BiA ArmA 3 Campaign - Rung Sat Special Zone

published on: 15/03/2026

Author: W. Jarvis

Historical background of the Rung Sat Special Zone

On the 8th of June 1962, following years of growing Viet Cong activity around the Capital city of Saigon, the South Vietnamese Government authorised the creation of the Rung Sat Special Zone. This area would cover a large area of the Sác forest, today known as the Cần Giờ Mangrove forest, with Saigon to its northwest and the South China Sea to its southeast. The name ‘Rung Sat’ means ‘assassins forest’ and received its name after the bandits that used to occupy the area, stopping commercial boats and robbing the passengers. Much of the Sác forest can be described as a mangrove swamp, with a vast network of small rivers and canals running through the area. American intelligence estimated that 60 per cent of the economic and logistical support received from the United States was still being brought into South Vietnam through the Lòng Tàu River, making the area critical to the South Vietnamese economy.

Due to the dense nature of the forests within the zone making ground operations difficult for South Vietnamese forces, the Viet Cong were able to establish base areas and gradually build forces from the late 1950s. The expansion of the Viet Cong presence within the area greatly concerned the South Vietnamese government as attacks against commercial shipping on the Lòng Tàu River, the only navigable deep-water channel leading to Saigon, mounted over time. Following these attacks, the Vietnamese Navy, officially the Republic of Vietnam Navy, was assigned control over the area while being assisted by a team of American advisors under the command of the U. S. Naval Advisory Group Chief in Saigon. Furthermore, in order to combat the growing Viet Cong presence, from 1965 the USAF began defoliating (clearing the trees and other vegetation within an area with chemical agents) the zone as part of Operation Ranch Hand. In April of 1966, the area was designated as the D-10 Special Military Zone by the Central Office for South Vietnam, the American name for the North Vietnamese headquarters within South Vietnam.

By early 1966, the Viet Cong had established a sizable presence within the Rung Sat Special Zone, the dense forests allowed the VC to transport men, ammunition and medical supplies into the province to mount raids on commercial shipping en route to Saigon. In February, the Viet Cong ambushed the Panamanian flagged freighter ‘SS Lorinda’, wounding six of the crew and causing the ship to run aground, prompting Military Assistance Command, Vietnam (MACV) to conclude that a large-scale, American led, amphibious raid into the zone would be necessary to ease VC pressure on the shipping channel. This raid, dubbed Operation Jackstay, would be assigned to the USMC 1st Battalion, 5th Marines, supported by the 4th and 5th RVN Marine Corps Battalions.

Operation Jackstay saw four assault landings by boats and four by helicopter undertaken by American forces, and two assault landings by Vietnamese Marines, one by boat and one by helicopter, from March 26th through the 6th of April. The operation was highly successful, not only because 62 Viet Cong soldiers were killed by American forces, who only suffered 5 casualties, but also due to the large number of weapons, grenades and ammunition captured. The Post Operation Report (NIS 4/21/66) for Operation Jackstay claimed that American forces had seized or destroyed 24 small arms weapons, 2 arms factories, 200 land mines and over 60,000 rounds of ammunition, with medical supplies, clothing, and manufacturing equipment also seized by American and South Vietnamese forces.

Following the conclusion of Operation Jackstay in March of 1966, the USMC would hand control of the Rung Sat Special Zone over to the US Army’s 18th Infantry Regiment, followed by responsibility passing to the 9th Infantry Division and the newly established Mobile Riverine Force who carried out patrols along the canals and small rivers of the zone. In order to protect ships en route to Saigon, the U.S. Navy established Mine Squadron 11, Detachment Alpha (later renamed Mine Division 112) equipped with twelve 57-foot fiberglass-hulled MSBs, which continuously swept the river for VC activity to ensure the safety of merchant ships.

Despite the efforts of the South Vietnamese government, with the support of American forces, Viet Cong activity continued to grow through 1966-1967. It is notable that from December 1965 to February 1967 the Viet Cong made 18 separate attacks against commercial shipping vessels traversing the Lòng Tàu River, the most well known being the attack on the SS Baton Rouge Victory by Viet Cong placed naval mines in August of 1966. Allied naval losses continued to mount through this time, with a Vietnamese Navy minesweeper sunk in August 1966 by VC fire, killing or wounding seven of its crew. In January of 1967, another Vietnamese Navy minesweeper was sunk during an ambush. On the 15th of February U.S. Navy MSB-49 was struck by a recoilless rifle and sank soon after, wounding all six crew members, followed by the loss of MSB-45, which resulted in the deaths of two sailors and wounded 16 others. By the end of 1967, a further six merchant ships were attacked by the Viet Cong.

The 1968 Tet Offensive launched by People's Army of Vietnam regulars and the Viet Cong across the entirety of South Vietnam saw one of the most active periods of fighting within the Rung Sat Special Zone. Attacks against shipping increased drastically during this time, with a total of 44 separate incidents involving VC forces firing on commercial vessels. In April, two sailors were killed when the tug ‘Michael’ was struck by VC fire, and in August the cargo ship ‘Transglobe’ was hit by a 122mm rocket, killing one crewmember. However, the intensity of the fighting gradually weaned off towards the end of the year as a result of the heavy casualties in both men and material suffered by the Viet Cong during the Tet Offensive. The surprise and severity of the Tet Offensive, however, did result in an ever growing number of Americans to believe that a victory in Vietnam was unattainable, with President Richard Nixon, newly elected in November 1968, announcing his plan to gradually withdraw American forces from Vietnam.

Moving into 1969, after the Viet Cong had spent some months replenishing its strength in the Rung Sat, attacks against shipping once more grew exponentially. In the first half of 1969 alone, the VC launched some 51 assaults on commercial vessels with small arms fire, mortars and occasionally with the several recoilless rifles that had been smuggled into the area under the cover of the thick foliage of the Sác forest. This spike in Viet Cong activity once more prompted Military Assistance Command, Vietnam (MACV) to plan an operation within the zone to target VC camps, ammunition dumps and seize the weapons being used to attack shipping.

This operation (possibly a part of the numerous operations undertaken under the ongoing Tiger Coronado or Coronado campaigns, although no official name for this operation could be found) was mounted in June by a joint force from the Mobile Riverine Force, Republic of Vietnam Navy, and American, Australian and Thái infantry units. Exact details on the events of this operation are unknown but it is claimed that the operation was successful, resulting in the destruction of four Viet Cong base camps and the death or capture of at least 53 VC fighters. Followup clearing operations saw army bulldozers and aerial-sprayed herbicides used to denude the dense foliage of the Sác forest. Following the conclusion of this operation, South Vietnamese and American forces continued to apply pressure onto the scattered Viet Cong, frustrating their efforts to regroup.

The impact of this operation was immediate, with attacks on shipping dropping rapidly through to the second half of 1969. Furthermore, the VC didn’t launch a single attack against merchant vessels until well into 1970, however, in November Viet Cong forces did attack the cargo ship ‘President Coolidge’. As the Viet Cong focused its attention on other sectors, particularly on attacking critical infrastructure like the Bien Hoa Air Base, the number of attacks again dropped through the end of 1970, it wasn’t until the next year that another vessel was struck by VC fire, the merchant ship ‘Raphael Semmes’.

During this period of relative calm within the Rung Sat Special Zone, the responsibility of performing anti guerilla operations was handed over to the 1st Australian Task Force (1 ATF) following the 9th Infantry Division departing from the theater and the Mobile Riverine Force being disbanded. Australian forces, namely the 8th Battalion of the Royal Australian Regiment, mounted Operation Cung Chung II and III which aimed to maintain control over South Vietnamese population centres through the region with mixed results. From July to November of 1970 1 ATF mounted 17 boat patrols within the Rung Sat with limited results, before switching to helicopter patrols that would land troops to investigate reports of Viet Cong activity.

With the number of allied personnel deployed to the Rung Sat continuing to reduce as American and Australian forces gradually departed from South Vietnam the Viet Cong were able to once more consolidate their positions within the area. The next major action saw the People's Army of Vietnam once again attempt to invade South Vietnam conventionally as part of the failed 1972 spring-summer offensive. By this time the Viet Cong based around Saigon had switched much of its attention from the allied shipping on the Lòng Tàu River to the National Highway Route 1, another key logistical route for the South Vietnamese war effort, as well as shelling Saigon itself with mortars and rockets.

Following the withdrawal of American combat forces with the signing of the Paris Peace Accords in January of 1973 the Viet Cong once again stepped up attacks on both on the Lòng Tàu River and the National Highway Route 1, gradually increasing the pressure on the Capital of Saigon. Despite the signing of a supposed peace agreement, its provisions were immediately broken by both North and South Vietnamese forces with open fighting across South Vietnam once again breaking out in March of 1973. The People's Army of Vietnam were able to launch several offensives that enlarged their territory by the year's end without the interference of the United States. Over the next year, the Republic of Vietnam continued to lose territory throughout the country to joint PAVN / VC offensives, culminating in the 1975 Spring Offensive, resulting in the collapse of South Vietnamese forces in the Central Highlands in March and the fall of Saigon in April, effectively conquering the country. The two nations would once again unite as the Socialist Republic of Vietnam in 1976.

To conclude, the Rung Sat Special Zone was a key theatre of operations for the South Vietnamese government, Military Assistance Command, Vietnam (MACV) and the Central Office for South Vietnam (or Viet Cong). For the Viet Cong, due to much of the merchant shipping destined for Saigon travelling through the Lòng Tàu River they were able to concentrate their efforts on one goal, impeding traffic along the river, the terrain certainly helped with this, the dense nature of the Sác forest allowed the VC to build up their forces and effectively hide right under the noses of allied forces, however, the Americans and South Vietnamese didn’t allow the VC to operate with impunity. U.S. forces launched multiple large scale and effective raids into the Rung Sat throughout the war, most notable being Operation Jackstay in 1966 and the joint U.S., Australian and Thái operation in 1969, which successfully reduced the activity of Viet Cong units surrounding Saigon. Furthermore, operations mounted by the Mobile Riverine Force and Mine Division 112 were able to effectively provide commercial vessels with protection as they traversed the river. By 1970, thanks in part to the continual pressure applied against the VC through a combination of air strikes, river patrols and search and destroy missions the Viet Cong had lost much of the men and equipment they had brought into the zone, however, the American and Australian withdrawal from Vietnam had left Saigon vulnerable once more, allowing the Viet Cong, supported by the People's Army of Vietnam to achieve its ultimate goal of unifying Vietnam in 1976.