The NVA in South Vietnam
The People’s Army of Vietnam (PAVN) was known to the American forces as the North Vietnamese Army (NVA) also divided North Vietnam and South Vietnam into military regions; similar to the Tactical Zones defined by the United States. The NVA had four Military Regions (1-4) in North Vietnam, and, around 1964-1965, established numbers for regions in South Vietnam.
Military Region 5 covered the northern half of South Vietnam (the US/ARVN I CTZ and II CTZ south to Dar Lac and Khanh Hoa provinces). The 1st, 2nd and 3rd VC Regiments were all active in this region; the 1st was engaged in Quang Ngai Province during August, 1965. In fall 1965 it reorganized its forces into the 2nd and 3rd Divisions and 10th Regiment. MR 5 consisted of the lowlands from Da Nang to Nha Trang and was the B-1 Front or B-1 Theater.
The Tay Nguyen Front (also known as the B-3 Front or B-3 Theater)was subordinate to MR 5, and established September, 1964. It covered the central highlands parallel to the Ho Chi Minh trail. (It also roughly corresponded to part of the VC’s MR 10 and part of MR 1 regions.)
The Tri-Thien-Hue Military Region was establishedt in April, 1966 in the Quang Tri and Thua Thien provinces. It was in control of the B-4 Front and the B-5 Front (established June, 1966); the latter along Route 9 and the former the rest of the area. These two fronts were separate until March, 1972. The B-5 initially operated under the control of Military Region 4, the southernmost region in North Vietnam. The B-4 and B-5 Fronts were combined in November, 1972.
The 70 (70B) Corps was established October, 1970 to coordinate the 304th, 308th, and 320th NVA Divisions and various other units along Route 9 and in Laos. It was still active iin the Quang Tri area in March, 1972.
The Southern Regional Headquarters controlled the B-2 Theater; Military Regions 6 to 9 and the Saigon-Gia Dinh Special Zone. Military Region 6 covered the rest of ARVN’s II CTZ and the very northern part of III CTZ. The westernmost elements MR 6 and MR 7 basically fell into the VC’s Region 10. Military Region 7 (Eastern Nam Bo Region) covered the ARVN’s III CTZ, down to the Saigon area. In October, 1967, this region took over the Saigon-Gia Dinh Special Zone; which was pretty much the VC’s regions 1 and 4. Military Region 8 was southwest of Saigon, running from Cambodia to the South China Sea; largely the VC’s Region 2. Military Region 9 covered the southernmost part of South Vietnam; largely the VC’s MR 3.
These Military Regions were roughly intact from 1965 until around somewhere in 1973-1975. 1st Military Corps established in the north October 24th, 1973 (Divisions 308, 312, 320B; AA Division 367; Artillery Brigade 45; Tank Brigade 202; Engineer Brigade 299), and moved to the south late March, 1975 for the final push on Saigon.
2nd Military Corps established May 17th, 1974 in Tri Thien Front (Divisions 304, 324, 325; AA Division 367; Tank Brigade 203; Artillery Brigade 164, Engineer Brigade 219). Following the collapse of the ARVN in I CTZ in 1975 it pushed elements down the coast.
3rd Military Corps established March 26th, 1975 utilizing the command staff of the Tay Nguyen Front (Divisions 10, 316, 320; Artillery Regiments 40 and 675; AA Regiments 234 and 593; Tank Regiment 273; Engineer Regiment 7). It controlled the push on Saigon through eastern South Vietnam in the final offensive.
4th Military Corps established July 20th, 1974 (Divisions 5, 7, 9; Artillery Regiment 24; AA Regiment 71; Engineer Regiment 25; Sapper Regiment 429). This led the attack on Saigon from the northwest; shifting Division 5 and gaining Division 341. This corps grew out of Group 301, established March 18th, 1971 (Divisions 5, 7 and 9 and Artillery Regiment 28) to control forces operating against the ARVN invasion of Cambodia that year..