On the evening of 17 November 1965 the Viet Cong (VC) 1st Regiment overran the Regional Force garrison defending the district capital of Hiệp Đức at the mouth of the Quế Sơn Valley.

[1]: 98–100 [2]: 7 On 20 November the 2 ARVN battalions were withdrawn from Hiệp Đức to support a counterattack against a People's Army of Vietnam (PAVN) attack on Thach Tru in southern I Corps.

[1]: 100 [2]: 8 On 4 December III Marine Amphibious Force (III MAF) commander LG Lew Walt met with ARVN I Corps commander Gen. Nguyễn Chánh Thi to discuss the worsening security situation in the Quế Sơn Valley and they agreed to mount a joint operation there to neutralize the VC forces.

At 13:30 the Rangers walked into an ambush by the VC 70th Battalion which was overrun within 15 minutes, losing a third of their men, the remainder withdrew and established a defensive perimeter 1.2 km northwest and called for air support.

At 11:00 HMM-261 helicopters began landing the 2nd Battalion, 1st Marines at the hamlet of Cam La, 8 km southeast of Quế Sơn to seal off any escape route to the south.

During the course of the day Henderson had ordered the Task Force Delta headquarters to move 3 times severely disrupting command and communications.

[1]: 106 [2]: 18–34 On the morning of 11 December BG Platt ordered the 2/7 Marines to capture Hill 407, which they achieved unopposed, while 3/3 Marines searched north of the hill meeting minimal opposition, Platt suspected that the VC had retreated into the Phước Hà Valley, 5 km southeast and running parallel to the Quế Sơn Valley, a known VC base area.

On 13 December, following further B-52 strikes the 2 battalions moved into the valley from the north and south finding large quantities of abandoned supplies and equipment but few VC.