During late June and early July 1966, Marine reconnaissance units operating south of the Demilitarized Zone (DMZ) had observed and engaged increased numbers of uniformed regular North Vietnamese Army (NVA) troops. On 6 July, troops of the ARVN 1st Division captured an NVA soldier near The Rockpile who identified himself as being from the 812th Regiment of the 324B NVA Division and advised that the other Regiments of the Division had also moved into South Vietnam. On 9 July a lieutenant from the 812th Regiment surrendered in the same area and advised that the 324B Division's mission was to liberate Quang Tri Province.