 Throughout 1967 and into 1968, the United States Marine Corps units in the northern I Corps region had been tied to their combat bases along the South Vietnam border as part of the McNamara Line.This "line" was a combination of infantry units and ground sensors devised to stop PAVN infiltration into South Vietnam across the border and along the Ho Chi Minh Trail.When Maj. Gen. Raymond G. Davis took command of the 3rd Marine Division, he ordered Marine units to move out of their combat bases and engage the enemy.