Service HISTORY

The Monitor was similar in many respects to the Armored Troop Carrier (ATC). The Monitor was 60.5 feet (18.4 m) long with a 17.5 feet (5.3 m) beam and a 3.3 ft (1.0 m) draft. Displacing 66 short tons (60 t), it could achieve a top speed of 8 knots (15 km/h; 9.2 mph) knots with its twin Gray Marine 225-hp diesel engines, however, armor and weapons reduced the effective speed to 4-7 knots. High-hardness XAR-30-type steel and bar armor provided ballistic protection for the crew from rounds up to .50 caliber in size and offered some protection against high explosive antitank rounds up to 57mm. Below-waterline hull blisters provided added hull protection, minimized draft, and increased stability.

The chief difference between the Monitor and the ATC could be seen in the well deck area. Monitors had a rounded bow as opposed to a drop-down ramp, making them slightly longer than the ATC (60.5 feet vs. 56 feet). They also mounted additional weaponry—a 40mm gun turret forward and an 81mm mortar amidships—and carried four additional sailors to help man those weapons and operate the boat. The 81mm mortar was the only indirect-fire weapon fielded by River Flotilla 1 and, with the assistance of an artillery observer, could hit targets up to 4,000 yards (3,700 m) away. Like any mortar, however, this one had a low muzzle velocity, making it ineffective against hardened enemy positions such as bunkers. The Monitor’s main weapon was the 40mm cannon—a very accurate direct-fire weapon that packed a tremendous punch. The 40mm cannon was the only weapon in the Mobile Riverine Force's inventory capable of smashing mud bunkers, but the rounds tended to damage rather than destroy these fortifications, allowing the Vietcong to quickly repair and reuse them for future ambushes. The 40mm guns also had such great range that Monitor crews had to take great care not to hit friendly forces or civilians when employing them.