Panzer VIII Maus
Panzerkampfwagen VIII Maus ("Mouse") was a German World War II super-heavy tank completed in late 1944. It is the heaviest fully enclosed armoured fighting vehicle ever built. Five were ordered, but only two hulls and one turret were completed before the testing grounds were captured by advancing Soviet military forces.
History of the tank
Swinton proposed in a letter to Sir Maurice Hankey, Secretary of the British Committee of Imperial Defence, that the Committee build a power-driven, bullet-proof, tracked vehicle that could destroy enemy guns. Hankey persuaded the War Office - which was lukewarm to the idea - to make a trial on 17 February 1915 with a Holt tractor, but the caterpillar bogged down in the mud, the project was abandoned, and the War Office gave up investigations.