Starting in mid-February 1966, patrols detected indications of a pending VC attack against the A Shau Special Forces camp, whose mission was surveillance of infiltration from the nearby Laotian border.
In 1967, the NVA organization in the northwest was under two Military Regions (MR), MR-4 north and south of the DMZ, and MR-5 (also known as MR-S) for Communist units in the northern part of South Vietnam.