Operation Dewey Canyon II begins as the initial phase of Lam Son 719, the South Vietnamese invasion of Laos that would commence on February 8. The purpose of the South Vietnamese operation was to interdict the Ho Chi Minh Trail, advance to Tchepone in Laos, and destroy the North Vietnamese supply dumps in the area.

In Dewey Canyon II, the vanguard of the U.S. 1st Brigade, 5th Infantry Division began moving from Vandegrift Combat Base along highway Route 9 toward Khe Sanh with an armored cavalry/engineer task force. These units were to clear the way for the move of 20,000 South Vietnamese troops along the highway to reoccupy 1,000 square miles of territory in northwest South Vietnam and to mass at the Laotian border in preparation for Lam Son 719.

U.S. ground forces were not to enter Laos, in accordance with a U.S. congressional ban. Instead they gave logistical support, with some 2,600 helicopters on call to airlift Saigon troops and supplies. In addition, U.S. artillerymen provided long-range artillery fires into Laos from American firebases just inside the South Vietnamese border.