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Naval Warfare

Assault Support Patrol Boat (ASPB) (Alpha Boat)

Armored Riverine Assault Boat [ 1969 ]

The Assault Support Patrol Boat - or Alpha Boat - was purpose-built for riverine operations by American forces in Vietnam.

Authored By: JR Potts, AUS 173d AB | Last Edited: 02/28/2020 | Content ©www.MilitaryFactory.com | The following text is exclusive to this site.

The Assault Support Patrol Boat (ASPB) - otherwise known as "Alpha Boats" - were the dedicated destroyers and minesweepers of the "Brown River" riverine fleet of the United States Navy in South Viet Nam during the Vietnam conflict. However, before the Alpha Boat was formally developed and delivered to Vietnam waters, it was the "Tango Boats" (ATC) that served as the multirole workhorses of the river fleet. Tangos were a waterborne craft designed specifically as platoon strength troop carriers but could also be utilized for resupply and fire support sorties. With the sort of lethal work that Tango boats were involved in - particularly in minesweeping - it was unfortunately common for limitations to present themselves during missions that often times resulted in loss of crew or troops. Assault and minesweeping mission after-action reports and the growing mission requirements therein were sent to Gunderson Brothers Engineering Corporation of Portland, Oregon. Engineers there developed a new boat specifically for Brown River assault and minesweeping operations that ultimately became known as the ASPB, or simply, the "Alpha Boat".

The Alpha Boat displaced at 36.5 tons with a running length of 50ft, 1.5in and a width (or "beam" in ship-speak) of 15ft, 2.5in. A typical quality of such river boats was in a shallow draught, the Alpha able to traverse 4ft, 3in of water. To get where the action was, the Alpha Boat designers utilized 2 x General Motors 12V71 diesel engines of 430 horsepower each that, at least on paper, could make headway at 16 knots in perfect conditions. To give the boat endurance, she carried some 650 gallons of diesel fuel, allowing an operational range of 130 nautical miles when at 10 knots speed. The crew of five consisted of a captain/coxswain, radioman, engineer/gunner a .50 caliber heavy machine gunner as well as a 20mm autocannon gunner. Each boat cost the American tax payer $325,000 and all were made of steel for maximum durability under stress loads.

The first thirty-six boats were ordered from GBEC on October 25th, 1966 and the first ASPBs arrived at Vung Tau on September 20th, 1967. These boats were followed by another fifty craft ordered on January 24th, 1968. Crews were specially trained on the ins and outs of the new USN vessels which featured turret installations for primary armament and gunners. She was further fitted with a new mine countermeasure chain drag to run close to the river bank and clip (and ultimately detonate) any unseen enemy boobytrap wires. Normally, two Alpha Boats headed a column of US Navy boats while streaming their minesweeping gear and another Alpha was usually held aft of the column to bring up the rear.©MilitaryFactory.com
Alpha Boats proved lighter and faster than the Monitor - or "river battleship" - before them but Alpha Boats carried an arrangement of 2 x .50 caliber heavy machine guns as well as 2 x 20mm cannons across two turret emplacements - one held at the bow and the other on top of the superstructure. On the stern there was a multipurpose 81mm mortar for indirect fire. Additionally 2 x Mark 20 automatic grenade launchers, each with a rate-of-fire equal to 250 rounds per minute, were fitted and could reach target areas out to 400 meters. Naturally, any personal crew-served weapons could also be brought to bear as needed. All that said, Alpha Boats certainly packed a punch when called to support other navy craft or ground forces near the river.

The Alpha Boat ultimately helped to curtail Viet Cong activity along the Mekong Delta and fighting around Vinh Long. The boat series also helped the Army of the Republic of Viet Nam (ARVN) troops that were hard-pressed themselves to fight a river war - Alpha Boats played a crucial role in blocking the VC line to an extent. These riverine forces inflicted over 600 Viet Cong casualties around the Vinh Long area alone. Alpha Boats helped gain momentum in these key areas and also served to reduce enemy attacks on friendlies along major river waterways. The US Commander in Vietnam, General Westmoreland, even commented on the actions of the Mobile Riverine Force by stating that they helped to "save the Delta". During 1968, Vietnamization was just ramping up and included Brown Water Navy elements turning over their boats to ARVN troops. Missions continued with these boats under Vietnamese control while US Navy troops concentrated their efforts on the training of new crews.

The Vietnam War ended on April 30th, 1975 when Saigon finally fell to the North, bringing an end to a dark military chapter in American history. Many river boats were therefore captured by the North Vietnamese and pressed into service with their new owners, many of these seeing operational service until the late 1990's - such was the value of these mighty USN river boats - and the powerful Alpha Boat - in this part of the world.©MilitaryFactory.com
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Service Year

United States national flag graphic
United States


Assault Support Patrol Boat

Not Applicable.

National flag of the United States National flag of Vietnam North Vietnam; South Vietnam; United States; Vietnam
(OPERATORS list includes past, present, and future operators when applicable)
Offshore Operation
Activities conducted near shorelines in support of allied activities.

50.0 ft
15.24 m
13.7 ft
4.18 m
3.8 ft
1.16 m

Installed Power: 2 x Detroit Diesel 12V71 engines developing 480 horsepower each at 2,330rpm.
Surface Speed
16.0 kts
(18.4 mph)
130 nm
(150 mi | 241 km)

kts = knots | mph = miles-per-hour | nm = nautical miles | mi = miles | km = kilometers

1 kts = 1.15 mph | 1 nm = 1.15 mi | 1 nm = 1.85 km
1 x 12.7mm Browning heavy machine gun in dual mount.
1 x 20mm cannon (later 2x).
2 x 40mm Mk 20 automatic grenade launcher.
2 x 40mm M79 single-shot grenade launcher.

Also can include any crew-served weapons as needed - assault rifles, pistols, machine guns, flamethrowers and grenades.

Supported Types

Graphical image of an aircraft medium machine gun
Graphical image of an aircraft heavy machine gun

(Not all weapon types may be represented in the showcase above)

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Starboard side view of the Assault Support Patrol Boat in waters

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