In February 1971, the Army of the Republic of Vietnam (ARVN) launched an incursion into Laos in an attempt to cut the Ho Chi Minh Trail and destroy North Vietnamese Army (NVA) base areas along the border. This movement would be the first real test of Vietnamization, Pres. Richard Nixon's program to turn the fighting over to South Vietnamese forces as US combat troops were withdrawn. US ground forces would support the operation from within South Vietnam and would pave the way to the border for ARVN troops, and US air support would cover the South Vietnamese forces once they entered Laos, but the South Vietnamese forces would attack on the ground alone.The operation, dubbed Lam Son 719, went very well for the first few days, but as movement became bogged down the NVA rushed reinforcements to the battle and the ARVN forces found themselves under heavy attack. US airpower wreaked havoc on the North Vietnamese troops, but the South Vietnamese never regained momentum and ultimately began to withdraw back into their own country under heavy enemy pressure.In this first in-depth study of this operation, military historian and Vietnam veteran James H. Willbanks traces the details of battle, analyzes what went wrong, and suggests insights into the difficulties currently being incurred with the training of indigenous forces.