of the world's militaries employ more modern versions of the amtrack. One of the latest is the now cancelled United States Marine Corps Expeditionary Fighting Vehicle, that was slated to begin replacing the AAV in 2015 but was cancelled in 2011 after going significantly over budget. Variants The US Army used a different naming system from the Navy but instead of using the usual Army system of Model (M)-numbers, they referred to the LVTs by Mark number using Roman numerals rather than Arabic numerals. Hence the LVT-4 was the "Mark IV". In British service LVTs were given service names and mark numbers to distinguish them. LVT-1 The first military model. Traveling at a respectable laden in the water and on land, it could deliver 20 fully equipped assault troops to the beach and supply supporting fire from two .30 M1919 Browning machine guns though it was only intended for delivering supplies inland until wheeled vehicles could be brought ashore. It was powered by a Hercules WXLC six-cylinder petrol engine, mounted in a housing in the rear cargo hold. The LVT-1 was propelled on both land and water by tracks which were fitted with Roebling patented oblique shoes that gave good grip on land as well as good drive in the water. Apart of the forward driver's compartment, the bulk of the unarmoured steel hull was given over to a cargo area 21 ft 6 in by 9 ft 10 in which could be laden to . The hold was divided into several watertight compartments. 1,225 LVT-1s were built between 1941 and 1943, 485 were transferred to the US Army and 200 to the British Army. The LVT-1 had a maximum speed of on land or in water; and a range of on land or in water. No armor or weapons were included in its design as its role was cargo transport from ship to shore. Many vehicles were refitted prior to the Tarawa landing to hold two Browning heavy machine guns forward, with the .30 guns aft. The vehicle was not armored and its thin steel hull offered virtually no protection, although prior to Tarawa some vehicles received of armor plating to the cab. Tracks performed well on sand, but not on tough surfaces. The rigid suspension threw tracks and roller bearings corroded in salt water. Proper maintenance of the new machine was often an issue, as few Marines were