Operation Imperial Lake was a U.S. Marine Corps, Republic of Korea Marine Corps and U.S. Army operation in the Quế Sơn District, Quảng Nam Province, South Vietnam that took place from 1 September 1970, to 7 May 1971. It was the last operation of the 1st Marine Division during the Vietnam War.
Background
The Quế Sơn mountains located approximately south of Danang had long been a People's Army of Vietnam (PAVN) and Viet Cong (VC) base area, and numerous operations had been mounted against the mountains and valley throughout the war. From late June 1970, the 7th Marine Regiment had been rotating reinforced rifle companies on 5-day patrols of the area, which regularly uncovered PAVN/VC positions and engaged in small skirmishes.
On 13 August, Companies I and L, 3rd Battalion, 7th Marines and Company A, 1st Battalion, 5th Marines began Operation Ripley Center in the central Quế Sơn mountains. On 15 August, Company A, 1/5 Marines was withdrawn from the operation and on 24 August, 2nd Battalion, 7th Marines was landed in the area and took over the operation. The Marines uncovered numerous PAVN/VC facilities and killed 25 PAVN/VC and captured eight for no Marine losses. The operation concluded on 31 August.
In August the 1st Marine Division and the 7th Marine Regiment staffs began planning a large operation to pacify the Quế Sơn mountains, which were believed to harbor the PAVN's Front 4 Headquarters, the D3, R20 and V25 Infantry Battalions, the 42nd Reconnaissance Battalion and the 3D, T89 and T90 Sapper Battalions. The plan called for an intensive air and artillery bombardment intended to drive the PAVN/VC into shelters allowing the 2/7 Marines to land at 12 separate landing zones, the 1st Platoon, Company D, 1st Reconnaissance Battalion to establish 3 observations posts, and for the mortar battery of 3rd Battalion, 11th Marines to establish a firebase on Hill 845.
Operation
September to December 1970
After midnight on 31 August, 10 Marines artillery batteries began shelling 53 targets in the Quế Sơn mountains; when the bombardment ended at 06:45 a total of 13,488 shells had been fired. The artillery barrage was immediately followed by two hours of airstrikes and then at 09:00 the first helicopters began landing the Marines. The 2/7 Marines command post was established on Hill 845, now named Landing Zone Vulture (). The Marine landings were unopposed, and they made no contact with the PAVN/VC over the next four days.
On 5 September, Company E pursued a PAVN soldier into a cave in a ravine near LZ Vulture and were met by heavy weapons fire. The other three companies moved to the area and proceeded to engage an estimated 30-50 PAVN in the ravine in close combat over the next three days. On 9 September, after having lost 3 Marines killed in the ravine, the Marines were pulled back to allow air strikes on the area. By 12 September the Marines had pacified the area with the PAVN having been killed, sealed in caves or withdrawn from the ravine. From 14 to 30 September, the Marines killed 14 PAVN/VC in ambushes throughout the operational area.
On 13 September, 3/7 Marines joined the operation landing southwest of the 2/7 Marines position. On 20 September, the 3/7 Marines launched Operation Imperial Lake South, which continued until the end of September with minimal results.
On 16 September, a VC defector led Company E, 2/7 Marines to two base camps of the 91st Sapper Battalion. On 20 September, the Marines found a headquarters and hospital complex in caves and tunnel underneath LZ Vulture and captured two VC medical corpsmen who revealed that the complex had been evacuated after the 31 August bombardment.
On 22 September, Company F, 2/7 Marines left the operation, and on 23 September, Company G, the mortar battery and the 2/7 Marines command group redeployed to Landing Zone Baldy, leaving only Company E in the area of operations and Company I, 3/7 Marines in the Imperial Lake South area of operations.
At the end of September, the 5th Marine Regiment took over the operation from the 7th Marine Regiment, which was redeploying to the United States as part of Operation Keystone Robin Alpha. Company M, 3rd Battalion, 5th Marines replaced Company E, 2/7 Marines at LZ Vulture, while Company L 3/5 Marines replaced Company I 3/7 Marines in the southern area.