By 1966 US troops had been committed in large numbers to three of the four corps areas of Vietnam. Only in IV Corps, the Mekong Delta region, were there no large numbers of American troops. This was due to three major factors. First, though the delta was a major population and food center, the military situation was not as critical as in the other corps areas. Second, due to the density of the population, there was no available tracts of land where a large military installation could be constructed without dislocating large numbers of people. And finally, the numerous rivers, streams and canals which dissected the delta severely restricted ground movement; US planners were reluctant to commit US troops to such an environment until they found a way to overcome the mobility problem.

However, in 1966, there was a strong desire on the part of the US Army to insert troops in the Mekong Delta to counter growing communist strength. In March of 1966 a joint planning committee of Army and Navy personnel drew up tentative plans for the establishment of a Mekong Delta Mobile Afloat Force (MDMAF). This proposal was further detailed during the summer, and by September plans had reached the implementation stage, On 1 September, the first administrative unit of the new organization was commissioned at the Navy Amphibious Base in Coronado, California. Shortly after this, the unit received the designation Task Force 117 (TF-117), and was code names the Mobile Riverine Force. (MRF).

As originally envisioned the MRF would support an infantry brigade and an artillery battalion using a variety of modified landing craft, support ships, and specially designed assault boats. In essence this strike unit would be, a self contained amphibious assault force, complete with all support elements except aircraft. The ideal choice for the ground component would have been the Marines who were specialists in amphibious warfare, but unfortunately the Leathernecks were already heavily committed in I Corps. Instead, a brigade from the 9th Infantry Division was chosen as the infantry component of the Mobile Riverine Force.

The Naval component of TF-117 was made up of a wide variety of ships and boats. The first unit, River Assault Squadron 9 (RAS 9), consisted of four APB’s, two LST’s, twenty-six ATCs, five Monitors, two CCBs, one Refueler, and sixteen ASPBs.

River Assault Flotilla One

Task Force 117

River Assault Squadron 9
Task Group 117.1

River Assault Squadron 11
Task Group 117.2

River Assault
Division 91

13 ATC
3 Monitor
1 CCB
8 ASPB

EOD Team

River Assault
Division 91

13 ATC
2 Monitor
1 CCB
8 ASPB
1 Refueler

River Assault
Division 111

13 ATC
3 Monitor
1 CCB
8 ASPB

EOD Team

River Assault
Division 112

13 ATC
2 Monitor
1 CCB
8 ASPB
1 Refueler

RIVER SUPPORT SQUADRON 7
Task Group 117.3

BENEWAH (APB 35), COLLETON (APB 36), APL 26,
ASKARI (ARL 30), SUPPORT LST (1156 Class), YTB’s 784,785
Support and Salvage Craft as Assigned

The small craft were equally divided between River Assault Divisions 91 and 92 (RAD 91 and RAD 92) while the support ships formed River Support Squadron 7 (RSS 7). Eventually another six divisions would be added to TF 117. Except for the ASPB which was newly designed, All these Craft were basically standard navy vessels modified for use with the MRF.

The first elements of the Mobile Riverine Force reached Vietnam on 7 January 1967 when the USS Whitfield County (LST 1169) docked at Vung Tau. Training began immediately with the 2nd Brigade of the 9th Infantry Division. This unit, in preparation for the assignment to the Mobile Riverine Force, had gotten rid of their tanks, trucks, APCs and jeeps since there would obviously be little need for them in the Mekong Delta. In addition, some of their heavier artillery was also left behind since most of the necessary fire support would be supplied by the assault boats. Unfortunately, because the initial number of barracks ships could only handle two of the brigade’s three infantry battalions and artillery batteries, the remaining units had to operate out of the newly constructed shore facility at Dong Tam until the rest of TF-117’s ships were available.

The major problem initially faced by the MRF was the lack of having their own vessels to train on. For the fist few months TF-117 used borrowed Vietnamese Navy landing craft and control boats until its own boats began arriving. During this time, the Viet Cong carried out a number of attacks against ships on the Long Tau River. On 15 February 1967 the VC sank one US minesweeper and damaged three others. As a result of these attacks, plans were made to carry out regular search and destroy missions in the Rung Sat zone which bordered the Long Tau, even though the Mobile Riverine Force lacked their own boats. Working with Vietnamese units operations were carried out through March which resulted in a substantial drop in the attacks by the communist guerrillas. However despite these efforts the Rung Sat continued to be used by the VC and throughout the war allied forces had to periodically sweep the area to deny the enemy free access to it.

Gradually the MRF built up its strength. However, the number of boats needed to fill out the Force’s prescribed strength took time to produce and deploy to Vietnam. It was not until 1968 that the full complement of 180 river assault craft was reached, but fortunately, by the summer of 1967 there were enough boats on hand to carry out sustained search and destroy missions. These boats were rather unique vessels, and with one exception, were modified landing craft (LCM-6s).

The main craft of the River Assault Squadron were armored troop carriers (ATCs) which were capable of carrying a full infantry platoon. Armed with a 20mm cannon, two .50 caliber machine guns, and two Mark 18 grenade launchers, plus various hand held weapons, the ATCs not only landed troops, but also resupplied them and provided close-in fire support during operations. Since they were expected to get within close range of enemy forces these boats were well protected with both conventional and ‘stand-off’ armor. This ‘stand-off’ or bar armor was a series of metal rods a foot or so out from the ATCs hull and upper works and was designed to detonate RPG or recoilless rifle rounds before they hit the structural armor plate. ‘Stand-off armor’ proved to be very effective against both hand held and crew served weapons used by the VC, and significantly reduced casualties and damage when an ATC was hit by enemy fire.

Some armored troop carriers were modified with a helicopter flight deck counted over the troop wells. This was done initially to provide a platform for helicopters to land on for delivery of supplies and transfer of personnel. Almost immediately, however, the helicopters were pressed into service for casualty evacuation since they were often the only place for a helicopter to land during operations in the Delta. From this conversion came another, some of the armored troop carriers with helicopter pads, designated ATC(H)s, were fitted as battalion aid stations and carried a doctor and either Army or Navy corpsmen. During operations one ATC(H) also carried refrigerated whole blood and there was always a fully equipped operating table ready to perform emergency surgery.

Each river squadron also had an ATC fitted out as a refueler. These carried bladders of mogas or avgas under the flight deck to refuel the squadron’s boats, assault craft, and sometimes even helicopters. These refuelers proved indispensable during prolonged operations and pumped huge quantities of fuel to keep the riverine forces on station.

The main fire support vessel of the MRF was the Monitor. They were somewhat similar to the ATC from the stern forward to the troop deck, however, here all similarity ended. In a small open pit forward of the superstructure, an 81 mm mortar, similar to those aboard the Swift boats and Coast Guard cutters, was mounted. Forward of this a spoon shaped bow replaced the flat unloading ramp of the ATC. On this new bow was mounted a 40mm cannon (with a co-axial 50 caliber machine gun) enclosed in a turret. The 40mm was the main gun of the riverine forces and it provided a high volume of fire during landing operations. In addition, at least two Mark 18 grenade launchers were carried along with the individual weapons of the crewmen. Heavily armored, the Monitors often closed to within a few feet of the shore to provide fire support for the troops on shore.

Two Monitors in each squadron were also fitted out as Command Control Boats (CCBs). The only major difference between a regular Monitor and a CCB Monitor was the removal of the mortar in the pit aft of the 40mm turret. In its place a command and control console was fitted which served as the command post for the battalion and task group commanders during an operation. Otherwise the CCB Monitor was identical to a regular monitor and carried out much the same function.

The only boat specially constructed for use by the riverine forces was the Assault Support Patrol Boat (ASPB). In addition to providing fire support the ASPB was also designed to serve as a minesweeper and was fitted with a mine countermeasure chain drag. Lighter and faster than the Monitor, the ASPB was not as heavily armed or armored. It carried a single 20mm cannon and twin .50 caliber machine guns in two turrets, one in the bow, and one atop the superstructure. An 81mm mortar was mounted in the stern and two or more Mark 18 grenade launchers were also carried. The ASPB had a unique exhaust system which emptied out underwater making it the quietest of the riverine boats. Combined, these features allowed the ASPB to be used in a wide variety of roles. Aside from leading the river flotillas it was also employed for ambushes, patrols, special operations, reconnaissance, and escort missions. Later in the war, single or twin .50 caliber machine guns were added in stern while the forward gun turret had rocket launchers mounted on their sides. Linked to the machine guns the rocket launchers could be trained by elevating or depressing the machine guns and traversing the turret.

Besides these fighting boats, the Mobile Riverine Force had a number of support boats. Two self-propelled barracks ships (APBs) were modified for use in Vietnam. Each was fitted with a flight deck and equipped with air conditioning. Each could accommodate approximately eight hundred troops and provide some support for the river boats. In addition each APB was outfitted with an extensive communications system. The Benewah (APB-35) was equipped to serve as the brigade and flotilla flagship while the Colleton (APB-36) had similar arrangements for battalion and squadron commanders. In late 1967 the Colleton also received hospital facilities for the care of lightly wounded men.

However, since these two barracks ships could not handle all the men of the two infantry battalions, and artillery batteries, another barracks ship, non-propelled, supplemented the Benewah and Colleton. It could house another 625 men, but being unpowered, it had to be towed from place to place. This hampered the MRF since its movement was relatively slow and created tactical problems for the Riverine forces. Eventually two additional Self-Propelled Barracks Ships, The Mercer (APB-39) and Nueces (APB-40) were added to the Mobile Riverine Force to cut down on this problem.

To service and repair the various riverine boats and landing craft a repair ship was assigned to the support section of the task force. The USS Askari (ARL-30), a converted LST, provided a complete repair facility for the river craft. Cranes onboard could lift boats out of the water and deposit them on Ammi pontoons moored alongside for dry-dock work. In addition, the Askari also housed Army personnel who worked on weapons, radios, and engines. This ship provided indispensable service and without it the MRF would have been unable to keep its boats in service and carry out operations.

The last major support vessels of Task Force 117 were 1156-Class LSTs assigned to the flotilla from the 7th Fleet. These provided additional storage space which was unavailable on the APBs. In this space the LSTs housed supplemental supplies of ammunition, weapons, spare parts, and rations for reprovisioning the riverine forces during prolonged operations. These LSTs were equipped with a flight deck and carried the brigade’s helicopter detachment of four H-23s, along with one infantry company. They also supported a River Assault Division.

The final component of the riverine forces were the artillery and helicopter barges developed by the Army. Initially, it was envisioned that artillery would be put ashore to provide the necessary fire support. Very quickly it was discovered that there were few tracts of solid land in the Mekong Delta which could support artillery. To alleviate this problem an Army officer had a barge fabricated from sections of pontoons which enabled two 105 mm howitzers to fire while anchored next to the shoreline. These barges could also be beached if the tide went out and the artillery could be resighted, allowing the gun crews to keep firing their howitzers after only a slight delay. Helicopters also faced the same problems since there were few areas for them to set down. The ATC(H) provided only a partial solution, and the problem persisted. Similar to the artillery barges, a helicopter barge was developed using sections of pontoons. Each of these helicopter barges could accommodated three Hueys and were equipped with a refueling system which carried 1,500 gallons of JP-4 aviation fuel. Since neither of these barges were self-propelled, LCM-8s were used to move them for resupply of fuel and ammunition. These barges provided a quick and inexpensive solution to the problems faced by both artillery batteries and helicopter crews. As a result the MRFA did not lack for artillery or helicopter support.

Riverine Operations

River Raider I, the search and destroy mission carried out in the Rung Sat during February and March of 1967, was the first joint operation by Army and Navy forces. The Vietnamese Navy had provided some of the craft for use in the campaign since the full American contingent of vessels had not yet arrived. Throughout the spring of 1967 the Mobile Riverine Force gradually built up its strength, and carried out small local operations. During April and May the Kemper County (LST-854), the Benewah (APB-35), and the Colleton (APB-36) arrived in-country and began supporting the riverine craft. In mid-May TF 117 joined the TF 116 (Game Warden) forces to carry out the largest riverine operation by US forces to date in the Rung Sat. This operation also marked the first time both Task Forces worked together in support of one another.

Shortly after this joint operation was concluded, OPERATION HOPTAC XVIII was carried out in the area between the Rach Ba and Rach Tra Tan Rivers in IV Corps. Even larger than the Rung Sat operation, it resulted in the first heavy contact with the Viet Cong. After landing the infantry, the ATCs, supported by Monitors, blocked off the enemy’s line of retreat, and despite fierce fighting the VC were unable to escape the net thrown around them. Pressed from all sides they broke and ran, losing over 100 men. Casualties among the infantry and sailors were light and damage to the various river craft was minor. The boats had proven they could stand up to rocket and recoilless rifle fire, even at extremely close range, and their ability to block the VC’s escape had been the decisive factor in sealing the fate of the guerrilla force. Without them, the guerrillas would have been able to slip away to fight again.

Shortly after this operation was completed on 2 June, the MRF received a directive from MACV in Saigon, assigned the code name CORONADO to future riverine operations. Two days later CORONADO 1 began in Dinh Tuoug and Kien Hoa Provinces to secure the Cho Gao Canal. During the move up river to insert an infantry platoon ATC-112-3, acting as a minesweeper, had a mine detonate under its stern and had to be towed back to the new Army base at Dong Tam. This was the first successful mining of an MRF boat and highlighted the need for a specialized minesweeper. Unfortunately, while most of the remaining modified landing craft arrived during June, the ASPBs were not among them. The lack of these specially designed boats had some effects on operations but other craft were assigned the minesweeping duty until the ASPBs finally reached TF 117. Although without the ASPBs the Mobile Riverine Force was not up to authorized strength, the arrival of the last of the modified LCMs allowed the Navy to return borrowed riverine craft to the Vietnamese Navy without jeopardizing the force’s ability to carry out its mission.

Throughout the summer and fall of 1967 the riverine force was constantly on the move. In late June Coronado OPERATION CONCORDIA trapped a VC unit of some 400 men near Ap Bac. Together with ARVN units the soldiers and sailors of the MRF killed over 250 of the enemy while losing 46 men. Again the riverine craft helped cut the enemy’s line of retreat, and while heavy fire was taken, there were only fifteen sailors wounded during the battle. CONCORDIA II followed at the beginning of July and lasted until 24 July. During this campaign PBRs of TF 116 (Game Warden) assisted the MRF in blocking operations but their limited armor protection hindered their use in the close confines of the small canals where their primary protection, speed, could not be used effectively. At this time the MRF began operating H-23 and UH-1 helicopters off the ATC(H)s which increased the flexibility of the force’s reconnaissance and medivac ability. The first of the converted helicopter barges arrived on 22 July and was pressed into service immediately to supplement the ATC(H)s.

From August through October TF 117 carried out a series of operations against the VC in the Rung Sat Special Zone to keep the main shipping channel open. These included CORONADO III (5-17 August), CORONADO VI (11-18 October), and CORONADO VIII (27-29 October). None of these resulted in significant contact with large VC units. Only scattered resistance was encountered but these operations prevented the VC from carrying out attacks on the shipping channel due to this constant probing by the riverine force.

In conjunction with these forays into the Rung Sat the MRF also carried out a number of other operations in the surrounding areas. CONONADO IV (19 August to 9 September) took place south and southwest of Saigon in Long An, Co Cong, and Kien Hoa Provinces. Elements of the 506th VC Battalion were encountered and thirty-four of the guerrillas were killed. Numerous supply and arms caches were also discovered but contact was light. Close on the heels of this came CORONADO V (September 12th to October 8th) in Dinh Tuong and Kien Hoa Provinces, southwest of the capital. Working with US and ARVN troops from the 7th Division, the MRF encountered the 263rd VC battalion and in a series of running battles the allied forces killed over 500 of the guerrillas. However, the 263rd fought hard and eighteen Riverine boats were hit by rockets, grenades, and recoilless rifle fire. Though none were sunk, this was the heaviest fire that the MRF had yet come under. This underlined the ability of the boats to take a great deal of punishment and also the need for additional armament to counter the growing number of heavy caliber weapons being employed by the communists. During CORONADO V the first ASPBs arrived and received their baptism of fire. Toward the end of the operation the first attempt to use flame-throwers took place in Kien Hoa Province near Dong Tam with satisfactory results. An M-132 flame-thrower armored personnel carrier (APC) was placed in an ATC and tested under high wind conditions. No problems were encountered and additional M-132 were requested until a suitably modified monitor could be substituted for the ATC/APC arrangement. To help protect Vietnamese civilians during the 1967 National Elections Coronado VII (20-24 October) was conducted. During the elections the MRF dispersed itself throughout the Can Guioc District, but very little contact resulted. Over eighty per cent of the registered voters turned out die to the tight security the riverine craft and personnel provided. The year ended on a more resounding note combat-wise, with Coronado IX (1 November to 21 January). This long operation was started in part, to counter VC attacks against patrolling PBRs in the Giao Pue District.

Working with Vietnamese Marines the MRF met the Viet Cong twice during 1967 in large scale actions. Near the town of Sa Dec in mid-November a VC unit was cornered and in pitched fighting 178 of the enemy were killed. On 4 December at the boundaries between Dinh Tuong and Kien Phong Provinces, the allied force ran into both the 267th and 302nd VC battalions. Vietnamese Marines, with the aid of an ATC/APC flame-thrower, stormed ashore under withering fire while US units maneuvered to cut off the guerrilla’s escape. In two days of fierce fighting over 260 VC were killed against fifty US and Vietnamese casualties. Over forty riverine craft were hit by a variety of communist weapons, but none were sunk, and the majority continued to take part in the operation. After this battle contact dropped off sharply and the remainder of the operation turned into a mopping up campaign. When CORONADO IX was finally terminated, over 600 Viet Cong lay dead, US and Vietnamese fatalities were 100.

Tet

With the success of the various CORONADO OPERATIONS in 1967, VC power in the Mekong Delta appeared to be on the wain. However, this appearance was deceiving for in reality the communists were preparing a nation wide offensive operation against US and Vietnamese positions. On 29 January 1968, North Vietnamese and Viet Cong forces unleashed their Tet offensive, carrying out attacks across the length and breadth of Vietnam. In the delta region, the VC hit the major towns of My Tho, Ben Tre, Cai Lay, Cai Be and Vinh Long on 31 January.

The MRF, in the midst of CORONADO X redirected its attention toward My Tho where the situation was critical. Two battalions of troops were landed in the town and slowly cleared the guerrillas out in bitter house to house fighting. Within three days the town was deemed secure enough for the troops to be reembarked and redeployed toward Cai Lay, to cut off retreating enemy troops. Unfortunately most of these guerrillas evaded the MRF and little contact was made. After this fruitless foray, the MRF was dispatched to Vinh Long to support hard pressed ARVN troops. Moving into positions south of the city, the Riverine Craft and infantry successfully blocked the VC’s line of retreat and bitter fighting resulted as the guerrillas tried to break out of the area. However, the cordon was too tight and by 6 February the communist threat to Vinh Long was broken. These moves by the MRF over the short span of a week proved the ability of the riverine force to react rapidly and moved quickly over a large area. During this week the MRF inflicted over 600 enemy casualties in the fighting around My Tho and Vinh Long. Had it not been for TF 117, these important towns might have fallen to the enemy. But, with the ability to quickly move large numbers of troops from one hot spot to another the Riverine were able to effectively counter enemy attacks before they could gain momentum and achieve significant results. Perhaps the role of the MRF during Tet can best be summed up by General Westmoreland, the US commander in Vietnam, when he stated that “…the Mobile Riverine Force saved the Delta.”

1968 The Second Year

Following the Tet offensive, the Mobile Riverine Force continued to expand; in June of 1968 a third River Assault Squadron was formed, and, in July the entire force was reorganized into two sections: Mobile River Group Alpha and Mobile River Group Bravo. Another River Assault Squadron arrived in-country during September, and by fall the MRF had reached its full authorized strength in both combat and support ships. At this time, there were also changes made within the structure of the riverine infantry units which allowed more troops to be used as maneuvering elements, cutting down the number of men kept ashore at Dong Tam.

Along with these organizational changes and increases in force levels, the MRF also expanded its operating areas. Riverine forces with elements of the 2nd Brigade carried out a series of sweeps in Kieu Hoa Province under OPERATION HOMESTEAD. Action was light, as the enemy relied on small ambush teams armed with rocket launchers (RPG-2or 7) to harass the force. In October the two newly reorganized Mobile Riverine Groups (Alpha and Bravo) of TF 117 carried out additional missions throughout a number of provinces. Mobile Riverine Group Alpha remained in Kieu Hoa while Bravo worked in Vinh Binh, Vinh Long, Long An, Dinh Tuong and Phong Dinh Provinces. During October the two groups were reorganized vis-a-vis their River Assault Divisions (RADs). Group Alpha had five Divisions assigned to it while Group Bravo received three.

This shifting of assets resulted in each Group taking responsibility for a specific geographical section of the Mekong Delta in November. Group Alpha, with Riverine Assault Divisions 91,92,111,112,and 151, operated in the eastern delta while Group Bravo, with RADs 131,132 and 152, worked the western delta. Coinciding with this reorganization came renewed VC attacks against MRF support ships. On 1 November VC sappers placed mines on the hull of the Westchester County (LST-1167), the resulting explosions on the starboard amid ship ruptured the berthing, fuel and storage compartments, killing 26 sailors. After beaching for temporary repairs at Dong Tam the Westchester County went to Yokosuka, Japan for repairs; returning to Vietnam in March of 1969. Two weeks later a salvage barge was sunk by a mine with the lose of two lives. These attacks set the pattern for much of the remaining enemy action encountered by the MRF, and rarely were large groups of guerrillas spotted and brought to combat. Losses during Coronado operations and Tet, plus a healthy respect for the firepower of the riverine forces, caused the VC to revert back to guerrilla warfare where they concentrated on small scale hit and run operations. Throughout the remainder of 1968, TF 117 concentrated on pacifying the delta region and supporting ARVN troops. In addition, as the need arose, forces were assigned to OPERATION SEALORDS in cooperation with Market time and Game Warden units.

Vietnamization

During 1968 much thought was given to turning over more of the Riverine was effort to the Vietnamese. The first step in this process came about in January of 1969 when the boats of RAD 91 were withdrawn from combat to ready them for turnover to the Vietnamese. This was done on 1 February 1969, and shortly thereafter RAD91 was officially dissolved. From these assets, along with eight ASPBs the Vietnamese Navy formed River Assault and Interdiction Divisions (RAIDs) 70 and 71. This set the pattern for remainder of 1969 as the Riverine force prepared to hand over more of its assets to Vietnamese control. Operations continued to be carried out by the Riverine force but as the year progressed more and more effort was concentrated on training Vietnamese personnel to handle and maintain the various boats.

But while the strength of the MRF was being reduced, there was still a war going on, and the soldiers and sailors of the Riverine units continued to carry on with day to day operations. During these missions, the greatest threat to boats came from mines and underwater swimmers. A number of boats were sunk by mines and on numerous occasions VC sappers tried to attach charges to ships at anchor. Fortunately, these swimmers were kept in check by constant patrols around the anchorage’s. On occasion the VC staged ambushes along the rivers or canals with rocket launchers, recoilless rifles, and automatic weapons. But while casualties were usually light, and damage to the boats minimal, the sailors had to be ever on the alert against these attacks. The guerrillas also made mortar and rocket attacks at night against anchorage’s but the boat’s ability to move about helped to lessen the danger from this type of attack.

At the same time that the Riverine forces were turning over their assets to the Vietnamese, moves were a foot to redeploy the Riverine troops of the 9th Infantry back to the US. This was done gradually, starting in June, and resulted in a steady reduction in infantry assault units available for operations in the Delta. Their place was taken by ARVN units who worked with both their own Riverine forces and the remaining units of the MRF. This reduction in troop strength caused a drop in the tempo of operations and lessened the number of contacts with the VC. By the early fall of 1969 withdrawal of the 2nd Brigade was complete allowing the barracks ships, save one, to be withdrawn and returned stateside. Two more River Assault Divisions were turned over to the Vietnamese Navy, and the remaining units of TF 117 began working with a new unit, Task Force 194, which was given the job of conducting SEALORDS.

From the book “RIVERINE” by Jim Mesko