Operation Muscatine was a security mission to protect Chu Lai and the neighboring lowlands from several Viet Cong (VC) battalions, and to search for their camps in the hills that ran along the Quảng Tín–Quảng Ngãi border.

As the attack progressed, VC who had sought refuge in the village fled into the blocking positions, where small arms fire and gunships cut them down.

Elements from the Army of the Republic of Vietnam (ARVN) 2nd Division guarded the districts immediately surrounding Quảng Ngai City.

[1]: 487–8 In the wake of Tet, Allied units based near Quảng Ngai City searched the countryside for the enemy forces that had attacked the provincial capital.

The unit typically operated out of the sprawling village of Son My, made up of over a dozen hamlets that dotted the lower coast of the Batangan Peninsula.

Although there was some question as to whether the 48th Battalion was recovering from Tet in the village or in the hills to the northwest, Colonel Barker conducted regular sweeps through Son My looking for the unit.

The Americans rarely caught a glimpse of their foes, in part because the area was riddled with tunnels that the local inhabitants had built to protect themselves and which the VC had turned to their own uses.

[1]: 488–9  The latest intelligence suggested that the headquarters and two companies from the 48th Battalion, some 200 men, had congregated in the hamlet of My Lai (4) and it was also home to some 400 civilians thought to be VC sympathizers.