The Battle of Ong Thanh was fought at the stream of that name (Ông Thành) on the morning of 17 October 1967, in Chơn Thành District, at the time part of Bình Dương Province, South Vietnam, today in Bình Phước Province.
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. This prompted North Vietnamese leaders to review their war strategy in South Vietnam. In light of the setbacks which People's Army of Vietnam (PAVN) and VC forces had experienced in early 1967, PAVN General Trần Văn Trà suggested PAVN and VC forces could still be victorious if they inflicted as many casualties as possible on U.S. military units, hoping that the Americans would conclude that the war was too costly and withdraw from Vietnam. Thus, towards mid-1967 the VC 7th and 9th Divisions returned to the battlefield with the objective of inflicting casualties on U.S. military formations in III Corps. On 12 June the U.S. 1st Infantry Division launched Operation Billings to destroy elements of the VC 9th Division, which had built up strength north of Phước Vĩnh Base Camp in War Zone D. When the operation concluded on 26 June the 1st Infantry Division had lost 57 killed while the VC had lost 347 killed. 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 halt large-scale operations until the true intentions of PAVN/VC forces were known. During October the VC 271st Regiment moved into the Long Nguyen Secret Zone to rest and refit for their next major operation. At around the same time Hay launched Operation Shenandoah II to clear a section of Highway 13 which stretched from Chơn Thành to Lộc Ninh.
Starting on 28 September, elements of the 1st Infantry Division were air-lifted into positions around Long Nguyen, but initially only a few contacts were made with the VC. On 16 October, the 2nd Battalion, 28th Infantry Regiment found a major VC bunker system south of their night defensive position near the Ong Thanh Stream, and a short fire fight broke out. To avoid 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, but they were ambushed by the VC 271st Regiment which had deployed in anticipation of the American attack.
Background In the first half of 1967 United States military forces in Vietnam had inflicted major losses on the VC, both in terms of infrastructure and manpower, through large ground operations such as Cedar Falls, Junction City and Manhattan. For North Vietnamese military leaders like Generals Võ Nguyên Giáp and Nguyễn Chí Thanh the operations carried out by the Americans had been disastrous for their forces. The military situation in North Vietnam also prompted North Vietnamese leaders to question their war strategy. The United States expanded their Rolling Thunder bombing campaign, which enabled American airpower to destroy rather than just threaten Hanoi's limited industrial infrastructure. North Vietnamese leaders feared that if the Red River dikes were targeted by the Americans, Hanoi and the surrounding farmlands would be flooded. At the same time, the North Vietnamese government was afraid the VC might split in order to accommodate a resolution with the Saigon government because the U.S.-backed government in the South Vietnam was showing no sign of collapse.
Despite these unfavorable developments, PAVN General Trần Văn Trà believed North Vietnam could still win the war if they pursued a strategy of attrition. The PAVN/VC would have to fight on for as long as possible until the United States recognized the war was unwinnable and disengage from the conflict in Vietnam. To achieve that objective at the tactical level, Tra believed PAVN and VC forces would have to destroy American military units and cause as many casualties as possible. Towards mid-1967 Thanh, who had the VC 7th and 9th Division at his disposal, began executing this plan. In June, U.S. military forces in III Corps detected the build-up of VC troops in northern Phước Vĩnh in War Zone D. To prevent a major enemy attack on Phước Vĩnh, Major general John H. Hay, commander of the 1st Infantry Division, launched Operation Billings with the objective of trapping three VC battalions in War Zone D. On 26 June Operation Billings concluded. The Americans had killed 347 VC and captured one, at a cost of 57 U.S. dead and 197 wounded.
In August the VC 165th Regiment of the 7th Division targeted the Tong Le Chon Special Forces Camp, located southeast of the 1st Infantry Division's area of operations. Just after midnight on 7 August, the 165th Regiment attacked and penetrated the camp, but withdrew after an ammunition bunker exploded. Several more assaults occurred, but on each occasion they were repelled by artillery fire and close air-support. By September the scale of VC and PAVN activities in III Corps had perplexed the U.S. commanders of Military Assistance Command, Vietnam. During this time Hay decided to put an end to his division's large-scale operations, which had proven to be unproductive, until the enemy's real intentions were known. He continued to commit his 2nd Brigade to pacification efforts in southern Bình Dương Province, while the 3rd Brigade provided protection for engineers clearing Highway 13.
Following a number of small 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 situated between National Highway 13 and the Michelin Rubber Plantation. It was located about northwest of Saigon, in Bình Dương Province. Triết's regiment was supposed to receive troop replacements and food supplies to prepare for a major offensive against an unspecified target in War Zone D. The VC 9th Division had often used the months of September and October to rest and prepare for their winter-spring offensives, and 1967 was no different. 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.
Shenandoah II
On 29 September Hay ordered Colonel George E. Newman—commander of the 1st Brigade—to move the 1st Battalion, 2nd Infantry Regiment and the 1/28th Infantry Regiment to the northern portion of Long Nguyen. The next day Colonel Frank E. Blazey, commander of the 3rd Brigade, was ordered to deploy the 2/2nd Infantry and the 2/28th Infantry to the southern half of the area. In the early stages of Shenandoah II U.S. forces only made a few contacts with the VC. 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 took heavy casualties. Enemy documents captured by the ARVN indicated they had clashed with a battalion-sized unit from the VC 272nd Regiment sent to attack Chơn Thành to cover the movement of the 271st Regiment into the Long Nguyen area. Early in October the 271st Regiment arrived in Long Nguyen but they could not obtain their much-needed food supplies. The earlier allied search-and-destroy operations had created significant food shortages for VC units in the region.
Triet then moved his starving soldiers southward toward the Ong Thanh Stream to link up with Rear Service Group 83, but local VC units also lacked adequate food supplies of their own, so the 271st Regiment was forced to wait in the area for the arrival of rice and other essential supplies. Meanwhile, on 4 October 1/2nd Infantry made contact with a company-sized VC formation about south-west of Chon Thanh, and claimed to have killed 12 enemy soldiers. To pursue the retreating VC formation, Lieutenant colonel Richard E. Cavazos, commander of the 1st Battalion, 18th Infantry Regiment, was instructed to conduct an air-assault into a clearing located about west of 1/2nd Infantry to block enemy troops. 1/18th Infantry landed unopposed and immediately set up a standard field position with wire entanglements to protect the position. On 6 October the 1/18th Infantry position was subjected to a VC mortar bombardment. Even though the attack caused little damage, Cavazos believed it was part of the VC's final preparations for a major ground attack later that evening.
At around 18:00 rain began to fall and the VC started attacking the 1/18th Infantry's position from different directions. Cavazos' men were able to hold their ground with the support of artillery and mortar fire. By midnight the fight was over, and U.S. casualties were five killed and four wounded. Three weeks later, a captured VC soldier from the 2nd Battalion, 271st Regiment revealed that his unit lost 59 soldiers killed and 56 wounded in battle with Cavazos' battalion. On 8 October Hay pulled 1/2nd Infantry back to Phuoc Vinh to serve as the division's reaction force. Lieutenant colonel Terry D. Allen—commander of the 2/28th Infantry—was ordered to depart from Lai Khê with three of his rifle companies (A, B and D) and air-lifted into a site about northwest of Chon Thanh village and north-west of 1/18th Infantry. Company C was detached from Allen's 2/28th Infantry to protect the supporting 15th Field Artillery Regiment.
Two days later, 1/2nd Infantry was deployed into new blocking positions as VC units were believed to be moving toward the Michelin Rubber Plantation. On 11 October two companies of 1/18th Infantry went on a northward probe and were immediately attacked by the VC. While under heavy fire, Cavazos ordered the lead company to pull back behind a perimeter formed by the second company. As the lead company fell back, artillery and air support were called in to pummel the VC attacking formation. When the battle was over, 21 VC were found dead, while U.S. casualties for the day were one killed and four wounded. Shortly afterward 1/18th Infantry pulled back to Phuoc Vinh for rest and refitting. By mid-October Hay believed the VC 271st Regiment had suffered a major defeat and was ready to withdraw from the Long Nguyen Secret Zone, so he was ready to terminate Shenandoah II. Increased VC activity near the Ong Thanh Stream, where the 1st Brigade made most of its contacts, seemed to indicate otherwise.
Battle
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. After marching for about , the battalion found a fortified VC bunker, so Allen ordered his men to pull back and directed airstrikes against VC positions. When the bombing runs were over, Allen's men entered the camp and a firefight broke out with VC snipers firing down from trees in the surrounding areas. 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. The 2nd Battalion re-entered the camp, and they discovered the bodies of 17 VC. Allen's men then moved through the western end of the camp, and another fire-fight broke out with an estimated 60 VC.