Battle of the Iron Triangle

The Iron Triangle was an important strategic location, bounded on the north by the jungle and overgrown rubber plantations of the Long Nguyen Secret Zone, on the west by the Saigon River and on the east by the smaller but unfordable obstacle of the Thi Thinh River. Phú Cường, the capital of Bình Dương Province, was an important industrial and farming center and contained the ARVN Engineer School. It was linked by a major highway with the large ARVN Phu Loi Base Camp and, farther east, with Bien Hoa Air Base. Lying as it did in the center of the Saigon River corridor, at the junction of Highways 13 and 1, and only 16 km from the outskirts of Saigon, Phú Cường was vital to the defense of Saigon. The terrain within the Iron Triangle was flat, almost featureless, and covered by dense brush and undergrowth. The clearings, especially in the northern part, were thick with elephant grass, higher than a man's head. The surface was scarred by countless bomb and shell craters so that vehicular movement off the narrow, rough dirt roads was nearly impossible; even tracked vehicles had difficulty. A vast network of tunnels and trenches, most of them caved-in and abandoned, laced this ground that had been the scene of battles since the First Indochina War. A weak string of three ARVN outposts protected the northern edge of the Triangle, from Rach Bap () on the west, close by the Saigon River, along local Route 7 to An Dien () on the Thi Thinh River opposite Bến Cát. Each of these outposts, including Base 82 (), which was midway between Rach Bap and An Dien, was manned by a company of the 321st Regional Force (RF) Battalion. Another country road passed by the Rach Bap outpost, local Route 14, which generally paralleled the Saigon River from Tri Tam, through Rach Bap, and veered to the southeast through the Triangle, crossing the Thi Thinh River before it joined Highway 13 north of Phú Cường. The PAVN had blown the bridge on Route 14 over the Thi Thinh a few weeks earlier, but the stream could be spanned by pontoon sections. About midway between Rach Bap and the Thi Thinh crossing of Route 14, the ARVN had another small firebase. Frequent sweeps and some semi-fixed defensive positions north of Củ Chi manned by the ARVN 25th Division and Hậu Nghĩa Province RF screened the western flank of the Triangle, but PAVN resistance in the Ho Bo Woods opposite Rach Bap and the formidable obstacle of the Saigon River, as well as a lack of resources, limited the influence that the 25th could exert on the situation within the Triangle. The ARVN was strong with infantry, armor, and mutually supporting fire bases and outposts in Bến Cát District east of the Thi Thinh boundary of the Triangle, but only one bridge, a weak span, connected the district town and the Triangle hamlet of An Dien. ==Battle==

PAVN attack On 16 May the PAVN 9th Division began their attack on with heavy artillery, rocket, and mortar concentrations falling on Rach Bap, Base 82 and An Dien. The RF company at Base 82 abandoned its bunkers, many of which had collapsed under the weight of the bombardment, late that afternoon. Rach Bap held out until about 03:00 on 17 May, its surviving defenders withdrawing in the direction of An Dien. The fighting was fierce in An Dien on the 16th, but by the night of 17 May, PAVN forces held the flattened village and its defenses. Remnants of an RF battalion, however, held the western end of the Thi Thinh bridge in a shallow blocking position, while the eastern end, by Bến Cát, was secured by ARVN forces. The PAVN dug in around An Dien but was unable to dislodge the RF positions at the bridge. Two infantry regiments of the 9th Division, with about 10 T-54 and PT-76 tanks, were employed against the dispersed 321st RF Battalion. The 2nd Regiment overran Rach Bap and continued the attack south into the Triangle along Route 14, while the 95C Regiment attacked Base 82 and An Dien. The 271st Regiment was held in reserve. With victory seemingly so close, Thuần was deeply disappointed by the rout of the 8th Regiment, and his disappointment changed to anger when he learned of the relatively light casualties suffered by the 8th: six killed, 29 missing and 67 wounded. But even if the 8th Infantry leaders on the scene could have held their troops in their exposed positions in front of Base 82, the regiment probably could not have survived the PAVN counterattack. In any case, Thuần ordered an immediate investigation of the circumstances of the 8th Infantry's failure and subsequently dismissed the regimental commander. On 11 September, the 8th Infantry was replaced by the 9th, and all three battalions of the 9th Infantry moved into position on the west slope of Hill 25. Combat losses since the start of the PAVN offensive in May, combined with the slow flow of the replacements into the regiment, had reduced battalion strength to under 300. Between 12 and 18 September, the 9th concentrated on reconnaissance, planning, and improvement of positions. As the 9th Regiment prepared for the attack, the PAVN was beginning to execute another relief in the Bến Cát battlefield. The 141st Regiment made preparations to leave the Base 82 area and turn over its defense once again to the 95C Regiment. With the 2nd Armored Cavalry Squadron protecting the right (north) flank, and two Ranger battalions protecting the left, the 9th Infantry Regiment began its attack toward Base 82. The two attacking battalions, the 3rd Battalion on the right, north of Route 7, and the 2nd on the left, crossed the line of departure on Hill 25 on 19 September. Moving slowly, with excellent reconnaissance and effective artillery support, the ARVN methodically eliminated, one by one, the PAVN's mutually supporting bunkers that lay in a dense pattern all along the route of advance. Although the PAVN defended tenaciously and their artillery support was heavy and accurate, they gradually gave ground. On 29 September, the 1st Battalion relieved the 3rd Battalion, and the attack continued. On 2 October, the 2nd Battalion, 46th Infantry was committed to reinforce the 2nd Battalion, 9th Infantry. Before midnight on 3 October, as PAVN artillery and mortars were still firing heavy barrages, a 12-man assault team from the 1st Battalion, 9th Infantry, attempted to breach the barbed wire and scale the earthen wall. An antipersonnel mine detonated, disclosing the team's position and heavy fire from the base pinned it down. Very early the next morning, the PAVN counterattacked, forcing the withdrawal of the assault team. But it became apparent to the ARVN commander on the ground that victory was within grasp. A 100-round concentration of 155-mm. howitzer fire which he requested, had the desired effect: PAVN resistance and return fire was notably diminished by 13:00, and 30 minutes later PAVN infantrymen were seen climbing out of their crumbling fortress and running to the rear. At 15:00 on 4 October the 1st Battalion, 9th Regiment, raised South Vietnam's flag over Base 82, ending a bitter four-month struggle. Rach Bap Following the withdrawal from Base 82 COSVN organized a new corps headquarters in the Tay Ninh- Binh Long region and designated it the 301st Corps. This corps would soon direct the combat operations of the 7th and 9th Divisions, separate regiments, and additional formations already en route from North Vietnam. Meanwhile, Thuần decided to rest the tired troops of the 5th Division and turned his attention to sending his 25th Division to clear out the PAVN bases in the Ho Bo area west of the Iron Triangle. The ARVN defenses around An Dien and Base 82 were taken over by Regional Forces and Rangers. III Corps Headquarters worked on plans to resume the attack to retake Rach Bap, the last outpost still remaining in PAVN hands. Thuần also recognized the need to clean the PAVN out of the southern part of the Iron Triangle around Phu Thu, and a plan encompassing Rach Bap, Phu Thu and the Phú Hòa area west of the Iron Triangle began to take shape. But on 30 October, before the execution of the plan, President Thieu relieved Thuần of command of III Corps and replaced him with Lieutenant general Dư Quốc Đống. Đống immediately surveyed the situation in the Iron Triangle and reviewed the plan of his predecessor, which as modified became Operation Quyet Thang 18/24 (Will to Victory). Battalions from all three divisions of the Corps were committed; D-Day was 14 November. The 9th Infantry, 5th Division started from An Dien and marched west, along Route 7, past Base 82 toward Rach Bap. The 48th and 52nd Regiments, 18th Division crossed the Thi Thinh River south of Ben Cat and entered the Iron Triangle and attacked west toward the Saigon River. Elements of the 50th Infantry, 25th Division, were already in this area. Meanwhile, the 46th Infantry and one battalion of the 50th moved into the plantations north of Phú Hòa District Town to prevent PAVN infiltration across the Saigon River. Along Route 7, the 9th Infantry advanced without incident until 19 November when sharp fighting west of Base 82 resulted in over 40 ARVN soldiers wounded. The PAVN withdrew leaving 14 dead and many weapons and radios behind. The next morning, Reconnaissance Company, 9th Infantry, entered Rach Bap unopposed. The Iron Triangle campaign was virtually over, although mopping-up operations continued in the south along Route 14 until 24 November. Measured against the costs and violence of the earlier phases of the campaign, this final chapter was anticlimactic. Casualties on both sides were light, and contacts were few and of short duration. The PAVN had given up its last foothold in the Iron Triangle with only token resistance in order to replace losses, reorganize, re-equip and retrain the main forces of the new 301st Corps for the decisive battles to come. ==Aftermath==

The drawn out fighting over the small battlefield of the Iron Triangle, while ending in South Vietnamese victory, showed that the North Vietnamese had achieved combat parity and were pushing against the ARVN's outer line of defense around Saigon. ==References==