III Corps () was a corps of the Army of the Republic of Vietnam (ARVN), the army of the nation state of South Vietnam that existed from 1955 to 1975. It was one of four corps in the ARVN, and oversaw the region of the country surrounding the capital Saigon.
History 1959-1963 III Corps headquarters was activated in September 1959 at Bien Hoa and controlled the country south of Phan Thiet, excluding Saigon which was controlled by the Capital Military District (CMD). Its assigned units being the 11th and 13th Light Divisions at Tay Ninh and the 4th Field Division at Bien Hoa.
In 1962, President Ngô Đình Diệm decided to split the Corps into two, the former III Corps area being reduced in size to cover the area northeast of Saigon and the newly created IV Corps taking over the west and southwest.
The 5th Division based in Bien Hoa on the northern outskirts of Saigon was a part of III Corps, and due to the division's close proximity to the capital was a key factor in the success or failure of the various coup attempts in the nation's history.
Following the 1963 South Vietnamese coup d'état, the junta had appointed General Tôn Thất Đính to command III Corps. In January 1964, the junta changed its mind and replaced Đính with General Trần Thiện Khiêm.
In December 1963, with the Corps' leadership in a state of flux, the senior U.S. military advisor, Colonel Wilbur Wilson took the initiative to draft goals for the coming year. "Close coordination between military and civil administrators must be emphasized," he wrote, to bring 95% of the Corps' population under control by the end of 1964. Not only did he want to see more hamlets built, but he also sought to improve existing hamlets by introducing better-trained officials and significant socioeconomic programs. Militarily, his first priority was to improve the militia and the Self-Defense Corps. With these forces more able to secure their communities, the Civil Guard and the army would be able to engage in offensive combat. Wilson wanted infantry units maintained at 90% strength and kept in the field 20 days per month. He believed small-unit operations, backed by robust programs of civic, psychological, and intelligence action, held the key to success.
1964 On 30 January 1964 General Nguyễn Khánh overthrew General Dương Văn Minh in a bloodless coup. By 6 March Khánh had replaced three of the four Corps commanders. Khánh appointed Brigadier general Lâm Văn Phát as the new III Corps commander. A March 1964 assessment by Wilson, described Phát as a "personally very charming" former French officer who spoke excellent English. "As a matter of protocol will almost always agree with a recommendation on most any subject, but this does not mean that the recommendation will be implemented." Politically ambitious but "professionally incompetent and emotionally unstable," Phát was known to "lash out with his swagger stick and give... a caning on the spot" to any soldier who displeased him. Yet at the same time, he exhibited what Wilson termed "almost a psychopathic horror of issuing a direct order to a subordinate." In April, Khánh replaced Phát with Brigadier general Trần Ngọc Tám.
On 24 February 1964 Khánh issued the 1964 National Campaign Plan under the name Chien Thang (Struggle for Victory). Khanh decided the provinces surrounding Saigon would receive top priority in the distribution of troops, civil servants, and money. The rest of III Corps and IV Corps were next in the resource queue, whereas the provinces of II and I Corps had the lowest priority. One reason why the north received the least resources was that, at least before late 1963, it had appeared to be in the best shape. Thus, Chien Thang forecast that I and II Corps would be the first to enter into the final phase, the destruction of the enemy's last major formations and bases in January 1965, whereas III and IV Corps would not reach that point until January 1966.
To implement pacification in its most important areas, III Corps organized 700 civilian cadre in 35 groups of 20 men each. Each group consisted of a command element, a police team, a militia training team, a psychological warfare team, and a health team. The plan envisioned that the groups would follow on the heels of military forces as they cleared territory. Their mission was to separate the people from VC operatives and to establish control. Once done, they would gradually transfer authority to normal civil government. Reflecting government priorities, III Corps assigned the groups to Hau Nghia, Gia Dinh, Binh Duong, Tay Ninh, Long An, Bien Hoa, and Dinh Tuong provinces, as well as the newly created province of Go Cong.
Assisting III Corps, Wilson had under his operational control several hundred advisers, the 145th Aviation Battalion and the Utility Tactical Transport Company, redesignated as the 68th Aviation Company in March 1964.
Opposing the allies was a robust VC force consisting of two regimental headquarters, nine battalions, plus many smaller units for a total of 18,000 regulars, a figure nearly equal to the number of VC regulars in the rest of South Vietnam. After considering the enemy’s irregulars, MACV estimated that the government outnumbered the VC by just 2:1 in III Corps. Binh Duong and Hau Nghia provinces were VC strongholds, Phuoc Thanh province hosted War Zone D, while Tay Ninh province, hosted COSVN headquarters and War Zone C in the north.
The high command subdivided III Corps into nine military commands. Initially, six of these reported to the III Corps commander, one reported to his naval aide, and two reported directly to the Joint General Staff (JGS). The official reason for the division of authority was to address local circumstances better and to avoid overburdening the Corps' commander and his two division commanders. MACV came to see the multiplicity of commands as a weakness, as the commands did not have the staff required to operate effectively.
In early 1964 the Vietnamese agreed to test a new system for handling immediate requests for aviation assistance from US and Republic of Vietnam Air Forces operating in the Corps. MACV stationed air liaison officers, forward air controllers, and radio operators at each special zone, regiment, and division headquarters, as well as at the headquarters for the Corps and the airborne brigade. Initially, the new system consisted entirely of USAF people, with the plan to transition eventually to an all-Vietnamese system once enough personnel were available. MACV envisioned that the system would fast-track impromptu requests for air support, bypassing province chiefs and intermediary commanders.
On 8 June 1964 Corps' commander Tam told his subordinate commanders that the government was losing the war. Over the past two months, the ARVN had lost 489 dead in III Corps compared to 328 dead insurgents, and he believed the vc exaggerated their losses. He blamed the officer corps' lack of aggressiveness, knowledge, and leadership for the situation.
In July the VC launched their summer offensive with a series of attacks on isolated outposts and then ambushing the relief forces. Activity subsided in August and then surged again in September.
On 1 September the Hop Tac pacification program was launched in the Corps' provinces immediately surrounding Saigon - Gia Dinh, Bien Hoa, Binh Duong, Hau Nghia, Long An, and Phuoc Tuy.
On 5 September, the JGS abolished the Tien Giang Tactical Area. It transferred the 7th Division and four of the five provinces it supervised to IV Corps and assigned Long An Province to III Corps.
Also in September the 25th Division began moving from II Corps to Hau Nghia province to support Hop Tac pacification operations, leaving behind one of its regiments in Quang Ngai. The JGS then assigned one of the independent regiments already stationed in III Corps to the 25th Division to build the organization back up to its full complement. As predicted, desertions grew and morale sank because of the move. In MACV commander General William Westmoreland's opinion, it took about three years for the 25th Division to regain its efficiency. Westmoreland believed it would have been better to have left the 25th Division in Quang Ngai and to have organized an entirely new division for service in III Corps. In addition, the JGS abolished the Binh Lam Special Zone in III Corps and divvied up its provinces. Long Khanh now fell under the Phuoc Bien Special Zone, and Lam Dong, Binh Thuan, and Binh Tuy provinces were reassigned from III Corps to II Corps.
In mid-October Major general Cao Văn Viên replaced Tam as the Corps' commander.
For their winter-spring offensive in III Corps, COSVN planned a major campaign for late December 1964. Instead of targeting the western part of the Corps, which had been the site of most of the major battles of 1964, it chose the relatively quiet east. After preliminary attacks on Bình Giã in early December, the VC launched a full-scale attack on 28 December and in a battle that lasted until 1 January 1965 they achieved a significant victory over several units of elite South Vietnamese forces.
During 1964 population control was assessed to have increased from 45% in January to 49% in December.
By the end of 1964 a US Army helicopter aviation company or US Marine Corps helicopter squadron was assigned in direct support of each Vietnamese infantry division, with two additional helicopter companies in general support of III and IV Corps. Further fixed-wing transport, reconnaissance, and observation aircraft were available as well. As a result, each senior Corps adviser had between 70 and 100 aircraft at his disposal, with MACV retaining control over the rest.
1965 Following their victory at Bình Giã, COSVN recalled its two main force regiments to base areas to rest and refit. It completed the formation of new units of regulars and sought to secure further its supply lines from Cambodia and between War Zones C and D. Lastly, COSVN developed Plan X, a scheme for what it hoped would be a general uprising in and around Saigon. Plan X gave the Saigon-Gia Dinh Military Region the task of creating a commando unit large enough to capture key targets in Saigon in one swift, decapitating blow. Supplementing the commandos would be armed teams based in every sector of the city. They would lead the city's residents to action on the appointed day. The Saigon-Gia Dinh Military Region was also to raise five spearhead battalions that would converge quickly on the city to reinforce the commandos and armed teams until COSVN’s main force regiments arrived from outside the region. Preparations began in January with the formation of a new mobile regiment and the Group 165A Training Center in Tay Ninh province.
MACV's priority in III Corps was to advance pacification, particularly in the Hop Tac region. With more than two dozen battalions routinely assigned to Hop Tac security and 78% of the Corps' regular army units assigned to pacification and security missions, the number of forces left in the Corps for offensive actions was limited. Security was particularly tenuous in Phuoc Tuy and Phuoc Long, in part because the Saigon government had failed to respond to requests to raise more Regional Forces in these two provinces. Throughout the Corps, the VC weakened the public's confidence by occasionally bombarding key towns with mortars.
In early March the VC began a new terrorist bombing campaign in Saigon. On 4 March, a bomb exploded outside a Saigon bar, killing four children. A week later, a mine destroyed a bus in Long An province, killing 13 civilians. On 30 March, a car bomb detonated outside the US embassy, killing two Americans and 20 Vietnamese.