The Battle of the Iron Triangle took place on May 16, 1974, when the 9th Division of the Vietnam People's Army backed by a small contingent of tanks launched an attack on Rach Bap, took possession of An Dien and pushed south towards Phu Cuong.
The ARVN battled with NVA tanks on June 4 and inflicted heavy casualties on the NVA forces. Six weeks after the ARVN regrouped and reinforced they drove the NVA from its stronghold, Rach Bap. The ARVN retook Rach Bap on November 20 unopposed. No US ground forces took part in the 1974 Battle of the Iron Triangle, as most of them had already been withdrawn from the conflict-torn region due to the policy of Vietnamization undertaken by the Nixon Administration in 1969.
With government forces clinging only to a narrow bridge connecting Ben Cat and An Dien, MR3 commander Lieutenant General Pham Quoc Thuan deployed the 18th ARVN Division in a multipronged counterattack designed to recapture all of the lost positions by May 22. The 43d Infantry supported by the 322d Armored Task Force attacked from the south toward Rach Bap and Hill 82. Task Force 318 advanced from the east toward An Dien, while three battalions of the 7th Ranger Group struck from the north toward Hill 82. None of these efforts met with success. By May 28, with the counterattack bogged down, Thuan decided to regroup for a fresh assault. On June 1 spearheaded by the 52d Infantry began a renewed push, which crossed the Thi Tinh River south of Ben Cat then turned north toward An Dien, while other elements of the 18th Division attacked the village over the semi-repaired An Dien bridge. On June 4 government troops battling enemy tanks finally entered An Dien. Although captured NVA soldiers reported terrible casualties among their comrades, the Communists launched a furious counterattack on the night of June 5 to 6 with two reserve battalions. Between June 7 and July 1 the men of the 18th ARVN Division along with supporting armored task forces repeatedly attacked NVA position east, south, and north of Hill 82, only to be driven back by enemy artillery and antitank fire that claimed thousands of government casualties. By the end of the month the troops he had originally committed had been so roughly handled that General Thuan abandoned the attempt to retake Hill 82 until new plans could be devised. Driven back through pouring rain by fierce artillery fire and tank assaults, the task force was replaced by three battalions of the 9th Regiment which began still another assault on September 19. Using effective counterbattery fire and small assault teams, the 1st and 3d Battalions inched forward, eliminating enemy bunkers one by one. Joined on October 2 by a battalion of the 25th ARVN Division, the attackers pounded NVA defenses with salvos of 155MM howitzer fire that forced the remaining enemy soldiers from their shattered earth and log fortress. Finally government soldiers placed their flag atop Hill 82. Six weeks passed while ARVN regrouped and reinforced its battered units before driving the NVA from its last foothold in the Triangle, Rach Bap. In the interim the southern Communist command received instructions from Hanoi to prepare for the offensive strikes to begin at the end of the year. Withdrawing most of its units to base areas farther north, the enemy left behind only token forces. The Battle of the Iron Triangle was over.
Dougan C., Doyle E., Lipsman S., Martland T., Weiss S. (1983) The Vietnam Experience: The False Peace. Boston Publishing Company, USA.