Task Force 117
Task Force 117, known as the Mobile Riverine Force (MRF), was a joint U.S. Army and Navy formation created during the Vietnam War to operate within the Mekong Delta’s maze of rivers, canals, and swamps. Conventional ground forces could not effectively maneuver in this environment, so the MRF was developed in 1966 to project infantry and firepower into areas only accessible by water. Its primary mission was to transport, support, and protect Army troops conducting search-and-destroy operations against Viet Cong forces embedded deep within the Delta’s river systems.
The force was built around the concept of a mobile, floating base. These bases included barracks ships, repair vessels, landing ship tanks, fuel tankers, and supply barges—all capable of moving with the operation. A complementary land base was also set up at Đồng Tâm, but the operational strength of Task Force 117 lay in its ability to deploy rapidly by river, strike hard, and then relocate as needed. It was one of the first large-scale attempts at sustained joint Army-Navy operations in a non-traditional combat setting.
The MRF’s key assault elements were the Armored Troop Carriers (ATCs) and Monitors. ATCs were converted landing craft designed to carry a platoon of infantry into contested areas. These craft were armored and typically mounted with multiple weapons for self-defense and fire support. Standard armament included two to four .50 caliber machine guns, several M60 machine guns, and sometimes 40mm automatic grenade launchers. For nighttime defense and illumination, they often carried Mark 18 40mm grenade launchers or hand-held flares. Some ATCs were even equipped with mortars for indirect fire support.
Monitors were more heavily armed gunboats designed for close support. They typically mounted a 40mm cannon in a turret, a .50 caliber machine gun, a 20mm cannon, and in some cases a flamethrower mounted in the bow. These craft provided suppressive fire as infantry landed, engaged fortified enemy positions, and acted as mobile firebases during extended engagements.
Patrol Air Cushion Vehicles (PACVs), or hovercraft, were one of the most unusual assets used by the MRF. Though few in number and experimental in nature, they could glide over both water and marshy terrain at high speeds. A typical PACV was armed with a forward-mounted .50 caliber machine gun turret and had side-mounted M60 machine guns for engaging targets at close range. Their speed and ability to operate in inaccessible terrain made them useful for surprise attacks and reconnaissance, but they were mechanically unreliable and too loud for covert movement. After limited success, they were eventually withdrawn from regular service.
The MRF also made extensive use of Patrol Boat, Rivers (PBRs), which were fast, agile, shallow-draft craft used primarily for interdiction, escort, and reconnaissance. These boats were powered by water jet propulsion systems, allowing them to operate in less than two feet of water and turn on a dime. A typical PBR mounted a twin .50 caliber machine gun turret on the bow, a single .50 caliber or 40mm grenade launcher aft, and sometimes an M60 on the port or starboard side. PBRs were instrumental in patrolling the narrow canals and escorting convoys, as well as inserting and extracting SEAL teams.
Support craft, such as minesweepers and landing craft mechanized (LCMs), also contributed to operations. Minesweeping boats used mechanical sweeps or sonar to detect and neutralize mines, often under threat from ambush. These craft were lightly armed with .50 caliber or M60 machine guns but relied on escorting gunboats for protection. Some LCMs were modified to carry mortars or recoilless rifles to provide mobile artillery support for infantry units operating near the banks.
Task Force 117’s operations included large-scale offensives such as River Raider I and the Coronado series, as well as a pivotal role during the Tet Offensive in 1968. During that campaign, the MRF was credited with helping prevent a complete collapse of control in the Delta, responding rapidly to enemy movements and reinforcing key positions by river. For its actions during this period, the unit was awarded the Presidential Unit Citation for extraordinary heroism and performance under fire.
The Mobile Riverine Force demonstrated how flexibility, speed, and integration of land and naval elements could overcome the limitations of terrain in a complex combat environment. Its combination of specialized craft, mobile logistics, and coordinated firepower created a new model for modern riverine and littoral warfare. The weapons mounted on its boats—ranging from machine guns and grenade launchers to cannons and flamethrowers—allowed it to deliver heavy firepower quickly and with precision, even in the most inaccessible regions of Vietnam. The lessons learned from Task Force 117 continue to shape the tactics and tools of riverine and special operations forces to this day.
