River monitor

River monitors are military craft designed to patrol rivers.

They are normally the largest of all riverine warships in river flotillas, and mount the heaviest weapons. The name originated from the US Navy's USS Monitor, which made her first appearance in the American Civil War, and being distinguished by the use of revolving gun turrets.

On 18 December 1965, the US Navy, for the second time in one hundred years, authorized the reactivation of a brown-water navy for riparian operations in South Vietnam. In July 1966, Secretary of Defense Robert S. McNamara authorized the formation of a Mobile Riverine Force (MRF); a force that would bring back the heavily armored single-turret river monitor.

River monitors were used on inland waterways such as rivers, estuaries, deltas and lakes. Usually they had a shallow draft which was necessary for them to be able to operate in enclosed waters; but their displacement, size and draft varied depending on where they were used.

Most river monitors were lightly armored although this varied, with some carrying more armor. Exceptional examples, however, most notably the Royal Navy's Lord Clive-class monitors, which could operate in coastal or certain riparian/estuarine situations, bore extra-thick armor plating and heavy shore-bombardment guns, up to a massive 18 inches (457 mm) in size. Typically, however, river monitors displayed a mixture of gun sizes from 3-inch (75 mm) to 6-inch (152 mm), plus machine guns. This type of vessel overlaps with the river gunboat.

On Asian rivers, the Amur Military Flotilla on the Amur used large Taifun-class river monitors of the Imperial Russian Navy from around 1907; the Imperial Japanese Navy captured some of these ships in 1918. They were up to 1,000 tons displacement, armed with 130 mm guns. Some of these Russian monitors, such as the recommissioned Sverdlov, were still in use by the Soviet Navy in the 1945 Soviet invasion of Manchuria.

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