25th Division (South Vietnam)

The ARVN defensive arc was quite close to the capital. In the northwestern sector at Củ Chi the Division was only 25km from Tan Son Nhut Air Base. Although only one regiment was usually kept in the Củ Chi area, substantial RF/PF forces gave density and depth to the defenses there. Since this was perhaps the most likely approach to Saigon for armor, extensive antitank ditches were dug near strongpoints. The Division kept one regiment at Tây Ninh Combat Base and the other in the Khiem Hanh-Tri Tam-Boi Loi triangle. Although inside contested territory, these dispositions afforded essential depth to the defense. The trouble was that the PAVN/VC often exercised their capability to interdict the tenuously held routes to the outposts, so that major operations were frequently required to run the resupply convoys, and increasingly heavy burdens were placed on aerial resupply. The PAVN/VC crowded the ARVN defenses with local battalions, as well as main force regiments. Contact was virtually constant in the Ho Bo and Boi Loi areas north of Củ Chi, but an even more serious threat developed in the Long Nguyen, a heavily wooded, long-time PAVN/VC base area in the gap between Củ Chi and the 5th Division at Lai Khê. The PAVN 9th Division pushed into this area from its bases in the Michelin and Minh Thanh plantations and was soon threatening lightly-held RF/PF positions on the northern leg of the Iron Triangle: Rach Bap, Base 82 and An Dien. The southern vertex of the Triangle opposite the village of Phu Hoa and at the confluence of the Saigon and Thi Thien Rivers, was only 26.5km from the runways of Tan Son Nhut and Bien Hoa Air Bases, and maximum range of the PAVN's 130-mm. field gun was 26.7km. A successful crossing of the Thi Thien River below Bến Cát would isolate the 5th Division at Lai Khê, probably result in eliminating the defenses in front of the Bình Dương Province seat at Phú Cường, and place PAVN forces in a position for a rapid move into Saigon.[12]^:43

PAVN strategy in Tây Ninh called for continuing pressure along lines of contact, preventing South Vietnamese forces from probing too deeply into the base area, and undermining the fragile hold on the vital corridor between Tây Ninh City and Saigon. This pressure was exerted from three directions and spilled over prominently into Hậu Nghĩa Province through which the corridor passed into the northwestern suburbs of Saigon. From the Parrot's Beak of Svay Rieng Province PAVN forces probed ARVN outposts along the Vàm Cỏ Đông River. The river port of Go Dau Ha was kept under constant threat. Since the port was the junction of National Routes 1 and 22, only 10km from the Cambodian frontier, its loss would sever Tây Ninh and isolate sizable South Vietnamese forces there. The PAVN prevented any ARVN forays toward its northern Tây Ninh base along local Route 4 which led into the PAVN's growing headquarters, logistical, and political complex around Lò Gò, Thien Ngon, Xa Mát and Katum. Moving within range of the Division's forward base at Tây Ninh Combat Base, the ARVN outpost and communications relay station on Nui Ba Den mountain and the RF base at Soui Da, the PAVN regularly harassed these positions with artillery, mortar, and rocket fire and made resupply of Nui Ba Den hazardous by frequently directing antiaircraft fire and SA-7 missiles at RVNAF helicopters. The PAVN exerted strong pressure against the Tây Ninh-Saigon corridor from its forward combat bases along the Saigon River from the Michelin Plantation to the Ho Bo Woods. In mid-late 1973, the PAVN 101st Regiment was backing up local battalions harassing RF/PF and elements of the Division generally north of Highways 1 and 22. Principal targets for PAVN artillery and mortar attacks were Khiem Hanh, a forward base protecting the northern approach to Go Dau Ha; Trảng Bàng a principal town and defensive position astride Highway 1 midway between Tây Ninh City and Saigon; Củ Chi, the main base of the Division; and the defensive position at Trung Lap north of Highway 1. Although a night rarely passed without some kind of attack against these or smaller posts, major contacts were infrequent. But in one major engagement in late September, the 2nd Battalion, 49th Regiment was caught in a devastating ambush in a rubber plantation between Highway 22 and Khiem Hanh, more than half the battalion were casualties, including 43 killed, and the battalion lost nearly 150 weapons and 18 field radios. Shortly afterward some command changes were made in the Division, including the Division commander and commanders of the 46th and 49th Regiments. The road to recovery was long and slowly travelled for the 49th Regiment, but the 50th Regiment during the last half of 1973, enjoyed more successes than failures in sweep operations around Phú Hòa District and in southeastern Bình Dương and Hậu Nghĩa Provinces. In the only other major contact in the Tây Ninh-Saigon corridor in late 1972, a Hậu Nghĩa RF battalion met a battalion of the PAVN 101st Regiment, reinforced by a local company, northeast of Trảng Bàng, the Hậu Nghĩa battalion collected 32 weapons on the battlefield and buried 56 PAVN soldiers, while RF casualties were 19 killed and 33 wounded.[12]^:75–6

In March 1974 a battalion from each of the 46th and 50th Infantry Regiments were used to break the PAVN siege of Đức Huệ at the start of the Battle of Svay Rieng. Subsequently the 49th Regiment and Ranger forces made the initial sweep of PAVN base areas in Svay Rieng Province and then a Division battalion and 3rd Troop, 10th Armored Cavalry Squadron formed part of Task Force 310 for a sweep into the Angel's Wing (11.03°N 106.163°E / 11.03; 106.163) area of Cambodia.[12]^:93–5

On 2 October 1974 the 2nd Battalion, 46th Infantry was committed to reinforce the 2nd Battalion, 9th Infantry, 5th Division which was fighting to recapture Base 82 in the Battle of the Iron Triangle, the combined force recaptured the base on 4 October. In mid-November the 46th Infantry and one battalion of the 50th Infantry joined the battle in its final phases.[12]^:101–5

In early December 1974 heavy combat in Tây Ninh began, with PAVN rockets falling on the province capital and on adjacent military installations. Although an RF company guarding the radio relay station on the summit of Nui Ba Den began receiving attacks of increasing intensity and frequency, the main PAVN effort was against hamlets and RF outposts along local Route 13 northeast of Tây Ninh City. The PAVN attacked early on 7 December, by noon forces from the 205th Independent Regiment were in the hamlets, although the RF post at Soui Da held on. The 8th and 9th Battalions, 205th Regiment, were on local Route 13 southwest of Soui Da, and the PAVN D-14 and D-16 Tây Ninh Battalions were blocking ARVN relief efforts. Meanwhile, the 7th Battalion, 205th Regiment, in trying to overrun Soui Da, lost over 100 of its soldiers. The RF battalion defending Soui Da captured two PAVN soldiers to confirm the identification of the 205th Regiment in the attack, and one of the RF patrols ambushed and captured a 100mm field gun. The 46th Regiment, pushing a column up Route 13 from Tây Ninh City, did not fare so well. Ambushed on 12 December about 3km short of Soui Da, it suffered heavy casualties. While heavy combat was taking place around Nui Ba Den, the 80-man RF company at the top fought off repeated assaults. Helicopter resupply and evacuation had become impossible, and although the company commander reported sufficient food and ammunition, water was running very short and several severely wounded men required evacuation. PAVN assaults on Nui Ba Den continued throughout December 1974, but the RF Company held on. Meanwhile, by mid-month, the relief column eventually reached Soui Da and found that the besieging PAVN force had withdrawn. RVNAF efforts to resupply the troops on Nui Ba Den were largely unsuccessful. Helicopters were driven off by heavy fires, and fighter-bombers were forced to excessive altitudes by SA-7 and antiaircraft artillery. One F-5A fighter-bomber was shot down by an SA-7 on 14 December. Finally on 6 January 1975, without food and water and with nearly all ammunition expended, the 3rd Company, 314th RF Battalion picked up its wounded and withdrew down the mountain to friendly lines.[12]^:135–6

On 17 January, III Corps launched an operation using the Division to retake Nui Ba Den. While artillery, helicopter gunships and RVNAF fighter-bombers pounded the PAVN position, Ranger patrols searched for PAVN artillery positions in the jungles north of the mountain. An airmobile assault was attempted, but PAVN antiaircraft artillery and small arms fire were effective in preventing the landing. By 26 January it was apparent that retaking Nui Ba Den was beyond the resources available to III Corps. The 46th Regiment, which had moved to the base of the mountain, was withdrawn to Tây Ninh Combat Base and the operation was terminated. Aided by the excellent observation that Nui Ba Den afforded, PAVN artillery continued to shell Tây Ninh City with heavy rockets and 130mm guns until the end of the month when the center was virtually deserted.[12]^:142

A lull settled over Tây Ninh Province as the soldiers and civilians of South Vietnam prepared for Tết, which began on 11 February, but although combat declined, the PAVN was very actively preparing for a major offensive in Tây Ninh and in adjoining Bình Dương and Hậu Nghĩa Provinces. Elements of three PAVN divisions, two separate infantry regiments, and a number of separate battalions, all supported by up to 10 battalions of medium and heavy artillery, moved to positions around Tây Ninh City. The 6th Regiment, 5th Division and at least three local battalions and a separate regiment, were concentrated to the southwest, ready to cut Routes 1 and 22 at Go Dau Ha. The new 3rd Division, fresh from its victory in the Battle of Phước Long, was north of the city, while the veteran 9th Division was around the Michelin Plantation, preparing to assault Tri Tam on the Tay Ninh-Bình Dương boundary. Large convoys of trucks were seen moving supplies and ammunition forward. Faced by a formidable enemy on his western flank as he assumed command in II Corps, General Nguyễn Văn Toàn set about making decisive changes in dispositions and concepts to deal with the threat. To make the Division, which covered an immense front from the Cambodian frontier nearly to the western outskirts of Saigon, more mobile, he gave responsibility for all static posts to Tây Ninh Regional Forces. Eight RF battalions and seven separate RF companies were placed along lines of communication and major approaches to the city, while the three regiments of the Division conducted mobile operations in the forward areas. The 46th Regiment was east and southeast of the city; the 49th Regiment was north of the city, with battalions around Nui Ba Den; while the 50th Regiment was near Khiem Hanh, to the southeast. A company of M41 light tanks and two troops of armored personnel carriers were in reserve near Tây Ninh City, and a reinforced company of the 81st Airborne Rangers conducted deep patrols on Nui Ba Den and into the jungle of War Zone C, north of the mountain. The Division commander, Brig. Gen. Lý Tòng Bá, like General Toàn had a background in armor and was exercising vigorous, personal leadership in the forward areas, urging his troops to patrol more aggressively into the contested area north of the city. In early March the situation was becoming tense in western Bình Dương, at Tri Tam and throughout Tây Ninh Province, but General Toan's fresh approach renewed the confidence of the Division and the Tây Ninh RF/PF.[12]^:142–3

The PAVN offensive began at 03:30 on 11 March when PAVN infantry and tanks overran an RF outpost on Route 239 about 10km west of Tri Tam. At 06:00 an intense artillery and mortar bombardment on Tri Tam was followed by an assault by T-54 tanks and infantry. The Province chief reacted by sending two RF battalions east along Route 239 toward Bến Củi, but they were stopped by heavy fire short of the lost outpost. PAVN tanks were already in the Bến Củi Plantation. Meanwhile, as the day wore on in embattled Tri Tam the RF/PF defenders held on, destroying two T-54s in the town. The main attack was coming from the east, and the ARVN soldiers blew the bridge on Route 239 east of the town. Fighting raged through the night, and as dawn broke on 12 March, the RF/PF still held Tri Tam. However, the 95C and 272nd Regiments, and at least a company of tanks, supported by a regiment of artillery, continued the attack that day and eliminated the last resistance in Tri Tam. Meanwhile General Toàn had dispatched another relief column toward Tri Tam, Task Force 318, composed of tanks and armored personnel carriers from the 3d Armored Brigade, with the 33d Ranger Battalion attached, was stopped by heavy B-40 and 130mm gunfire before it could reach Tri Tam. Three officers, including a company commander, were among the heavy casualties in initial fighting near Bến Củi. With Tri Tam in its possession, the PAVN now controlled the Saigon River corridor from its beginning, near Tong Le Chon, to the ARVN outpost at Rach Bap in the Iron Triangle. The ARVN base at Khiem Hanh was now within easy range of PAVN artillery. Khiem Hanh's principal mission was to prevent major PAVN units from closing on Routes 22 or 1 near the critical river port and road junction at Go Dau Ha. Tri Tam was thus the first important objective in a campaign to isolate Tây Ninh Province from Saigon. On the eve of the assault on Tri Tam three main force Tây Ninh PAVN battalions, the D-14, D-16 and D-18, with support from the 101st Regiment and the 75th Artillery Division closed Highway 22 between Go Dau Ha and Tây Ninh City. The 75th Artillery Division had five regiments operating in Tay Ninh for this campaign, and the 377th Antiaircraft Artillery Division had about 15 antiaircraft battalions, some providing direct support for infantry. While the PAVN Tây Ninh battalions blocked Highway 22 north of Go Dau Ha, the 6th and 174th Regiments, 5th Division, attacked out of Cambodia and struck the ARVN base at Ben Cau, northwest of Go Dau Ha between the international boundary and the Vàm Cỏ Đông River. Initial assaults were repulsed, and two PT-76 tanks were destroyed. When two large concentrations of tanks were sighted west of Go Dau Ha on 12 March, RVNAF fighter-bombers destroyed eight and damaged nine, losing three aircraft in the engagement. Ben Cau, however, fell on 14 March as defending RF/PF pulled back toward Go Dau Ha. Ben Cau was only one of eight outposts west of the Vàm Cỏ Đông River that came under heavy attack on 12 March. Most of them held out until the night of 13 March, but nearly all were in PAVN hands by the next day. General Toàn reacted to the crisis developing at Go Dau Ha by reinforcing at Khiem Hanh and along Routes 1 and 22. He deployed the 3rd Armored Brigade, with its three battalions, reinforced by the 64th and 92nd Ranger Battalions and the 48th Regiment, 18th Division, reinforced with armored personnel carriers (from Corps' reserve in Long Binh) to Khiem Hanh and Go Dau Ha. He also pulled the 3rd Battalion, 7th Regiment from the 5th Division at Lai Khê and sent it to reinforce Khiem Hanh. While a battalion of the 48th Regiment attacked west out of Go Dau Ha to clear Route 1 to the Cambodian frontier, the 46th Regiment attacked north along Route 22 to help RF/PF clear the road to Tây Ninh against heavy resistance and intense artillery fire.[12]^:165–7

The 3rd Battalion, 48th Regiment made contact with a PAVN company west of the Vàm Cỏ Đông River on 17 March, killed 36, and captured a number of weapons. Meanwhile, on Route 26 east of Tây Ninh City, an outpost at Cau Khoi, manned by the 351st RF Battalion, was overrun. The outer defenses of Tây Ninh and Hậu Nghĩa began to crumble rapidly after the fall of Cau Khoi. Following an intense bombardment by 105mm howitzers and 120mm mortars, the 367th Sapper Regiment, 5th Division, seized Đức Huệ on 21 March, advancing PAVN held positions to the Vàm Cỏ Đông southwest of the critical village of Trảng Bàng on Route 1. If the PAVN could take Trảng Bàng, Go Dau Ha and all of Tây Ninh would be isolated. North of the airfield at Tây Ninh was the main outpost on local Route 13. The PAVN struck here on 22 March, and the defenders withdrew to an alternate position, Mo Cong II, to the south. The attack continued on the 23rd and Mo Cong II was lost, compressing the perimeter north of Tây Ninh to less than 10km deep. The eastern prong of the PAVN offensive in Tây Ninh was still pressing against the vital position at Khiem Hanh. Just north of Go Dau Ha, Khiem Hanh was an essential strongpoint preventing the PAVN from reaching Route 1 from the north and seizing Go Dau Ha and Trảng Bàng. From Trảng Bàng, Route I provided a high-speed approach through the Division base at Củ Chi and on to Tan Son Nhut and Saigon. On 23 March, ARVN soldiers and tanks made contact with PAVN forces near Truong Mit, northwest of Khiem Hanh. The PAVN had advanced through Cau Khoi on Route 26. A major battle developed on the 24th and casualties were very heavy on both sides. The 3rd Battalion, 7th Regiment, 5th Division, attached to the Division, lost over 400 men killed, wounded, and missing, and the attacking 271st Regiment, 9th Division, left nearly 200 dead. The artillery, tank, and automatic weapons fire was intense; the 271st was supported by a battalion of 37mm antiaircraft weapons used as field artillery, as well as by the 42nd Artillery Regiment with its 85mm and 122mm guns. The decimated 3rd Battalion was withdrawn from combat and sent to the regimental base at Phú Giáo in Bình Dương Province. As a precaution against being flanked by a strong attack down the Saigon River corridor, General Toàn sent the 2nd Battalion, 7th Regiment, to reinforce Rach Bap, the western anchor of the Iron Triangle. Then General Toàn asked the Chief of the JGS, General Cao Văn Viên, for an Airborne brigade to use in a counterattack at Truong Mit. General Viên refused the request; he could not agree to further dissipating the small general reserve while General Toàn still had a few uncommitted units. Therefore, on 25 and 26 March, the 3rd Armored Brigade, together with elements of the Division, attacked the 271st Regiment at Truong Mit and succeeded in reoccupying the position. Losses were again heavy on both sides. General Toàn then reinforced the defense by sending the headquarters and two battalions of the 48th Infantry, 18th Division, to Khiem Hanh.[12]^:169

In early April General Toàn also returned the battalions of the 7th Regiment fighting on Highway 1 near Go Dau Ha to the 5th Division at Lai Khê. This left the defense of Tây Ninh Province and its lines of communication to the Division, elements of the 3rd Armored Brigade, Rangers and RF/PF.[12]^:172 In mid-April while the Battle of Xuan Loc was ongoing, the JGS and III Corps bolstered the inner defenses of Saigon. General Ba, commanding the Division, put a forward command post with his 50th Regiment at Go Dau Ha. In Tây Ninh City he had the 49th Regiment and the headquarters and one battalion of the 46th Regiment. The balance of the 46th was on Route 22 between Tây Ninh City and Go Dau Ha.[12]^:175