Panzerkampfwagen VIII Maus was a German World War II super-heavy tank completed in late 1944. It is the heaviest fully enclosed armoured fighting vehicle ever built. Only two hulls and one turret were completed before the testing grounds were captured by the advancing Soviet forces.
These two prototypes (one with, one without turret) underwent trials in late 1944. The complete vehicle was 10.2 metres (33 ft 6 in) long, 3.71 metres (12 ft 2 in) wide and 3.63 metres (11.9 ft) tall. Weighing 200 metric tons, the Maus's main armament was a 128 mm KwK 44 gun (55 calibers long barrel), based on the 12.8 cm Pak 44 anti-tank artillery piece, with a coaxial 75 mm gun. The 128 mm gun was powerful enough to destroy all enemy armored fighting vehicles at close or medium ranges, and even some at ranges exceeding 3500 meters.
The principal problem in development of the Maus was finding a powerful enough engine for its weight that could be carried in the tank. Though the design called for a maximum speed of 20 kilometres per hour (12 mph), no engine was found that could power the prototype to more than 13 kilometres per hour (8.1 mph) under ideal conditions. The weight also made it impossible to cross most bridges; it was intended to ford or submerge and use a snorkel to cross rivers.