History of Riverine Forces in the Vietnam War
- Feb 27
- 16 min read
Updated: 2 days ago
A short history of the Riverine Forces in the Vietnam War
A brown water navy or riverine force, refers to maritime forces specific to operations within inland waterways, including rivers, lakes, and coastal areas. The term originated during the U.S. Civil War, when it was used to describe Union naval vessels patrolling the Mississippi River. Today, it broadly encompasses small patrol boats and gunboats deployed in coastal areas and on rivers, supported by larger motherships. While riverine units remain an element of the modern U.S. Navy, the phrase "brown-water navy" is most associated with its significant operational role in the Vietnam War, securing the Mekong Delta.
The Mekong River originates in the mountains of Tibet and flows about 2,600 miles before reaching the South China Sea. Its course traverses multiple Southeast Asian countries, including Myanmar (formerly Burma), Laos, and Cambodia, ultimately spreads into a sprawling delta in southern Vietnam. The Mekong Delta constitutes roughly one-fifth of the former South Vietnam’s land area, which is comparable in size to the state of West Virginia. This substantial region primarily comprises plains and fields divided by an intricate network of rivers and canals. During the wet season, from June to October, flooding is common; for example, the Plain of Reeds—a major rice-producing area in the northern portion of the Delta—can experience floodwaters up to ten feet deep. Conversely, the dry season, from November to April, results in dry fields and low water levels in the canal systems.
A substantial portion of Vietnam’s rice production occurs within the Delta, more than 16 million tons per year. So you could call it the “rice bowl” of the country. Unimpeded access to more than 15,000 miles of waterways plays a critical role in trade, transportation, and fishing. These characteristics underscore the strategic significance of the Mekong Delta in southern Vietnam, necessitating tough security measures, which led to the deployment of U.S. Riverine Forces.
The region was designated as the IV Corps Tactical Zone during the Vietnam War. The North Vietnamese Army didn’t operate in the area, but the Viet Cong did. They controlled about a quarter of the population in the Delta. There were approximately 70,000 VC fighters in the zone and another 11,000 political cadre running a shadow government in the region. The Viet Cong were highly motivated, well trained and equipped with a variety of small arms. Their basic weapons were the AK-47 and the Rocket Propelled Grenade (RPG). The RPG was a boat killer, but the AK-47 fired a 7.62mm round capable of piercing the hull of an unarmored patrol craft.
The VC benefited from their familiarity with the local people, terrain, and waterways. They mostly relied on sampans, which are traditional flat-bottomed wooden boats common in Southeast Asia, often disguising themselves as merchants or fishermen. Civilians contributed to smuggling supplies for the VC, either willingly or under duress. Because of the terrain, heavy weapons had to be moved by hand or transported in sampans, making it difficult for the VC to assemble large forces or launch significant operations in the Delta. As a result, most battles were small, fast, and fought at close range, typically between 20 and 200 feet apart.
The Mekong Delta had limited roads, and numerous bridges were destroyed by the VC, making river and canal security vital for civilians and commerce. It was also crucial to prevent enemy use of these waterways. To accomplish this mission before U.S. involvement, three divisions of the Army of the Republic of Vietnam (ARVN), supported by five ranger battalions and various local forces, operated in the IV Corps Tactical Zone. To transport these troops throughout the Delta, South Vietnamese forces fielded 13 river assault groups, each with 20 boats—most of which were repurposed from the earlier conflict with the French.
U.S. advisors began working with the South Vietnamese Navy in 1957, but American combat units weren’t deployed to the Delta until Viet Cong advances made U.S. support necessary. In 1965, the U.S. Army’s 13th Combat Aviation Battalion arrived with four helicopter assault companies and one reconnaissance airplane company. By mid-1966, U.S. naval forces, including Task Force 115, code named Operation MARKET TIME and Task Force 116, Operation GAME WARDEN, were committed. MARKET TIME had the mission of patrolling coastal areas to prevent resupply of enemy forces by sea. GAME WARDEN had the assignment of interdicting enemy movement of troops and supplies in Delta waterways and assisting government forces in repelling enemy attacks.
The third organization of the Brown Water Navy was TF 117, also known as the Mobile Riverine Force (MRF), was created in late 1966. This unit was the assault force of the joint Army-Navy campaign in the Delta. One might think that the Mobile Riverine Force’s ground combat element would have been a natural mission for the Marine Corps, but all Marine assets in South Vietnam were deployed in the I Corps Tactical Zone, fighting near the DMZ. The Mobile Riverine Force ground combat mission was given to the 2nd Brigade of the U.S. Army’s 9th Infantry Division.
The River Patrol Force, Task Force 116 - The Gamewardens
The River Patrol Force, otherwise known as TF 116 or the Gamewardens for the operation name, were assigned the new Patrol Boat, River or PBR Mk1. You might recognize the PBR from the movie “Apocalypse Now.” It was a high-speed, shallow-draft, diesel-powered, freshwater patrol craft with a fiberglass hull and water jet propulsion. The PBR was the first jet-propelled watercraft used in combat. Built by United Boat Builders of Bellingham, Washington, the first boats were delivered in March 1966. The water jet propulsion was a significant feature of the PBR. The boat was propelled by jetting pressurized water through nozzles in the stern. No rudder or propellers, steering was accomplished by changing the nozzle direction. This allowed the boat to make high speed turns, (360 degrees at 25 knots in just 110 feet) and operate in just a foot of water.
The PBR Mk1 measured 31 feet long and 10 feet 7 inches wide, reaching speeds of up to 25 knots. It was armed with twin forward .50-caliber machine guns, an aft .50-caliber, and a 40mm Mk 18 grenade launcher amidships. Its electronics included depth gauges, radios, and radar with a two to three thousand yard range. A four-person crew—boat captain, engine man, gunner’s mate, and seaman—operated the weapons and systems.
Some issues with the Mk1 quickly became apparent, like vegetation sometimes clogging the water jet pumps, and the forward gun shield restricting visibility of the coxswain. 161 Mk1s were modified to correct these issues. Development of the Mk2 variant took place in 1966. The first PBR Mk2s were deployed in Vietnam in September 1967. Eighty-one Mk2s were delivered through 1968. Over the course of the War, about 300 PBRs would see combat.
Task Force 116's main goal was to patrol and secure South Vietnam's waterways. This meant the Game Wardens were charged with stopping Viet Cong infiltration in the Mekong Delta. In February 1966, the Navy clarified that Task Force 116 aimed to prevent VC troops and supplies from moving along inland water routes, disrupt enemy lines of communication, enforce nighttime curfews, and protect Saigon's main shipping channels through regular patrols and minesweeping operations. Game Wardens conducted operations throughout the Delta region, extending from river mouths up the Mekong River to the Cambodian border. In addition to permanent bases, Game Wardens received logistical support from larger vessels, often modified Landing Ship, Tank (LST) types, which served as mobile bases. These support ships relocated daily to reduce vulnerability to Viet Cong mortar attacks. Game Warden Patrol Boat, River (PBR) units typically deployed in pairs for patrols lasting 12 to 14 hours.
The Game Wardens received support from two, occasionally three, SEAL Team 1 platoons; Helicopter Attack Squadron 3, known as the Seawolves, which operated 25 UH-1B gunships; and Light Attack Squadron 4 with fifteen OV-10A Bronco fixed wing observation and attack aircraft. Additional units included Mine Division 112, equipped with twelve minesweeping vessels; Patrol Air Cushion Vehicle Division 107, utilizing three PACVs; and Strike Assault Boat Squadron 20, which provided 22 Strike Assault Boats in support of the SEALs. The Strike Assault Boat, often referred to as the "SEAL Team Assault Boat," was a 26-foot aluminum vessel engineered for high speed and primarily used for SEAL insertion and extraction missions. In 1970, the Task Force had a fluctuating strength of approximately 2,000 personnel operating a total of 258 craft.
Task Force 115 - Operation MARKET TIME
Task Force 115, executing Operation Market Time, sought to establish an effective coastal surveillance capability. This required a vessel that was faster and better equipped for open ocean operations than the PBR. The North Vietnamese were engaged in large-scale movement of supplies by water into South Vietnam. Identification was challenging amid the 64,000 licensed vessels—including junks, sampans, and fishing boats—operating in the Delta region. While most supplies and personnel from North Vietnam arrived via the Ho Chi Minh trail, a considerable volume was transported by sea. Maritime delivery offered greater efficiency and direct access to units along the coast compared to long overland routes. To counter this supply chain, Task Force 115 was provided with Patrol Craft, Fast, commonly referred to as Swift Boats, which were designed specifically to enhance interdiction efforts.
Swift Boats were an all-aluminum, 50-feet long boat designed to handle the open ocean. Prop driven, its top speed was 32 knots and had a draft of only 3 feet 10 inches. Bigger than the PBR, the Swift Boat had a pilothouse and deckhouse. Armament was similar with a twin 50-caliber machine gun mounted on the pilothouse. On the fantail was a single 50-caliber machine gun and an 81mm mortar capable of both indirect and direct fire. The crew of five consisted of the boat captain, usually a lieutenant or lieutenant junior grade, a coxswain, a radar or radioman, gunner’s mate, engineman and seaman. The Navy bought 193 Swift Boats, most of which served in Vietnam.
TF 115 was activated in July 1965, structuring Coastal Squadron 1's Swift Boats into six divisions tasked with patrolling 1,200 miles of coastline. Each division consisted of 16 to 22 boats, with crews operating on 24-hour rotational patrols. Coastal Squadron 1 operated alongside Coast Guard Squadron 1, which included 28 cutters, and Patrol Squadron 3, comprising five patrol gunboats, under the coordination of Coastal Flotilla 1—a unit that expanded to 1,050 personnel by 1968. The task force was also responsible for harbor defense operations at Vung Tau, Cam Ranh Bay, Qui Nhon, and Nha Trang. Operation Market Time achieved a reduction in enemy boat infiltration by at least percent.
Swift Boats participated in river patrols alongside River Patrol Force PBR's and the Mobile Riverine Force. The Patrol Craft, Fast was originally designed for inshore or coastal operations to prevent enemy infiltration of supplies. Subsequently, Swift Boats were assigned to operations within interior waterways as part of the brown-water navy’s efforts to intercept Vietcong movement, transport South Vietnamese forces, and deploy SEAL teams for counterinsurgency missions. Their design, especially their wide turning radius, made the Swift Boat less suitable for these tasks. Additionally, the lack of armor protection posed challenges during close-range engagements in the delta. Moreover, the vessels were not structurally equipped to withstand the rigors of riverine operations.
The Mobile Riverine Force was established as a joint Army-Navy force to conduct offensive operations in the Delta. Considered the most viable method of regaining the initiative from the VC, the Mobile Riverine Force would take advantage of the region’s natural means of communication, movement on the water. The Navy component of the MRF was River Assault Flotilla One, aka Task Force 117, commissioned in September 1966 at Naval Amphibious Base Coronado (San Diego). After assembling boat crews, Flotilla staff, and a period of training, the advance elements arrived in Vietnam in early January 1967.
In the spring, a base was constructed in Dong Tam to support the Mobile Riverine Force's Army component, specifically the 2nd Brigade of the 9th Infantry Division. This facility was situated three miles west of My Tho, along the Song My Tho (river), approximately twenty miles southwest of Saigon. However, due to limited available land, heightened security requirements, and local resistance to the presence of American troops—which risked escalation—the principal operating base for the Mobile Riverine Force was established afloat. The floating base not only minimized interaction with the local population but also provided flexibility to relocate operations as needed, enhancing the mobility of the force beyond its boat-borne combat units. River Support Squadron 7 managed the mobile riverine base, utilizing barracks ships, repair ships, and salvage craft.
The Mobile Riverine Force's naval combat units were organized into River Assault Squadrons 9 and 11. Each squadron was split into two divisions, with each division able to transport and support an infantry battalion. These units also had attachments such as an Underwater Demolition Team (UDT), an explosive ordnance disposal detachment, and a riverine survey team. Initially, the plan was for floating barracks to operate upriver, but concerns over their vulnerability to swimmer attacks, stand-off assaults, and their deep draught preventing travel further up river, led to a change. Instead, the barracks were stationed seaward of the river mouth, serving as bases for the River Assault Squadron units.
Initially, the newly formed unit received borrowed vessels that were made in the United States but operated by Vietnamese crews. These simple Landing Craft, Mechanized (LCM) with modifications, lacked sufficient armament and armor, yet provided valuable training for the American crew members. The first elements of the 9th Infantry Division arrived and began their training in mid-January 1967, with more Vietnamese craft lent to support the process. By March, new American vessels started arriving.
Task Force 117 - the Mobile Riverine Force (MRF)
In 1968, TF 117 expanded with two new River Assault Squadrons, two more Assault Support Patrol Boats, a barracks ship, and an LST. The Navy had 3,700 personnel in TF 117 that year. Troops navigated the Delta using mission-specific boats like Assault Support Patrol Boats, Armored Troop Carriers, and Monitors (also called “Mike Boats”).
The Assault Support Patrol Boat served a variety of roles, including river patrols, escort missions, providing fire support, and minesweeping. These vessels were heavily armed and armored, and they could travel at speeds up to 16 knots with a shallow draft of three feet. Measuring 50 feet in length and weighing 29 tons, the first boats arrived in Vietnam in September 1967. Soldiers and sailors nicknamed them “Alpha Boats” because of the ‘A’ prefix in their hull numbers. Each boat had a crew of six who operated a twin 50-caliber machine gun mounted on a forward turret, a 20 mm cannon positioned atop the deckhouse, and an 81 mm mortar located at the rear.
The Alpha boats were designed to serve as escorts for Armored Troop Carriers, offering equivalent armor protection while aiming for faster speed and maneuverability compared to the vessels they accompanied. However, the incorporation of heavy armor and certain design elements intended to enhance survivability ultimately resulted in diminished maneuverability relative to PBRs. Consequently, Alpha boats were not necessarily favored by their crews.
Existing Landing Craft, Mechanized (LCM), were adapted to serve as Armored Troop Carriers for the Mobile Riverine Force. These vessels measured 56 feet in length and 17 feet in width, drawing only three and a half feet of water. While the original ramp was designed for vehicle offloading, its primary function in riverine operations was to transport either a platoon of soldiers or up to 12 tons of cargo. The Armored Troop Carrier, designated as the “Tango Boat” due to the letter prefixing its hull number, reached a maximum speed of eight and a half knots, typically operating at a cruising speed of six knots.
The Tango Boats featured robust construction, including a double steel hull and armored protection for both weapons turrets and the wheelhouse. Each Armored Troop Carrier had a crew of seven, equipped with two .50 caliber machine guns mounted in side turrets directly aft of the wheelhouse, a 20 mm cannon in an aft turret, four 7.62 mm machine guns, and two 40 mm grenade launchers along the gunwales. Subsequent design enhancements included upgrading the .50 caliber machine guns in the side turrets to 20 mm cannons, further increasing the vessel's firepower.
The initial generation of Armored Troop Carriers featured a removable helicopter landing platform installed above the troop compartment. One or two vessels in each River Assault Squadron served as medical aid boats. Casualties were transferred to these aid boats, where medical staff onboard provided stabilization prior to the arrival of a medevac helicopter, which landed on platforms sized specifically for Huey helicopters. Approximately seventy-five percent of Tango boats were equipped with armored landing platforms that also functioned as overhead protection for the troop compartment.
Under Project Douche, two Tango Boats were equipped with powerful water cannons for firefighting. Each "Douche boat" had two cannons shooting a stream of water at 3,000 pounds per square inch, fed by centrifugal pumps and able to deliver 1,000 gallons per minute per cannon. Although their maximum range was 300 yards, they were mostly used at close distances to clear shoreline bunkers, remove vegetation, and flood spider holes. The cannons could also assist in extinguishing fires on other boats.
Certain Tango Boats were designated to carry 81mm mortars, serve as artillery fire direction centers, or transport ammunition and supplies. Their duties included patrolling, blocking escape routes, and safeguarding floating howitzer batteries. With Assault Support Patrol Boats arriving later, some of these tasks were shifted away from the Tango Boats. Watercraft from the Mobile Riverine Force aided ground troops by transporting soldiers and acting as—or supporting—a blocking force. They handled reconnaissance, security operations, and combat patrols, moved crew-served weapons, and carried out resupply and evacuation missions.
Significant modifications to the Armored Troop Carrier resulted in the creation of the Monitor. Commonly referred to as a “Mike Boat,” Monitors served as the “battleships” of the Mobile Riverine Force. The original bow ramp was removed and replaced by a rounded, barge-style bow featuring a forecastle deck that covered most of the well deck. A portion of the well deck remained open to accommodate a direct fire mortar. The forward turret was equipped with a coaxial 50-caliber machine gun alongside a 40mm grenade launcher, while 20mm cannons were installed in the side and aft turrets.
Subsequent updates enhanced the capabilities of these vessels. One notable modification involved removing the 81mm mortar, covering the well, and installing a 105mm M49 howitzer turret further aft. Another variant, referred to as the "flamethrower boat" or "Zippo," also featured the removal of the direct fire mortar and decking over the well. In its place, two M10-8 flame guns housed in M8 cupolas were positioned aft of the 40mm gun. A total of eight "Zippo Boats" were deployed during the Vietnam war.
Command and Control boats, also known as “Charlie Boats,” were modified versions of the Monitor. Their well deck was transformed into a Tactical Operations Center (TOC) that featured a steel-sided, peaked vinyl-canvas cover. Inside the TOC, there was space for three extra radios, an encryption device, worktables, and map boards. Typically, four Army personnel from battalion headquarters staffed the TOC, including a staff officer, an artillery officer, and two enlisted soldiers. The 81 mm mortar and gunwale machine guns were removed, but otherwise the Charlie Boats carried the same weaponry as a Mike Boat.
The ground component of the Mobile Riverine Force was established with the arrival of the 2nd Brigade of the 9th Infantry Division in Vietnam in December 1966. This brigade comprised three infantry battalions, each structured with a headquarters company, a combat support company, and three rifle companies. Unnecessary vehicles and equipment were stored at Dong Tam. To enhance operational effectiveness, some of the battalion’s support personnel were reassigned to form two additional rifle platoons, which, together with the battalion’s existing scout platoon, created a fourth company. This arrangement ensured that one company could provide base security while the remaining three rifle companies were available for deployment in field operations.
While riverine craft transported and aided ground troops, those soldiers spent a lot of time as passengers. If they were ambushed, they'd fire back using their own weapons and prepare to put ashore and leave the boats. When the riverine force encountered a hostile engagement, it might fight through the attack and carry on with its original mission, as ambushes often served to delay progress. Sometimes, a few troops would deploy on shore to engage and pursue the attackers directly, or units could land on the flanks to try to trap the enemy. Additionally, a quick reaction force delivered by helicopter might be deployed to intercept the retreating ambushers.
The ground force generally deployed to locations where intelligence had identified enemy presence. Operations involved sweeping the area, frequently supported by blocking forces positioned via parallel streams or helicopter insertion. If no enemy activity was discovered during the sweep, combat patrols were conducted and ambushes established at night along trails and waterways. The ground force could be withdrawn on the same day of insertion or remain for periods extending up to three days. Extended deployments often led to immersion foot issues. To mitigate this, one of the battalions would stay at the floating base to recover while operational rotations continued.
Under President Nixon’s Vietnamization program, the U.S. military began a systematic reduction of their forces, transferring combat responsibilities to the Vietnamese armed forces. Assets such as Mobile Riverine Force boats were transferred to the Vietnamese Navy, and two river assault squadrons were decommissioned in June 1969. In the same month, the 9th Infantry Division received notification of its withdrawal, with the 2nd Brigade departing first at the end of July 1969.
Operation SEALORDS
Operation SEALORDS (Southeast Asia Lake, Ocean, River and Delta Strategy), a collaborative initiative between American and South Vietnamese forces, had been established at the end of 1968. Beginning in early 1970, the coastal, river, and river assault task forces were unified under Task Force 194 as part of SEALORDS, resulting in a consolidated brown water fleet, leveraging the strengths of the former three task forces. Increasingly, operational resources and responsibilities transitioned to the South Vietnamese, whose sailors underwent training and integration with U.S. crews. Operational control was gradually assumed by the South Vietnamese command. By 1971, all facets of Operation SEALORDS had been transferred to the South Vietnamese Navy, and the U.S. naval presence was reduced to a 500-man Naval Advisory Group. Following the signing of the Paris Peace Accords in January 1973, all of the remaining American military personnel departed Vietnam by March 1973.
Books by Jim Travis Broumley
The Boldest Plan is the Best
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The Bridge at El Djem
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The Avellino Jump
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AnzioAnzio Italy, 1944 - 1LT Jack Bell and his fellow paratroopers prepare to make a beach landing in Italy. The problem is that the civilians in Naples know where they’re going before they do. Along with everything else, Jack is put in the position of escorting OSS officer Boyd Carter on a raid of a German held blockhouse to “capture” an old friend. Now Carter is wounded and Jack is a prisoner. Can Jack’s friends and their green platoon leader mount an unauthorized rescue?
Operation DragoonCpt Jack Bell and the rest of the 509th PIB jumped into Southern France as part of Operation Dragoon. Before the battalion can move out to attack the Germans in Le Muy, Maj Boyd Carter shows up with a mission for Jack. Rescue an Air Corps major, nine miles behind the lines and hidden by a group of French Resistance fighters. The Geronimos are outnumbered, but "Rube" Roubideaux has a plan to even the odds.
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