1957-1961 IV Corps headquarters was located at
Mỹ Tho with its assigned unit being the 16th Light Division. The
7th Division based in Mỹ Tho, and due to the division's close proximity to the capital
Saigon was a key factor in the success or failure of the various coup attempts in the nation's history. In the
coup attempt of 1960, the loyalist Colonel
Huỳnh Văn Cao used the 7th Division to storm into Saigon to save President
Ngô Đình Diệm.
1962 In 1962, Diem decided to split the command of the area in the south around Saigon 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. Cao was promoted to general and assumed command of the new IV Corps Tactical Zone, which included the area of operations of his 7th Infantry Division. On 15 April the
United States Marine Corps began
Operation Shufly to improve the mobility of ARVN forces by deploying a Marine helicopter squadron to
Soc Trang Airfield. On 24 April 16 USMC helicopters supported the 21st Division in Operation Nightingale conducted near Can Tho. The operation resulted in 70 VC killed and three captured for the loss of three ARVN killed. Khánh replaced General
Nguyễn Hữu Có with a political supporter, Brigadier general
Dương Văn Đức as Corps' commander. On 18 December the US Navy established
Operation Game Warden to interdict VC infiltration in the Mekong Delta. Task Force 116 was the main unit responsible for Game Warden and it consisted of five divisions patrolling different sections of the Delta, originally equipped with
river patrol boats (PBRs) and
mine sweeping boats (MSBs). In the Combined Campaign Plan for 1966, which the JGS and MACV issued in December, the allies declared their "basic objective" for the year to be clearing, securing, and developing the heavily populated regions around Saigon, in the Mekong Delta, and in selected portions of the I and II Corps coastal plain. "Coincident" with this effort, they would defend significant outlying government and population centers and conduct search and destroy operations against "major VC/PAVN forces." In pursuit of these objectives, South Vietnamese forces would concentrate on defending, clearing, and securing the designated strategic areas. American and third-country forces, besides securing their own bases and helping to protect rice-producing areas, were to "conduct operations outside of the secure areas against VC forces and bases." Implicit in these words was the defacto division of labor between the South Vietnamese and Americans that had been in effect since the summer.
1966 In November the Directory appointed General
Nguyễn Văn Mạnh to replace Quang as Corps' commander. The heavily populated central Delta, composed of An Giang, Sa Dec, and Vinh Long provinces as well as portions of Phong Dinh and Vinh Binh was the Corps' National Priority Area. Mạnh's task was to maintain and expand government control and to keep the overland link with Saigon, Highway 4, free of VC harassment. About two-thirds of his combat strength at anyone time was devoted to offensive operations, while the remainder handled pacification security. However, Mạnh was unable to take the initiative from the VC and by 1967 the best Saigon could claim in the delta was a stalemate. By November 1967, MACV analysts determined that roughly a third of the people who lived in the 16 delta provinces that made up the Corps Tactical Zone lived under some degree of VC control. VC main and local forces the IV Corps numbered 22 battalions and 74 companies. Backing them were an additional 32,000 guerrilla and infrastructure personnel. COSVN controlled those forces through two regional headquarters. Military Region 2 encompassed the provinces in the upper part of the Corps, an area more or less bounded by the Bassac River to the south and the Vam Co Tay River to the north. Its headquarters was in Base Area 704 on the border of Kien Tuong province and Cambodia. The second command, Military Region 3, directed operations in the Corps’ southern and western provinces. It resided in the U Minh Forest on the southwestern coast of Kien Giang province. From July to October the 44th Special Tactical Zone, whose principal forces consisted of the 7th Ranger Group and the 4th Armor Group, conducted operations to force the PAVN 1st Division out of the Seven Mountains region, a chain of rugged, forested, cave-pocked peaks stretching 25km in a ragged line from the Cambodian border at
Tịnh Biên to below
Tri Tôn. By October the 1st Division had been deactivated and its units incorporated into the 101D Brigade.
1974 From 12 February to 4 May in the
Battle of Tri Phap, Corps' forces successfully launched a pre-emptive attack on a PAVN base area in Dinh Tuong province. On 9 March the PAVN fired an 82 mm mortar shell into the
primary schoolyard at Cai Lậy while the children were lined up waiting to enter their classes. Twenty-three children died instantly; 46 others were badly wounded. On 30 October Thieu replaced Nghi as Corps' commander with Major general
Nguyễn Khoa Nam. From 6-26 December PAVN/VC forces in the Delta had conducted the most widespread and intense attacks thus far in the war. They struck with greatest force in the Elephant's Foot area of Kien Tuong province, but strong attacks also occurred along lines of communication in Dinh Tuong, Chuong Thien, Da Xuyen, Vinh Binh, Vinh Long, and An Xuyen Provinces. Casualties on both sides were heavy: the ARVN had over 500 killed in action, and total casualties, including wounded and missing, exceeded 3,000; PAVN/VC casualties were estimated at over 3,500.
1975 During January violence spread throughout the Delta in a pre-Tết spasm of PAVN/VC attacks on lines of communication, cities, villages and outposts. General Nam continued to reduce the number of indefensible, isolated posts and to consolidate combat power in larger positions. Sixty-three posts in the delta were abandoned under this plan in January, while another 87 were either overrun or evacuated under pressure. Of the latter, ARVN counterattacks regained 24. The heaviest losses were in the far south, in Bac Lieu, where 23 posts were lost and only four retaken, and in An Xuyen, where 16 posts fell and only two were recovered. Half the posts voluntarily abandoned were also located in these two provinces, while the central provinces of Phong Dien and Sa Dec and the northern border sector of Kien Phong suffered very light damage. Even in the key central province of Chuong Thien, the ARVN lost very little; of the six posts lost to enemy attack, four were recaptured. In northern Kien Tuong Province along the Cambodian-Svay Rieng border the PAVN 5th Division and the 7th Division engaged in heavy combat. By the end of January only two ARVN positions remained in Tuyen Binh District.
Long Khot outpost was overrun by elements of the PAVN 6th and 174th Regiments using captured M113 armored personnel carriers. Toward the end of February, the 5th Division withdrew the battered 6th Regiment from action and sent it into Cambodia to receive replacements. In mid-February the collapse of FANK forces in Cambodia caused more than 7,000 people, including at least 500 military, to seek refuge in Chau Doc province. ==Divisions==