Defending the Mekong Delta: Tet and the Legacy of the Brown-Water Navy

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On Jan. 31, 1968, Viet Cong and North Vietnamese troops attacked over 100 of South Vietnam’s cities and towns. The offensive on the evening of Tet, the Vietnamese lunar New Year, came as a complete shock to both the United States and the Republic of Vietnam. Over time, the allies reconquered almost all of the lost ground and inflicted significant losses on the enemy, but the scale and ferocity of the attacks proved a major political blow for the U.S. war effort in Southeast Asia.

For the U.S. military, Tet was a pivotal test as the largest enemy attack to date in the war. Two of the most critical battle areas of Tet were the northernmost military region of South Vietnam (I Corps) and the southernmost (IV Corps), which contained the Mekong Delta. When Tet occurred, IV Corps became a high priority for the U.S. Military Assistance Command Vietnam (MACV) because it was home to more than a third of the country’s 17 million people and the source of 75 percent of the nation’s food. It also abutted Saigon, the capital. In the Mekong Delta, the communists attacked 64 district capitals. Much of the defense of the delta fell upon the shoulders of U.S. Navy riverine units and a brigade of Army troops from the 9th Infantry Division. During the offensive, Navy small boats were employed for fire support, troop transport, amphibious assault, forward basing, logistical support, and numerous other missions. They, along with the U.S. Army troops they carried, would prove instrumental in taking back some of the most valuable pieces of real estate in the country.

The ability to operate and fight on rivers and shallow coastal areas (known as brown-water or inshore warfare) was critical to Tet and the broader war, but this capability had withered in the U.S. Navy since World War II. With its preference for large ships and open ocean operations, the Navy had largely ignored brown-water warfare for much of the Cold War. The Vietnam War and Tet in particular demonstrated that the U.S. Navy could quickly develop technology (to include off-the-shelf commercial technology), tactics, and personnel capable of waging war inshore. The story of how the Navy built a multi-mission, brown-water navy from scratch during the first three years of the war helps explain why it had such an impact during Tet. As the Navy continues to focus on lethality, it would be wise to remember both the struggles and triumphs of the “Brown-Water Navy” in Southeast Asia.

Origins: Operation Market Time

When U.S. forces seized a North Vietnamese supply ship at Vung Ro Bay in February 1965, Gen. William C. Westmoreland, the MACV commander, understood that the U.S. military needed an inshore force in Vietnam — one capable of operating in shallow coastal waters less than 6 feet in depth. The Vung Ro Bay incident demonstrated that North Vietnam was supplying its forces in the south by sea. Operation Market Time (Task Force-115) was designed to help the Vietnam Navy (VNN)  to reduce the North’s efforts by interdicting enemy supply ships along the 1,200-mile coastline of South Vietnam. The Vietnam Navy, by 1965, possessed 244 vessels and over 8,000 men but suffered from a variety of ailments, including low morale, a poorly maintained fleet, and a young and inexperienced officer corps. Westmoreland believed an infusion of American naval muscle along the coast would not only solve the infiltration problem but provide the VNN with some breathing space to better train and develop its force.

Task Force-115 grew to 5,000 personnel and 126 craft from two services (the U.S. Navy and Coast Guard) deployed along the coast at five separate bases. Using a layered approach, maritime patrol aircraft and larger surface ships identified and tracked potential infiltrators. Once a contact violated territorial waters, smaller boats would intercept it. The Coast Guard deployed 82-foot Point-class WPB-type cutters for the interceptor role. The Navy hastily acquired 50-foot commercial aluminum boats (known as Swift boats), and adapted them for the mission by adding a variety of weaponry, communications equipment, and radar.

Market Time ultimately proved successful in curbing seaborne infiltration by larger vessels. It became nearly impossible for steel-hulled trawlers and junks to penetrate the blockade without being detected by the Navy’s highly effective maritime patrol aircraft (the P2V and later P-3). Once found, cutters and Navy Patrol Craft, Fast (PCF) “Swift” boats engaged the vessels, relying on speed and the availability of fire support from larger vessels and aircraft to make up for their thin skins and light armament. By March 1968, North Vietnam had greatly curtailed its trawler operations along the coast and Market Time could boast of a 94 percent success rate in stopping steel-hulled infiltrators.

Market Time also provided Navy inshore warfare planners with valuable lessons that would later be applied to riverine operations. Lesson one was that to survive in a firefight with dug-in ground forces, small boats either had to be very fast or heavily armored. Both approaches would be tried with varying degrees of success later in the war. Another lesson was that every brown-water sailor had to possess a set of unique warfighting skills not generally found in the fleet. These included competencies with light weapons, advanced first aid, and small boat handling. In 1967, the Navy established the Navy Inshore Operations Training Center (NIOTC) at Mare Island, California, to teach these skills to sailors assigned to coastal and riverine units in Vietnam.

Operation Game Warden: The Navy’s Mission Expands to the Rivers

Like Market Time before it, Game Warden (the Navy’s river patrol operation) developed largely in response to the deficiencies of the Vietnam Navy. For much of the war, Vietnam Navy riverine boats were employed mainly to ferry and re-supply Army of the Republic of Vietnam (ARVN) units rather than to deny the enemy the use of South Vietnam’s rivers. The Mekong Delta alone contained over 3,000 miles of waterways. MACV could not hope to defeat the insurgency without establishing some semblance of government control there. Consequently, a 120-boat U.S. Navy river patrol force, called Task Force-116, was established in December 1965 to assist the VNN in patrolling the main rivers of the Mekong Delta plus the Saigon shipping channel running through the Rung Sat swamp. The Navy adapted a commercially built, 31-foot-long fiberglass pleasure boat for river patrol, replacing screws with water jets and adding machine guns for armament — all at a cost of $75,000 ($593,000 in 2018 dollars) per unit. Like the PCF, the Patrol Boat, River (PBR) was a cost-effective and innovative application of off-the-shelf technology to a military role.

In addition to showing presence, PBRs (capable of speeds in excess of 25 knots) searched suspicious watercraft, enforced curfews, and occasionally disrupted communist troop movements. Organized initially into five divisions, the PBRs operated from both dry land bases and Landing Ship, Tanks (LST). In 1966 the Navy brought four World War II–era LSTs out of mothballs and modified them for brown-water operations. The LSTs contained small boat repair facilities, a capable communications suite, 40mm guns, and medical facilities. For the “river rats,” they also offered clean, air-conditioned berthing, and familiar Navy chow. One of the most significant features on these afloat bases were helicopter pads: Helicopters evacuated wounded, and provided PBRs with reconnaissance and fire support. During the war, the Navy developed a light helicopter attack squadron specifically for riverine operations.

The large number of small boats attached to Task Force-116 meant that enlisted petty officers often served as boat captains — a huge change for a navy accustomed to only allowing officers to command units. The same would be true in the Mobile Riverine Force. In most cases, these enlisted boat captains exceeded expectations. Many proved to be fierce warriors, and received some of the nation’s top combat awards, including the Medal of Honor and Navy Cross.

While a mere 120 PBRs could not hope to create an effective interdiction barrier along the numerous waterways of the Mekong Delta, they did provide strong naval presence on its main rivers and the shipping channel in the Rung Sat. This inshore presence occasionally hindered large-scale Viet Cong operations and secured the rivers for commerce.

The Mobile Riverine Force

By 1966, the Viet Cong was prosecuting over 1,000 small-scale attacks per month on government posts and isolated villages in the Mekong Delta. The Mobile Riverine Force (MRF) grew out of Westmoreland’s desire to reduce these attacks by destroying main force units operating there. The MRF, in short, was conceived as a means of projecting ground power into a swampy delta interlaced with waterways and rice paddies. Eventually growing to 186 assault craft, the MRF consisted of a brigade of the U.S. Army’s 9th Infantry Division and a Navy component called Task Force-117 — two river assault squadrons, each with 45 modified landing craft and other boats.

Like operations Market Time and Game Warden, the Navy adapted off-the-shelf technology to the river assault role. However, this technology was not commercial in nature but military. Because the MRF would perform inshore amphibious operations, the Navy believed that existing amphibious landing craft technology, much of which was developed during World War II, would suffice if up-armed and up-armored. Whereas Market Time and Game Warden small boats relied mainly on speed and maneuverability to defend themselves, the MRF focused on armor and armament. It was much slower-moving as a consequence. In Army terms, it functioned more as an armored unit than cavalry.

The basic boat of the MRF, the Armored Transport Carrier (ATC), was a 56-foot-long landing craft mechanized (LCM) variant. Steel and bar armor provided ballistic defense for rounds up to .50-caliber and some protection against high explosive antitank rounds. Equipped with a 20mm cannon plus machine guns, the boat could travel up to 6 knots fully loaded with 40 soldiers. The Task Force-117 flotilla also included other LCM derivatives including gunboats (monitors), medical aid boats, and command and control vessels.

The only riverine boat developed completely from scratch during the war was the Assault Support Boat (ASPB). Designed to be the MRF’s destroyer, it was a combination escort, patrol boat, and minesweeper. The boat could achieve speeds up to 14.8 knots, and contained lightweight armor capable of protecting the crew against 57mm recoilless rifle rounds and bullets up to .50-caliber in size. While its sailors would have appreciated more speed and armor capable of withstanding direct hits from larger caliber rockets, no other riverine platform offered such capability and versatility.

Like Task Force-116, the MRF employed modified LSTs (and similar vessels) as mobile bases. It also developed a massive dry land base at Dong Tam near My Tho. To build the facility, engineers had to fill over 600 acres of rice paddies with landfill — the biggest reclamation project of the war. By mid-1967, Dong Tam occupied 12-square kilometers.

An LCM-6 is being used as a makeshift pier for U.S. Navy PBRs transiting to other bases. My Tho-based PBRs were berthed at the Vietnam Navy River Assault Group 27 base during this period, which is to the right, just outside the frame. December 1966.

Westmoreland placed all U.S. Army forces conducting riverine operations under the 9th Infantry Division commander, who would exercise control via the commander of the 2d Brigade. U.S. Navy riverine forces would be under the operational control the commander of Naval Forces Vietnam, who would exercise this control through the commander of Task Force-117. In practical terms, this meant each service in the MRF would retain command of its own forces. Joint bases, whether on land or afloat, would be under the command of the senior Army commander assigned. When the MRF weighed anchor, the Navy component commander would assume control until the movement was over. During combat a similar arrangement prevailed. Troops in landing craft would be under Navy control while in transit, but as soon as the troops landed, the Army commander would regain control.

Tet Arrives

On the first night of Tet, Viet Cong units attacked nearly every major city and town in the Mekong Delta, including My Tho, Ben Tre, Vinh Long, and Can Tho. Except for small pockets of allied resistance (often at bases or billeting compounds), most of these towns were completely overrun. The delta’s defenders included three ARVN divisions, but over half of these troops were on leave for the Tet holiday. Effectively, this meant that a large portion of the fighting would fall upon the U.S. Army 9th Division and naval forces. Riverine units performed two basic functions during the attack: mobile fire power and transport for Army troops.

Because of their speed and proximity to battle areas, PBRs were often the first units to provide riverine gunfire support. At Ben Tre, a city of close to 75,000 and the capital of Kien Hoa Province, the Viet Cong attacked early in the morning of Jan. 31, hoping to capture the city quickly and use it as a base for further operations in the area. Until units from MRF arrived at Ben Tre late in the day on Feb. 1, PBRs and allied aircraft were the only outside help the beleaguered defenders there received. Without U.S. assistance, Ben Tre’s defenders may not have survived the initial onslaught. During the battle, even support ships engaged in the fight. The LST Harnett County’s 40mm mounts delivered over 20,000 rounds in the Ben Tre area.

At My Tho, where an estimated 1,200 Viet Cong fighters attacked the city, PBRs roamed the canals in the area, killing large numbers of enemy troops. Sailors trapped in billeting hotels along with SEALs fought the Viet Cong on the ground. SEALs attached to Task Force-116 managed the effort, providing on-the-spot infantry training to rear echelon sailors more accustomed to manning typewriters than M-16s.

The tide of the battle of My Tho changed dramatically with the arrival of MRF units late in the afternoon on Feb. 1. Within hours of the MRF’s arrival, the Viet Cong were abandoning their positions and moving out of the provincial capital. Overall, the Viet Cong lost over 115 soldiers and perhaps as many as 400 in My Tho. By comparison, the MRF lost three soldiers and the ARVN, 25.

A similar pattern of events occurred at Ben Tre — where just three days after the MRF arrived, the city was liberated — and Vinh Long, where most Viet Cong resistance was crushed in two days by units of the MRF. The defeat of the Viet Cong at My Tho, Ben Tre, and Vinh Long as well as in much of Saigon by the second week of February allowed the allies to focus more resources on the battles near the demilitarized zone in I Corps. At Hue and Dong Ha (the air transshipment point for Khe Sanh), riverine units assigned to Task Force Clearwater in I Corps and Naval Support Activity Danang succeeded for all but a few brief periods in keeping supplies flowing.

Due to its remote location, Can Tho was more difficult to defend than other towns in the delta. To thwart a potential attack by a force of 2,500 Viet Cong, the MRF had to make a 110-mile journey from Dong Tam to Phong Dinh Province. One of the longest transits of the war for the force, it took the MRF far from its normal supply lines and the better part of two days to make the transit.

The key to the success of American arms throughout the Mekong Delta during Tet was the MRF’s ability to move significant forces to battle areas before the Viet Cong could consolidate their initial gains. The MRF transported forces to battlefields in eight provinces in February and sustained them once the battle was joined by providing gunfire support — a significant asset during Tet when aviation and artillery assets were in short supply — and ammunition, food, water, and medical aid. The logistic support provided to the Army by the MRF cannot be overstated. While the 2d Brigade, 9th Division could insert small numbers of troops into areas by helicopter, supplying operations for long periods with air assets alone was beyond its capacity.

Did the MRF save the delta, as Westmoreland allegedly told Capt. Robert Salzer, the Task Force-117 commander, after the battle? Not singlehandedly. While the mobility, firepower, logistical support, and amphibious capability provided by the MRF was the secret sauce that allowed Westmoreland to quickly reverse the Viet Cong gains and turn his attention to the battles occurring near the demilitarized zone in I Corps, other units also contributed mightily to the effort. Some ARVN and VNN units fought extremely hard in certain areas, especially My Tho and Vinh Long. Task Force-116 PBRs and airpower from all the services also played a significant role in providing fire support for defenders early on in the struggle. The fight for the delta was a joint and combined arms effort.

Vietnam was a watershed in many ways for the Navy. It represented the only time in its recent history that large numbers of sailors experienced riverine warfare in small boats — a combat experience more akin to that of an infantry soldier than a sailor on a large oceangoing surface combatant. The experience forged a strong warrior culture in the U.S. Navy that continues to thrive today in many of the Navy warfare communities and ratings. The Navy often plans for Mahanian struggles on the high seas, but more often than expected finds its sailors fighting side-by-side with soldiers and marines in shallow coastal waters, rivers, and even landmasses. This was true in Vietnam, the Civil War, and even more recently in Iraq and Afghanistan.


Dr. John Darrell Sherwood works as a historian for the U.S. Navy, and is the author of War in the Shallows: U.S. Navy Coastal and Riverine Warfare in Vietnam, 1965-1968. This article is printed with the permission of the U.S. Navy. The U.S. Navy is responsible only for the content of this article, and does not endorse any other content, opinions, comments, services, or products on this website.

All images via U.S. Navy