In the Battle of Binh Gia from 28 December 1964 to 1 January 1965 the division lost 32 killed for Army of the Republic of Vietnam losses of 201 killed. In the Battle of Ba Gia from 28 to 31 May 1965, the division destroyed an ARVN task force and claimed to have killed or wounded 915 ARVN and captured 270, while the ARVN claim to have killed 566 PAVN. In the Battle of Đồng Xoài from June 9 to 13 1965, the division overran the CIDG camp at Đồng Xoài and then ambushed the relief forces killing 416 ARVN and at least 20 US while losing 126 killed. According to the official history of the PAVN, the division was only formed on 2 September 1965 from the 1st Regiment, the 2nd Regiment and the newly formed 3rd Regiment drawn from local forces in the Mekong Delta. The division was engaged in the Battle of Ap Bau Bang on 12 November 1965, losing 146 killed and 50 probably killed for US losses of 20 killed. In Operation Mastiff from 21 to 25 February 1966, the US 1st Infantry Division engaged elements of the division in the Dầu Tiếng District killing 61 for the loss of 17 US. In Operation Cocoa Beach from 3 to 8 March 1966, the division's 272nd Regiment was engaged by the 3rd Brigade, 1st Infantry Division on Highway 13 near Lai Khê, losing 199 killed for US losses of 15 killed. In Operation Birmingham from 24 April to 17 May 1966, US/ARVN forces engaged elements of the division in Tây Ninh Province killing over 100. In Operation El Paso from 19 May to 13 July 1966, US and ARVN forces engaged the division in Bình Long Province killing 825 with a further 1,249 estimated killed for the loss of 125 US killed. The Division was the target of Operation Junction City from 22 February to 14 May 1967, with the division losing 2,728 killed, 34 captured and 139 deserters. During the operation in the Battle of Prek Klok II the division's 272nd Regiment lost 197 killed and 5 captured. In the Second battle of Bàu Bàng from 19 to 20 March 1967, 2 battalions of the division lost 277 killed and 3 capture for 3 US killed. In the Battle of Suoi Tre on 21 March 1967 the 272nd Regiment lost 647 killed and 7 captured for US losses of 36 killed. In the Battle of Ap Gu from 31 March to 1 April the 271st Regiment lost 609 killed and 5 captured for US losses of 17 killed. In Operation Billings from 12 to 26 June 1967, the division's 271st Regiment was engaged by the US 1st Infantry Division north of Phước Vĩnh losing 347 killed for US losses of 57 killed. In Operation Shenandoah II from 29 September to 10 December 1967, the US 1st Infantry Division and ARVN forces engaged the division along Highway 13. Within this operation in the Battle of Ong Thanh on 17 October 1967 the Division's 271st Regiment ambushed the US 2nd Battalion, 28th Infantry Regiment killing 68 Americans for the loss of 22 killed. In the First Battle of Loc Ninh 29 October - 7 November 1967 the Division attacked Lộc Ninh losing 852 killed while killing 50 US/ARVN. In Operation Yellowstone from 8 December 1967 to 24 February 1968, the division was engaged by the US 25th Infantry Division. In an attack on Firebase Burt on the night of 31 December 1967, the 271st and 272nd Regiments lost 379 killed and 8 captured for U.S. losses of 23 dead. Elements of the division's 273rd Regiment were engaged by Australian/US forces during Operation Coburg from 24 January to 1 March 1968. During the Tet Offensive the division's 271st and 272nd Regiments unsuccessfully attempted to interdict roads around Củ Chi Base Camp to prevent movement by US forces. The 273rd Regiment was supposed to attack the town of Thủ Đức but was detected and engaged in the village of An My losing 343 killed. One battalion of the 273rd Regiment escaped Any My and suffered almost 400 killed in the fighting at Thủ Đức. The division also unsuccessfully attacked Tan Son Nhut Air Base on 31 January-1 February 1968 losing more than 669 killed and 26 captured, while killing 22 US and 29 ARVN. During Operation Quyet Thang from 15 to 17 March 1968, the US 3rd Squadron, 11th Armored Cavalry Regiment and ARVN forces engaged the 272nd Regiment between Đức Hòa and Củ Chi, killing 273. During the Phase III Offensive on 18 August 1968, a battalion from the 273rd Regiment, 9th Division, unsuccessfully attacked Firebase Buell II losing 104 dead and 8 captured. The same night division sappers attacked the US base on Nui Ba Den killing 8 US for the loss of 15 sappers killed. During Operation Chenla II from 20 August to 3 December 1971, the division defeated units of the Khmer National Armed Forces who attacked their base areas in eastern Cambodia. The entire division was involved in the Battle of An Lộc from 13 April to 20 July 1972. As a result of his failure to seize the town quickly, the commander of the 9th Division was officially reprimanded and local command was handed over the senior officer of the PAVN 5th Division. In the Battle of Hồng Ngự from March to 4 May 1973, the division's 272nd Regiment and 2 Regiments from the 6th Division lost 422 killed in their unsuccessful attempt to capture the town of Hồng Ngự. ARVN losses were 94 killed and 36 missing. A battalion of the division's 271st Regiment took part in the initial phases of the Battle of Tong Le Chon until replaced by a battalion of the 201st Independent Regiment. In the Battle of the Iron Triangle from 16 May to 20 November 1974, the division's 95C Regiment suffering heavy losses in the fighting at An Dien in May/June. From 24 to 31 March 1975 the Division made repeated attacks on Chơn Thành Camp losing at least 18 tanks and 340 killed before the defending 31st Ranger Group successfully evacuated the camp on the night of 31 March/1 April.
