 Under I Corps command, but available to Trưởng upon his request were two battalions of the ARVN 1st Airborne Task Force and a troop of armored personnel carriers from the 7th Armored Cavalry Squadron at PK-17, the ARVN base located near a road marker on Highway 1, north of Huế.The Marine's Phu Bai Combat Base, south of Huế on Highway 1, included Task Force X-Ray, a brigade-size component of the 1st Marine Division built around the 1st and 5th Marine Regiments.The U.S. Army 1st and 3rd Brigades, 1st Cavalry Division and the 2nd Brigade, 101st Airborne Division, operated out of a series of firebases and landing zones between Phu Bai and Quảng Trị.