The Battle of the Iron Triangle took place from 16 May to 20 November 1974, when the People's Army of Vietnam (PAVN) 9th Division captured Rach Bap and An Dien. The Army of the Republic of Vietnam (ARVN) regained the lost towns in a series of costly counterattacks. Background 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