In late May 1968 US aerial reconnaissance detected a People's Army of Vietnam (PAVN) supply road being constructed through the jungle from the Ho Chi Minh Trail in Laos parallel to, but 15 km south of, Route 9 in an area known as the "Vietnam Salient" where Vietnam protrudes into Laos.
The 3rd Marine Division planned Operation Robin as a two-stage operation, in Operation Robin North the 1st Marine Regiment would attempt to engage the recently infiltrated PAVN 88th and 102nd Regiments of the 308th Division south of Route 9, while in Operation Robin South the 4th Marine Regiment would conduct airmobile operations further south and locate and destroy the PAVN supply road.:321
Operation Robin North
On 2 June the 1st Battalion, 1st Marines conducted a helicopter assault into Landing Zone Robin ( ) 10 km southeast of Khe Sanh and then moved north towards Route 9 in an attempt push the PAVN against the 2nd Battalion, 3rd Marines blocking positions on Route 9. That evening the 2nd Battalion 4th Marines was lifted to Robin from Ca Lu Combat Base. On the morning of 3 June the 1st Battalion, 4th Marines relieved the 2/4 Marines at Landing Zone Robin.:321
The 2/4 Marines boarded helicopters to assault into Landing Zone Loon ( The initial landing at Loon on 3 June was met by the PAVN with small arms, mortar and artillery fire. At 6am on 4 June a company from the PAVN 88th Regiment attacked Company F 2/4 Marines resulting in 2 U.S. and 34 PAVN killed.:322) 4 km west of Robin and approximately 8 km southeast of Khe Sanh.
The 4th Marines headquarters was established at LZ Robin on 4 June and the 1st Battalion, 12th Marines arrived to establish and artillery base. Companies from the 1/4 Marines replaced the 2/4 Marines on Loon on 4 June and the 2/4 Marines were lifted to establish Landing Zone Crow 2 km northeast of Loon.:322
On 5 June Company C 1/1 Marines encountered a PAVN bunker system 4 km south of Route 9, the battle continued until the following afternoon.:322
At 6am on 6 June a PAVN Battalion attacked Landing Zone Loon, after a 2-hour battle that resulted in 154 PAVN dead, the PAVN withdrew under cover of mortar and artillery fire. Due to the steady pressure on Loon it was decided to evacuate the landing zone and during the afternoon the 1/4 Marines were extracted by helicopter. The last HMM-165 CH-46 (#152533) to leave Loon was hit by PAVN anti-aircraft fire and crashed resulting in 13 U.S. killed. The total U.S. losses for their 3 days at Loon was 24 dead and 37 wounded.:322
Operation Robin South
On 6 June the 3rd Battalion, 9th Marines conducted a helicopter assault into a landing zone southeast of Robin and near the eastern end of the PAVN supply road. The Marines found that the road was well constructed, up to 18 ft wide with numerous culverts and the trees overhead tied together to reduce aerial observation. Beside the road were bunkers, hospitals kitchens and storehouses. The 3/9 Marines moved west along the road for several days destroying it and PAVN facilities as they went.:322–3
On 14 June 2/4 Marines were lifted by helicopter onto the PAVN road near the Laos border and moved east to link up with the 3/9 Marines locating and destroying numerous bunkers and stores as they went.:323
Shortly before dawn on 15 June a Battalion of the PAVN 88th Regiment attacked the 3/4 Marines near Lang Hole penetrating the Marine position. The battle continued until 9am when the PAVN withdrew pursued by helicopter gunships. Marine losses were 16 dead and 58 wounded while PAVN losses were 219 dead and 11 captured.:323
On the morning of 18 June the PAVN attacked Company K 3/4 Marines' night defensive position in a daylong battle the Marines with air and artillery support repulsed the PAVN attack resulting in 11 Marines killed and 30 wounded while the PAVN lost 131 killed.:324
- Shulimson, Jack (1988). US Marines in Vietnam: 1968 The Defining Year. History and Museums Division Headquarters United States Marine Corps. p. 320. ISBN 0160491258.
- Kelley, Michael (2002). Where we were in Vietnam. Hellgate Press. pp. 5–306. ISBN 978-1555716257.
- "680606 HMM-165 Vietnam". USMC Combat Helicopter Association. Retrieved 22 November 2014.
- Smith, Charles (1988). U.S. Marines in Vietnam: High Mobility and Standdown 1969. History and Museums Division, Headquarters, U.S. Marine Corps. p. 63. ISBN 978-1494287627.