The II 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 it oversaw the Central Highlands region, north of the capital Saigon. Its corps headquarters was in the mountain town of Pleiku.
History 1957-1963 II Corps headquarters became operational in October 1957 and was responsible for the Central Highlands and the coastal region from southern Quang Nam province south to the town of Phan Thiet. II Corps headquarters was originally located at Ban Me Thuot in the Central Highlands, but was moved to Pleiku in mid-1959. Its assigned units were the 12th Light Division at Kontum, the 14th Light Division at Qui Nhon, the 15th Light Division at Duc My, the 3rd Field Division at Song Mao, and miscellaneous units stationed in the region. US advisors at II Corps headquarters consisted of about a dozen officers and enlisted men with a colonel of infantry as senior corps adviser, and two lieutenant colonels to advise the corps engineer, armor, ordnance, and Signal units.
1964 Following the 1963 South Vietnamese coup d'état, coup leader General Dương Văn Minh reassigned II Corps commander General Nguyễn Khánh to command I Corps, allegedly to get him as far from Saigon as possible. On 30 January 1964 Khánh overthrew Minh in a bloodless coup. By 6 March Khánh had replaced three of the four Corps commanders.
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.
The Diem regime's relative success in pacifying significant parts of I and II Corps had led to decisions in 1963 and 1964 to transfer troops to more troubled areas further south. This meant that troops were leaving just as the VC were increasing their efforts. Northern II Corps, like southern I Corps, was a long-standing revolutionary bastion and the VC had made deep penetrations in the last two months of 1963 following Diem's ouster.
In May 1964 the North Vietnamese politburo established three subordinate commands, including the Western Subregion, renamed the B–3 Front in September 1964, it encompassed the provinces of Kontum, Pleiku, and Darlac. The politburo envisioned it would be the decisive battle theater, where the Communists could best trap and destroy major government units before pushing down from the mountains and into the populated plains.
South Vietnam considered the Central Highlands of strategic importance too. The ARVN had considerable resources at their disposal and believed they outnumbered the VC by 4.6 to 1, but given the Corps' size, they had to spread their troops thinly. Corps commander General Đỗ Cao Trí positioned the 25th Division on the northern coast, the 22nd Division in the west, and the 23rd Division in the south. Corps' plans for 1964 were to focus initially on pacifying the densely populated north-south corridor that bordered Highway 1 and the railway, as well as communities along the zone’s three important east-west routes that connected the coast to the highlands, Highways 19, 20, and 21. Once Tri had secured the major communication axes, he planned to target the gaps between pacified areas, first on the coast and then in the piedmont. The Civil Guard would bear most of the population security burden at close-in communities, whereas the ARVN would perform operations on the fringes of populated areas, with occasional raids into the mountainous interior.
In late April 1964 II Corps launched Operation Quyet Thang 202, a successful assault on the VC's Do Xa stronghold that straddled Quang Ngai, Quang Tin, and Kontum provinces on the northern border of II Corps.
The VC summer offensive commenced in July 1964, lessened in August and then peaked in September. By summer’s end, advisers reported modest progress in pacification in five of the Corps' 11 provinces, however it had deteriorated significantly in four provinces — Pleiku, Quang Ngai, Binh Dinh, and Phu Yen.
On 19 September Montagnard irregulars in the Central Highlands mutinied, seizing several outposts and killing 73 people. The rebellion ended on 28 September when the rebels laid down their arms in exchange for amnesty and promises of future concessions.
Also in September the 25th Division began moving to III Corps' Hau Nghia Province to support Hop Tac pacification operations, leaving behind one of its regiments in Quang Ngai. Efforts to backfill the hole created in Quang Ngai by the division's transfer floundered, thereby contributing to the serious losses in population control that were already underway in that forlorn province. In hindsight, MACV commander General William 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 Joint General Staff reassigned Lam Dong, Binh Thuan, and Binh Tuy provinces from III Corps to II Corps.
In late 1964, as monsoon flooding destabilized the countryside, small bands of VC continued to infiltrate into the lowlands to support local cadre in wresting control over rural communities. As in I Corps, Khanh's decision to funnel all recruits to III and IV Corps exacerbated the situation, undermining both morale and fighting strength. By October, II Corps had only 86% of its authorized manpower. Service and support units were near capacity, but combat units were at 46% strength. The Corps' Ranger battalions were particularly undermanned, leading Westmoreland to make a special appeal on their behalf. The loss of the 25th Division and the net gain of two additional provinces because of the corps boundary shifts worsened the situation further.
In October, the Corps' new commander, Major general Nguyễn Hữu Có, increased the number of battalions assigned to pacification duty from eight to ten, a considerable effort considering that he had just lost the 25th Division. Area control by saturation patrolling was the modus operandi for these units. During the month, nine of his provinces reported slight pacification gains and four—Binh Dinh, Phu Yen, Pleiku and Darlac—reported regression. However, the deterioration in security became so widespread through the Corps' northern tier that Có felt compelled to respond. He cut the number of battalions directly supporting pacification from ten to four. He then used the manpower freed from pacification duty to launch offensive operations that he hoped would drive the enemy's larger units out of populated areas, thus gaining some breathing room. Monsoon damage and increased VC attacks impacted Binh Dinh province severely.
Westmoreland blamed himself for the deterioration that had occurred in the northern and central coastal provinces. At his urging, the South Vietnamese had dispersed much of their forces to support pacification, only to be overrun by main force enemy units. Population control was assessed to have declined from 76% in January to 51% 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. 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 January 1965 was relatively quiet in II Corps. Có took advantage of the respite to double the number of battalions assigned to province chiefs for pacification from nine to 18, while launching 30 operations involving a battalion or more.
By the end of the Tết holiday in early February, Military Region 5 and the B–3 Front were ready to launch a new surge in the winter-spring offensive. Their goal was to carve up South Vietnam into several isolated blocks. Northern II Corps would once again be the focal point of this effort. First, the VC wanted to cut South Vietnam in two by controlling a stretch of land from the Cambodian border to the sea that ran through Kontum, Pleiku, and Binh Dinh provinces in II Corps and Quang Ngai province in I Corps. Second, they planned to isolate the western highlands from the populated eastern lowlands by interdicting Highway 19.
The VC began its new wave of attacks in the early hours of 7 February. The first targets were transportation facilities such as roads, railroads, airfields, and fuel depots. The VC damaged or destroyed 15 railroad bridges in northern II Corps and I Corps. In Phu Yen, they attacked Chop Chai airfield and destroyed 331 barrels of fuel at Tuy Hoa. With these actions, the VC hoped to impede the allies' ability to respond to the coming offensive in the north. The Attack on Camp Holloway killed seven Americans, destroyed ten helicopters and damaged 15 more. On 10 February a VC sapper attack in Qui Nhon killed 21 US soldiers and 11 South Vietnamese civilians.
On 16 February a US Medevac helicopter discovered a heavily-armed trawler in Vũng Rô Bay near Tuy Hoa. The discovery showed that the North Vietnamese were using coastal infiltration to resupply the VC.
From 20 to 24 February Có launched an operation to reopen Highway 19 which had been closed by the VC since 30 January. The PAVN/VC defeated the ARVN forces and Highway 19 wouldn't be reopened until mid-March.
Binh Dinh remained the focus of the VC offensive. Since 7 February, the VC had captured 131 hamlets in the province, and the population had lost faith in the government’s ability to protect it. Thousands of refugees fled the VC in northern Binh Dinh, leaving them in near total control. In MACV's opinion, government control in Binh Dinh had dwindled to 21% of the population and 10% of the land.
On 8 March the VC launched an unsuccessful attack on the Kannak CIDG camp on Highway 19, losing 131 dead and 65 weapons. The CIDG troops lost 33 dead and three US Army Special Forces soldiers were killed. On 9 March a VC attack on Ha Tay resulted in more than 200 VC killed, while an attempt to seize and hold Hoai An town was defeated. These attacks marked the crescendo of the VC offensive.
On 26 March the 21st Ranger Battalion engaged an enemy force west of Highway 14 near the Laotian border. The five-day skirmish killed 82 PAVN/VC for the loss of 24 Rangers killed and seven missing. The action confirmed that the PAVN 101st Regiment was now fighting in South Vietnam.
By the end of March, the immediate threat of the VC splitting South Vietnam had passed, but the price had been high. In addition to the casualties suffered, the winter- spring offensive had forced Có to divert troops from pacification. He had reduced the number of regulars assigned to province chiefs from 18 battalions in January to ten in February and to zero in March. The move weakened the already hard-pressed pacification effort. By the end of March, the government admitted the presence of more