The People's Army of Vietnam (PAVN) Base Area 114 was located in the CoBi-Than Tan valley in the western foothills.

On the morning of 2 January, an 8-man patrol from Company A 3rd Reconnaissance Battalion was landed on a hill 8 km southeast of Camp Evans to observe PAVN movement in the CoBi-Than Tan valley, the reconnaissance Marines did not move from their landing zone and failed to set out claymore mines around their perimeter in the belief that they couldn't be observed.

[1]: 81–2 On 7 January marine air and artillery strikes on PAVN bunkers south of Hill 51 resulted in large secondary explosions.

After midnight on 8 January, a Marine night ambush 5 km east of Hill 51 killed five Viet Cong and captured two.

On 23 January 1st Marine Regiment commander Col. Stanley S. Hughes received orders to close down Operation Neosho II the following day and hand over Camp Evans to the 1st Cavalry Division.