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UNITED STATES OF AMERICA

COASTAL FORCES

"ASPB Mk II" river assault support patrol boats (50AB701) (1970)

Project history: Riverine warfare required considerable numbers of escort craft to operate directly with the troop carriers. Both shallow-draft 'monitors' (MON) and Assault Support Patrol Boats (ASPB) were developed. The first monitors were converted from LCM(6) (landing craft) hulls, which formed the basis for may of the riverine craft. Later units (Mk V) were built as such from the keel up, and had rounded bows without landing craft type bow doors. They used the same hull as the CCB command boats, with a twin 20mm bow turret, an 81mm mortar in a well, and a smaller turret on the superstructure for a 7.62mm MG. Some had a 105mm howitzer in place of the bow turret and mortar well. Both types were armoured against shaped-charge rockets with characteristic armour slats like Venetian blinds. Numbers built are not available, but all survivors were handed to the South Vietnamese Navy in 1973. They included at least twenty-two converted LCM(6) - transferred 1964-67 - and forty-two purpose-built monitors.

    The ASPB (Assault Support Patrol Boat) was the only craft specially designed for the river war, described as the destroyer and minesweeper of that specialized fleet. It was equipped with a chain drag to counter command mines, and armed with a 20mm cannon, a twin 0.50cal MG, two Mk 18 grenade launchers, and an 81mm monar. ASPBs generally led riverine operations, sweeping ahead of the assault formation; they were also used as escorts, patrol craft, and counter-ambush craft. One unusual feature was the underwater exhaust system, adopted for silencing. The ASPB was built in two Marks in 1967-68. with welded steel hulls, and capable of about 14kts (compared to 16kts as designed). The ASPB hull was also used for minesweeping (as the MSR) and for CCB duties. At least eighty-four ASPB were transferred to the South Vietnamese Navy and the remainder discarded.

    Troops were generally carried in converted LCM(6)s, ATCs (Armoured Troop Carriers), each carrying a platoon of about 40 men. Some were fitted with helicopter decks as ATC(H), serving as batallion aid stations. In addition, until the arrival of the specially designed ASPB, the ATCs were the the minesweepers of the Riverine Force. Postwar, a new 'mini-ATC' was developed, primarily for Special Forces-type operation, with an aluminium hull and ceramic radar, quiet engines (for 28kts), shallow draft (0.3m), and space for up to seven pintle-mounted weapons. By 1981, a total of 18 had been delivered, one powered by gas turbines.

For command and control, the Riverine Navy had CCBs, converted from LCM(6)s and similar to the monitors except that a command module replaced the 81 mm mortar of the latter, it was inserted between the after superstructure and the covered gun position in the bow. The latter could accommodate one 20mm or 40mm gun, and there were typically several 7.62mm and 12.7mm machineguns

    Numbers of convened craft are somewhat difficult to fix. The United States initially modified LCMs for Vietnam. The initial series of transfers (planned in 1961) amounted to sixteen LCVP and sixteen LCM (command boats and monitors). They began to arrive in 1963. Ten LCMC command boats were transferred in December 1963, followed by four in 1966. The first seven US monitors were transferred in December 1963, seven more in March and June 1965, and eight more in 1966. There were also LCM troop carriers, denoted LCM-C (LCM-combat). Transfers included at least twelve in December 1963, eight in December 1965, and twenty-four in 1966. The Vietnamese also had similar craft converted by the French or by themselves. When the United States entered the war, new conversions to modified designs were begun. Totals were: twenty-nine monitors (ten Program 4, fourteen Program 5, five Program 6); thirteen command boats (CCB: four Program 4, eight Program 5, one Program 6), 124 armoured troop carriers (ATC: fifty-two Program 4, 64 Program 5, eight Program 6); and eight armoured refuellers (four Program 4, four Program 5, eight Program 6). Program 4, the original US riverine programme for two squadrons, also included two SEAL heavy support craft (HSSC). Ten of their successors, LCMMs, were included in Program 5. Program 4 (two riverine assault squadrons, FY67) had been drastically scaled down and did not include any allowance for losses. Program 5 (FY68) provided another two squadrons plus training and attrition boats. Program 6 was ordered late in January 1972; it included conversions for Cambodia. There were two types of Program 5 monitor, 105mm and flame-thrower.

    ASPB production: FY67 (Program 4): thirty-six (plus one test platform), FY68 (Program 5): fifty (fourteen delivered directly to South Vietnam); there were also ten very similar river minesweepers.

    Program 5 also included research and development for a next-generation lines of riverine craft, which were built only as prototypes.

Modernizations: None.

Naval service: Boats were actively used in Vietnam.

ASPB 1968

© Ivan Gogin, 2015