Operation Toan Thang IV ("Complete Victory") was a U.S. Army and Army of the Republic of Vietnam (ARVN) operation conducted between 1 November 1969 and 1 May 1970 in the Vietnam War. The operation was designed to keep pressure on Vietcong (VC) and People's Army of Vietnam (PAVN) forces in III Corps.
Background The operation was a continuation of Operation Toan Thang III in the same operational area and with largely the same forces.
Operation November On 19 November a unit of the 3rd Brigade, 9th Infantry Division operating 21 km northwest of Tân An found a munitions cache containing 72 RPG-2 grenades, 106 hand grenades and 5,000 rounds of small arms ammunition. On 21 November a unit of the 1st Cavalry Division (Airmobile) operating near Phước Bình District found a weapons cache containing 39 rifles and four machine guns. On 29 November helicopters from the 2nd Brigade, 1st Cavalry Division and tactical airstrikes kill 69 PAVN/VC.
December On 1 December at 18:50, Rangers from the 3rd Brigade, 9th Infantry Division, engaged 20 PAVN/VC south of Tân An, killing five and capturing one.
On 2 December at 04:00, a unit of the 11th Armored Cavalry Regiment (11th ACR) engaged an enemy force approaching its night defensive position southwest of Bù Đốp District. The enemy withdrew after five minutes, leaving seven dead; U.S. losses were two killed. At 09:30 mechanized infantry of the 1st Brigade, 25th Infantry Division, investigating an artillery strike east of Tây Ninh found 17 PAVN/VC dead. At 14:50 a unit of the 3rd Brigade, 1st Cavalry Division engaged an enemy force northwest of Phước Bình supported by artillery, helicopter gunships and AC-47 and AC-119 gunships. The enemy withdrew at 19:00, leaving 17 dead; U.S. losses were four killed, including Second Lieutenant Robert Ronald Leisy, who shielded a fellow soldier from the blast of a Rocket-propelled grenade (RPG), an action for which he was posthumously awarded the Medal of Honor. At 19:15 a unit of the 2nd Brigade, 25th Infantry Division patrolling northeast of Go Dau Ha engaged an enemy unit in a 25-minute firefight. The enemy withdrew, leaving nine dead and six AK-47s.
On 3 December in the early morning there were attacks by fire on Dầu Tiếng Base Camp, Tây Ninh Combat Base and Quản Lợi Base Camp causing minimal damage. At 14:45 a unit of the 3rd Brigade, 1st Cavalry Division, engaged an enemy force southwest of Bù Đốp, killing five and capturing two AK-47s. At 18:20 helicopter gunships from the 1st Squadron, 9th Cavalry Regiment (1/9th Cavalry) attacked an enemy force northwest of Phước Bình, killing 22. At 18:25 a light observation helicopter from the 3rd Brigade, 9th Infantry Division, received fire east-southeast of Tân An, Brigade infantry moved to the area and killed five PAVN/VC in a brief skirmish. An OH-6 Cayuse light observation helicopter was shot down northwest of Mộc Hóa District.
On 4 December in the early morning, there were attacks by fire on Tây Ninh Combat Base and Sông Bé Base Camp causing minimal damage, at Sông Bé helicopter gunships of the 2nd Brigade, 1st Cavalry Division, attacked the firing positions causing two secondary explosions. At 13:00 a unit of the 1st Brigade, 25th Infantry Division, was air-assaulted into the location of an airstrike west of Tây Ninh where they found ten PAVN/VC dead and three SKS rifles and base camp with a 4-ton rice cache and seventy-three 60 mm mortar rounds. On 5 December, in the early morning, an attack by fire hit Tây Ninh Combat Base, causing minimal damage. At 00:30 helicopter gunships from the 1st Cavalry Division received fire northeast of Tây Ninh and attacked the firing position, 15 PAVN/VC dead were seen in the area. At 11:00 a unit of the 3rd Brigade, 1st Cavalry Division, engaged an enemy force west of Phước Bình, the enemy withdrew after 30 minutes, leaving seven dead; U.S. losses were two killed. Also at 11:00 a unit of the 199th Light Infantry Brigade (199th LIB) engaged an enemy platoon southeast of Biên Hòa, the enemy withdrew after 30 minutes with unknown losses; U.S. losses were two killed. At 16:30 the 1/9th Cavalry supported by artillery and helicopter gunships engaged an enemy unit northeast of Tây Ninh, the enemy withdrew at 19:00, leaving 20 dead.
On 6 December, in the early morning, Quản Lợi Base Camp was attacked by fire causing minimal damage. At 09:15 a unit of the 1st Brigade, 1st Cavalry Division and Civilian Irregular Defense Group program (CIDG) troops engaged an enemy force northeast of Tây Ninh supported by artillery, helicopter gunships and airstrikes. The enemy withdrew after 20 minutes, leaving 45 dead and 12 individual weapons, one 60 mm mortar and a 12.7mm machine gun. At 11:00 south of the earlier contact another unit of the 1st Brigade engaged an enemy force, the action continued until 16:00 when the enemy withdrew, leaving eight dead and seven individual weapons; U.S. losses were one killed. At 13:00 a unit of the 199th LIB operating northwest of Xuân Lộc District found the bodies of ten PAVN/VC killed earlier by airstrikes.
On 7 December at 01:50, a UH-1 Iroquois from the 1st Cavalry Division received fire north of Tây Ninh, the helicopter engaged the enemy and called in artillery and airstrikes and ten PAVN/VC dead were seen in the strike area. At 12:10 a unit from the 3rd Brigade, 1st Cavalry Division, was attacked northeast of Lộc Ninh District, the unit returned fire and the enemy withdrew immediately, leaving five dead, one individual weapon and one RPG launcher; U.S. losses were one killed. At 15:25 a unit of the 1st Brigade, 1st Cavalry Division, engaged 25–30 PAVN/VC southeast of Katum Camp supported by artillery, helicopter gunships and airstrikes. The enemy withdrew at 15:40, leaving 19 dead and one .30 cal machine gun. At 15:45 helicopters from the 1/9th Cavalry attacked an enemy force northeast of Bù Đốp, killing nine. At 17:15 1/9th Cavalry helicopters received 12.7mm fire from the same area and attacked the position, killing 13 PAVN/VC. At 17:30 a unit of the 3rd Brigade, 1st Cavalry Division, was attacked west-northwest of Phước Bình, the unit returned fire supported by artillery and airstrikes and the enemy withdrew after 20 minutes, leaving six dead and one individual weapon. At 17:40 a unit of the 3rd Brigade, 1st Cavalry Division, engaged an enemy force southwest of Bù Đốp; the enemy withdrew after 45 minutes with unknown losses; U.S. losses were one killed.
On 8 December in the early morning attacks by fire were made on most base camps in the operational area causing minimal damage. At 08:20 a unit of the 1st Brigade, 1st Cavalry Division, engaged an enemy force southeast of Katum, the enemy withdrew after two hours, leaving 23 dead and three crew-served weapons. At 18:20 helicopter gunships from the 1/9th Cavalry attacked an enemy force north of Tây Ninh, killing ten. On 9 December at 09:10, a unit of the 3rd Brigade, 1st Cavalry Division, engaged an enemy squad northwest of Phước Bình, the enemy withdrew at 15:00, leaving eight dead; U.S. losses were one killed. At 09:40 a unit of the 3rd Brigade, 1st Cavalry Division, patrolling west-northwest of Phước Bình engaged an enemy force, the enemy withdrew after 30 minutes, leaving 13 dead. At 13:00 a unit of the armored cavalry squadron of the 25th Infantry Division was attacked 8 miles northeast of Trảng Bàng District, the unit returned fire supported by artillery, helicopter gunships and airstrikes. The enemy withdrew at 18:00, leaving 13 dead. At 16:00 Rangers and a reconnaissance unit of the 199th LIB found a weapons cache northeast of Xuân Lộc containing 12 RPG-7 launchers, 40 RPG-2 grenades and 136 82 mm mortar rounds.
On 10 December at 00:15, a unit of the 1st Brigade, 25th Infantry Division, observed enemy forces near their night defensive position northwest of Tây Ninh and engaged them with small arms and artillery fire. A sweep of the area at dawn found six PAVN/VC dead, three RPG launchers, two AK-47s and a radio. At 13:10 a unit of the 3rd Brigade, 1st Cavalry Division, engaged an enemy squad northeast of Lộc Ninh, the enemy withdrew after 30 minutes, leaving two dead. At the same time northwest of Phước Bình a unit of the 3rd Brigade, 1st Cavalry Division, found 11 PAVN/VC dead and five individual and one crew-served weapons, all had been killed by artillery fire in the previous 12 hours. At 17:25 helicopter gunships from the 1/9th Cavalry attacked six PAVN/VC northeast of Bù Đốp, killing all six. At 19:30 a unit of the 2nd Brigade, 25th Infantry Division, was attacked southwest of Lai Khê, the unit returned fire supported by artillery and helicopter gunships and the enemy withdrew after an hour, leaving six dead.
On 11 December at 00:05, a unit of the 3rd Brigade, 25th Infantry Division, was attacked north of Hiệp Hòa, the unit returned fire supported by artillery and helicopter gunships and the enemy withdrew. At 10:30 a unit of the 1st Cavalry Division engaged an enemy force northeast of Phước Bình, killing 36. At 13:10 a unit of the 1st Brigade, 1st Cavalry Division, found nine PAVN/VC dead northeast of Tây Ninh all had been killed by airstrikes. At 15:30 an armored unit of the 25th Infantry Division found 16 PAVN/VC dead northeast of Tây Ninh all had been killed by small arms and airstrikes in the previous two days. At 16:00 a unit of the 199th LIB engaged an enemy force southeast of Biên Hòa, the enemy withdrew after 20 minutes, leaving three dead; U.S. losses were one killed. At 21:10 helicopter gunships of the 1st Cavalry Division received fire northeast of Phước Bình and engaged the firing position supported by artillery, 11 PAVN/VC dead were seen in the strike area.
On 12 December between 01:50 and 03:10 helicopter gunships of the 1st Cavalry Division received fire northeast of Phước Bình and attacked the firing position supported by an AC-47 gunship and 11 PAVN/VC dead were seen in the strike area. At 02:00 helicopter gunships of the 1st Cavalry Division attacked an enemy force southeast of Katum, killing five. At 07:45 a Ranger unit from the 3rd Brigade, 9th Infantry Division, engaged an enemy force south-southeast of Tân An. The unit was supported by artillery and helicopter gunships and the fighting continued until 18:05 when the enemy withdrew, leaving 20 dead and one captured and five individual weapons; U.S. losses were on killed. At 15:05 a unit of the 3rd Brigade, 1st Infantry Division operating 10 miles west of Chơn Thành District engaged an enemy force. The enemy withdrew at 17:45, leaving eight dead and three individual weapons. At 15:10 a unit of the 3rd Brigade, 25th Infantry Division, was air-assaulted into an area northwest of Hiệp Hòa and were immediately engaged by an enemy force. The unit returned fire supported by artillery and helicopter gunships and the enemy withdrew at 20:30, leaving five dead and one individual and one crew-served weapon; U.S. losses were one killed. At 16:00 helicopter gunships from the 1/9th Cavalry received fire northeast of Phước Bình and attacked the firing position supported by artillery fire, killing 11 PAVN/VC. At 17:55 helicopter gunships of the 1/9th Cavalry killed five PAVN/VC east of Phước Bình. At 19:10 a unit of the 3rd Brigade patrolling 4 miles north of Hiệp Hòa was attacked, the unit returned fire and the enemy withdrew after two hours; U.S. losses were one killed. At 20:00 another Brigade patrol was attacked in the same area, the unit returned fire supported by artillery and helicopter gunships and the enemy withdrew after 45 minutes; U.S. losses were four killed.