The War in Vietnam's Shallows

While the land and air battles of the Vietnam War raged, the shallow waters off Vietnam’s coast and in the maze of rivers and canals in the Mekong Delta provided the U. S. Navy with a proving ground for patrol operations. New patrol boat types were introduced and old models adapted; new weapons and equipment were fielded; and innovative patrol tactics were developed. Eventually, combined with air and land actions, the Market Time, Stable Door, Game Warden, and SEALORDS operations disrupted the flow of communist material on Vietnam’s waterways.

The French Indochina War and Vietnamese Navy operations from 1954 to 1965 clearly indicated that craft of all types were needed to patrol the coastal waters, rivers, and canals of Vietnam. Before 1965, however, the U. S. Navy was reluctant to develop new craft or to create sizeable patrol forces. Naval leaders were more concerned with the Soviet naval threat, and thus emphasized major ship construction. They assumed that destroyer escorts and ocean minesweepers could handle Pacific coastal operations, and that amphibious landing craft could be modified to patrol inland waterways. However, a combined U. S.-Vietnamese patrol of the Vietnamese coast in 1962 demonstrated that existing ships, such as destroyer escorts and minesweepers, often could not operate effectively in the shallow waters off Vietnam. Moreover, South Vietnamese river operations revealed deficiencies with converted landing craft, especially their speed and maneuverability.¹

Thus, when the U. S. Navy was called upon to play a major role in the expanding Vietnamese conflict in 1965, the fleet had few coastal or river craft and few new models being developed. Significant exceptions included: two U. S. torpedo patrol (PT) boats built in the early 1950s; a small number of Nasty-class fast patrol boats (PTFs) purchased from Norway and deployed to Da Nang, South Vietnam, for coastal raiding operations; and U. S.-built Asheville-class motor gunboats, later designated patrol gunboats (PG-84 class). Of the latter, only two units were programed for production each year from 1963 to 1965. The lead ship of the class was not commissioned until 1966.²

Market Time: The Navy’s first major operation in Vietnam—the Market Time coastal patrol—was mounted by a hastily assembled assortment of ships and craft. Tasked with interdicting communist intercoastal and intracoastal movement, Market Time began on 11 March 1965, following the discovery of a 100-ton North Vietnamese trawler unloading arms and ammunition at an isolated cove in South Vietnam’s Vung Ro Bay. Eventually, the U. S. Coastal Surveillance Force (Task Force 115) deployed destroyers, ocean and coastal minesweepers, and radar picket escorts (DERs) to the Vietnamese coast. These units joined the South Vietnamese Navy’s submarine chasers, escorts, minesweepers, motor gunboats, and the paramilitary Junk Force.³

Soon the U. S. Navy augmented the patrol force with units more suited for patrolling the shallow, often rough waters off South Vietnam. The first action was to call on the U. S. Coast Guard, which came to the rescue with 17 air-conditioned 82-foot cutters (WPBs). Then the Navy procured 50-foot, 23-knot Swift fast patrol craft (PCFs), originally designed as civilian commercial craft, from the Sewart Seacraft Company in Louisiana. The Swifts, armed with three .50-caliber machine guns and an 81-mm. mortar, were manned by five sailors. The PCFs eventually formed the core of the Coastal Surveillance Force. Although the boats labored in heavy seas and suffered hull corrosion problems, they were well-suited to the patrol mission off Vietnam. Complementing these units after 1967 were the Asheville-class PGs, which carried a 3-inch/50-caliber gun forward, a 40-mm. gun aft, and two .50-caliber machine guns amidship. They were crewed by 25 men and powered by two diesel engines and a gas turbine capable of 40 knot speeds. Also joining Task Force 115 after 1967 were 15 heavily armed Coast Guard high- endurance cutters (WHECs). The PGs and WHECs were well-equipped for dealing with the armed communist trawlers that attempted to elude the coastal patrol. On a number of occasions, these and other allied units destroyed enemy vessels at sea or forced them aground, where friendly forces seized their cargoes of munitions and other contraband.⁴

When fully operational, the allied coastal interdiction effort was a sophisticated operation employing mutually supporting naval, air, and ground forces. Far out in the South China Sea, P-2 Neptune and P-3 Orion patrol aircraft tracked suspicious craft in the area; Coast Guard WHECs, and Navy DERs and patrol gunboats, deployed along an outer surface barrier 40 miles from the South Vietnamese coast; and U. S. Swift boats, WPBs, and South Vietnamese junks formed an inner surface barrier focused primarily on intracoastal Viet Cong movement.

Stable Door: In April 1966, the U. S. Navy’s Mobile Inshore Undersea Warfare Surveillance Group 1 began to establish harbor defense and local area patrol units at key South Vietnamese ports. This operation, called Stable Door, used large personnel landing craft, Boston Whalers, and 45-foot picket boats armed with machine guns and small arms. Indirectly complementing the coastal interdiction effort were the U. S. Seventh Fleet’s naval gunfire support ships and amphibious forces, plus allied ground units that attacked the enemy’s base areas on the coast.⁵

The Coastal Surveillance Force directed these resources from its headquarters at Cam Ranh Bay and five coastal surveillance command centers spaced along the coastline.

Allied forces accomplished their mission of limiting communist infiltration by sea. Between 1965 and 1972, when U. S. naval forces spearheaded the surveillance operation, the communists were increasingly deterred from risking their 100-ton trawlers in South Vietnamese waters, except during periods of crisis when the needs of North Vietnamese and Viet Cong forces ashore warranted such risks. On one occasion during the 1968 Tet Offensive, five North Vietnamese steel-hulled trawlers headed south. Task Force 115 destroyed three of them and the other two aborted their missions. During the eight-year coastal interdiction campaign, all but two of the more than 50 infiltrating units detected by the Coastal Surveillance Force were either destroyed or forced to abandon their mission of landing arms and supplies on the beaches of South Vietnam.⁶ Infiltration by junks and sampans, as well as intracoastal enemy movement, continued throughout the war. However, the increasingly effective coastal patrol system limited the amount of heavy weapons, ammunition, and other equipment supplied by this means to Viet Cong and North Vietnamese troops.

The key to the success of the coastal patrol operation was not any one or even several particularly effective patrol boats or craft (although a number of types were well- suited to the task). Rather, it was the coordinated, flexible, and complementary use of the many assets available to allied forces: long-range patrol aircraft; patrol gunboats, motor gunboats, destroyers, DERs, and high-endurance cutters armed with heavy weapons and surface-search radar; fast, shallow-water patrol boats; junks; harbor defense craft; and mobile ground units. These assets provided a comprehensive, continuous campaign of identification checks on fishermen and boarding of suspicious vessels, which resulted in the close monitoring of the coastal commerce and fishing fleets off South Vietnam.

Indirectly related to the success of Market Time was the availability to the communists of other longer but more secure routes of infiltration into South Vietnam. Between 1966 and 1969, Cambodia’s Norodom Sihanouk allowed communist freighters to unload their cargoes of arms and ammunition at the port of Sihanoukville on the Gulf of Siam. From there the material was secretly transported to the nearby South Vietnamese border and carried across on foot or in sampans into the Mekong Delta. In addition, by the end of the war, the Ho Chi Minh Trail through Laos had become a sophisticated and well-defended logistic system that adequately supplied enemy forces in the I and II Corps areas in northern South Vietnam. But the cost of developing this line of communication, which was less efficient than the sea route, was enormous in terms of diverted security forces, laborers, and material resources.

Game Warden: Patrol boats figured prominently in another operational theater of Vietnam—the rivers and canals of the extensive inland waterway system. Early in the conflict, U. S. leaders recognized that the Viet Cong relied heavily on water transportation to move supplies and personnel. To counter this, the U. S. Navy established the River Patrol Force (Task Force 116) with the primary mission of interdicting enemy traffic on the major rivers of the Mekong Delta—Operation Game Warden. Beginning in 1966, the Navy deployed river forces formed around the Mark-I river patrol boat (PBR). The Mark-I carried twin .50-caliber machine guns forward, a .50-caliber machine gun aft, a rapid-fire 40-mm. grenade launcher, surface radar, radios, and a crew of four bluejackets. Later, Mark-IIs, which had more-powerful water-jet pumps and a sturdier hull, were deployed. Normally, ten-boat PBR sections operated along a designated stretch of river from shore bases or from tank landing ships anchored in the rivers. Attached to each PBR section was a two-helicopter unit from the U. S. Navy’s Helicopter Attack (Light) Squadron 3 (HAL-3). The Navy also tested several experimental patrol air cushion vehicles (PACVs) in Southeast Asia. However, the PACVs proved to be too noisy and too mechanically sophisticated for the austere operating environment.⁷

Several problems limited the effectiveness of River Patrol Force operations from 1966 to early 1968. Because only about 150 PBRs were deployed to South Vietnam, they could patrol only the large Mekong Delta rivers. And aside from the support of the Navy’s helicopter squadron (the “Seawolves”), U. S. and Vietnamese resources were not coordinated to interdict Viet Cong traffic on the inland waterways. Hence, allied ground and air commands, naval combat units, police forces, and local government organizations often conducted their activities in virtual isolation from one another.

The enemy eventually adapted to the river patrol operation by shifting many logistic routes to the lesser rivers, canals, and swampy areas of the delta. The PBR units rarely left the major branches of the Mekong. In addition, the Viet Cong learned to evade waterway patrols and skirt police checkpoints. The communists also chose the time and place to ambush allied patrol units, which were necessarily spread thin and on the defensive.⁸

Naval leaders learned that river patrol operations were most effective when combined with the actions of other U. S. and Vietnamese forces. This was dramatically shown during the 1968 Tet Offensive, when PBR units, monitors, assault support patrol boats (ASPBs), and armored troop transports of the Army-Navy Mobile Riverine Force joined with Vietnamese Navy river assault groups to meet the communist threat. These naval units coordinated with ground and air forces to defeat Viet Cong attacks on cities throughout the Mekong Delta. Similarly mixed combat forces secured Hue’s Perfume River and the Cua Viet River just south of the demilitarized zone—critical friendly supply routes that helped heavily engaged allied ground troops turn back the communist offensive in South Vietnam.⁹

SEALORDS: By late 1968, the U. S. command had recognized the advantage of using integrated forces. Naval leaders conceived a new strategy for curtailing communist logistics traffic on inland waterways. Vice Admiral Elmo R. Zumwalt, Jr., the new Commander Naval Forces Vietnam (ComNavForV), inspired the Southeast Asia Lake, Ocean, River, Delta Strategy (SEALORDS), a systematic, coordinated, and combined campaign to interdict Viet Cong infiltration from Cambodia and hit the enemy’s supply bases deep in the Mekong Delta.¹⁰

In a departure from previous methods of operation, ComNavForV employed units for SEALORDS from each of the Navy’s major in-country commands. These included the reinforced River Patrol Force, the Coastal Surveillance Force, and the Riverine Assault Force (Task Force 117). The latter was the naval component of the Army-Navy Mobile Riverine Force. Also used in this campaign were: the Navy’s SEAL (sea-air-land) commandos, a river squadron operating the new strike assault boat (STAB), the 25 helicopters of HAL-3, and 15 heavily armed, fixed-wing OV-IO Bronco aircraft from Light Attack Squadron 4 (VAL-4). In line with “Vietnamization,” which began in 1968, many of the Vietnamese Navy’s 655 ships, assault craft, patrol boats, and other craft augmented SEALORDS. The naval command also took steps to ensure responsive support by U. S. and Vietnamese regular, regional, and local ground units plus the Vietnamese police.¹¹

Admiral Zumwalt, as Commander Task Force 194, commanded the SEALORDS operation through his deputy, dubbed the “First SEALORD.’’ In the First of two phases, the allies established barrier operations in November 1968 along major canals and rivers paralleling the border with Cambodia. By January 1969, U. S. and Vietnamese naval forces patrolled an interdiction line that ran from the Gulf of Siam east through the Delta to Saigon. To enhance allied patrol, interception, and ambush operations, the U. S. Navy established a sophisticated network of electronic sensors along the barriers.

In Phase II, launched in April 1969, combined forces struck at the Viet Cong in their previously inaccessible delta strongholds in the Ca Mau Peninsula, the U Minh Forest, and the mangrove swamps at the mouth of the Mekong.

The allied presence in these enemy “rear” areas was maintained from river mouth operating bases and a floating base anchored in the middle of the Cua Lon River. This massive pontoon barge was appropriately called “Sea Float.”¹²

Between late 1968 and early 1970, the SEALORDS campaign made significant progress in disrupting the logistic system supporting Viet Cong forces in the Mekong Delta. The Viet Cong reacted violently to the barrier and base area penetration operations. Despite this opposition, the allied effort delayed and diminished the enemy’s resupply and reinforcement. Allied forces seized or destroyed tons of enemy weapons, ammunition, and supplies, and killed 3,000 Viet Cong guerrillas. U. S. and Vietnamese losses totalled 186 killed.¹¹

Almost as debilitating for the communist military position in the southern regions of South Vietnam was the allied incursion into Cambodia. River forces played an important role in this campaign as well. On 9 May 1970, a Vietnamese-U. S. flotilla composed of PBRs, PCFs, ASPBs, various assault craft, and support ships steamed up the Mekong River into Cambodia. South Vietnamese units proceeded as far north as Phnom Penh, the Cambodian capital. Thereafter, naval forces interdicted communist east-to-west supply lines and curtailed enemy traffic on the Mekong itself.

Combined with the loss of Sihanoukville as a port of entry for munitions destined for South Vietnam and the disruption of the supply system in the Cambodian border area, the SEALORDS campaign drastically reduced communist military strength in the regions north and west of Saigon. SEALORDS’ success in the Mekong Delta probably was a major factor in the communist decision to launch their attacks elsewhere during the countrywide Easter Offensive of 1972.¹⁴

From 1965 to 1972, U. S. and Vietnamese naval patrol forces reduced enemy fighting strength in two key operational theaters of the war in Vietnam: the coastal region and the strategic Mekong Delta. That the South Vietnamese were unable to maintain military or political control of these areas in subsequent years does not diminish the earlier allied accomplishments.

Naval leaders learned, as the result of hard experience, that patrol boat operations were most effective when conducted with surface, air, and ground forces. Although the U. S. Navy had only a few modem patrol units at the onset of major combat in 1965, it drew on foreign and domestic manufacturers, the Coast Guard, and its own resources to equip powerful, versatile naval forces. By means of tactical and strategic innovation—and hard fighting—these naval units accomplished their mission-—securing the coastal and inland waterways of South Vietnam.