Most of the PAVN/NLF operational capability was possible only because of the unhindered movement of men along the Ho Chi Minh Trail. To threaten this flow of supplies, the Marine Corps established a combat base on the South Vietnamese side of the Laotian frontier, near the village of Khe Sanh. The U.S. used the base as a border surveillance position overlooking Route 9, the only east–west road that crossed the border in the province. Westmoreland also hoped to use the base as a jump-off point for any future incursion against the Trail system in Laos. During the spring of 1967, a series of small-unit actions near Khe Sanh prompted MACV to increase its forces. These small unit actions and increasing intelligence information indicated that the PAVN was building up significant forces just across the border.