During the first few months of 1967, the Viet Cong (VC) absorbed heavy losses as a result of large-scale search and destroy missions conducted by the United States Army, and it prompted North Vietnamese leaders to review their war strategy in South Vietnam.

Then in September, following a string of attacks on U.S. and South Vietnamese military installations by VC and PAVN troops, Major General John H. Hay decided to temporarily stop conducting large-scale operations until the true intentions of PAVN/VC forces were known.

To disrupt the VC's resting period, General Hay launched Operation Shenandoah II to clear a section of Highway 13 which stretched from Chơn Thành to Lộc Ninh.

However, on 16 October, the 2nd Battalion, 28th Infantry Regiment found a major VC bunker system located south of their night defensive position near the Ong Thanh Stream, and a short fire fight broke out.

To avoid fighting a long battle, the commander of the 2nd Battalion decided to pull back and made preparations for a frontal assault on the next day.

On the morning of 17 October, two rifle companies of the 2nd Battalion returned to the bunker system they had found the previous day, but they were defeated by the VC 271st Regiment which had set up an ambush in anticipation of the American attack.

In the first half of 1967, United States military forces in Vietnam had inflicted losses on the VC, both in terms of infrastructure and manpower, through major ground operations such as Cedar Falls, Junction City and Manhattan.

For North Vietnamese military leaders such as Generals Võ Nguyên Giáp and Nguyễn Chí Thanh, the operations carried out by the Americans in South Vietnam had been disastrous for their forces.

[3] In 1967, the United States expanded their Rolling Thunder bombing campaign, which enabled American airpower to destroy rather than just threaten Hanoi's limited industrial infrastructure.

To achieve that objective at the tactical level, Tra argued that PAVN and VC forces would have to destroy American military units, and cause as many casualties as possible until they got tired and left.

[4]: 346 Following various engagements with the U.S. 1st Infantry Division during the previous months, Colonel Võ Minh Triết, commander of the VC 271st Regiment, was ordered to move his troops into an area known as the Long Nguyen Secret Zone, which was situated between National Highway 13 and the Michelin Rubber Plantation.

For that reason Hay was determined to disrupt the VC's resting period by launching Operation Shenandoah II, with the objective of clearing Highway 13 from Chon Thanh to Loc Ninh.

On 2 October, an Army of the Republic of Vietnam (ARVN) unit operating east of Highway 13 near Chon Thanh made significant contact with a large VC formation and absorbed heavy casualties.

[2]: 27  Meanwhile, on 4 October 1/2nd Infantry made contact with a company-sized VC formation about 9 kilometers (5.6 mi) south-west of Chon Thanh, and claimed to have killed 12 enemy soldiers.

[4]: 350 At around 18:00, the rain began to fall and the VC started attacking the 1/18th Infantry's position from different directions, but Cavazos' men were able to hold their ground, with the support of artillery and mortar fire.

[4]: 353–354 On the morning of 16 October, Allen led Companies B and D, 2/28th Infantry out from their temporary night defensive position along the Ong Thanh Stream to patrol an area to the southeast, which was covered by thick jungle canopy.

Again, Allen ordered his men to pull back and form a perimeter to protect their wounded soldiers, as artillery strikes were called in against VC bunker positions.

[1] Meanwhile, the 1,200-strong 271st Regiment was joined by 200 soldiers from the C1 Company of Rear Service Group 83, under the command of Captain Nguyễn Văn Lém, and they set up a three-sided ambush and waited for the arrival of a reported U.S.

In accordance with the 1st Brigade's policy, Allen personally led his unit out as part of the Battalion Command Group, although he preferred to supervise actions from a helicopter.

A claymore mine then exploded in front of Company A's command element, killing the radio operator and severely wounding both George and his forward artillery observer.

[4]: 357 To break contact with the VC units which fired on Company A from the western flank, First sergeant Jose Valdez quickly organized an assembly area on the eastern side to round up the survivors.

Forward Observer Second lieutenant Harold B. Durham, who was attached to the battalion on the day from the 15th Field Artillery Regiment, was posthumously awarded the Medal of Honor for his heroic actions.

[6]: 41 Despite the losses that had been inflicted on the 2nd Battalion by the VC, the U.S. military told the media that the fight at Ong Thanh had resulted in a major American victory.

[2]: 341  For retired U.S. Army Brigadier general James E. Shelton, who was then a major and served as an Operations Officer with the 2/28th Infantry, the lack of reliable intelligence and overconfidence on the part of Allen as the battalion commander, were some of the factors that led to the disastrous outcome in the Ong Thanh battle.

[6] Meanwhile, the rest of the VC 9th Division was planning for a major attack on Loc Ninh, with the objective of capturing the district town and the Special Forces Camp.