confidence that had been built up over the previous three years. Wikipedia