Heavy tank is a term used to define a class of tanks produced from World War I through the end of the Cold War. These tanks generally sacrificed mobility and maneuverability for better armour protection and equal or greater firepower than tanks of lighter classes. Role Heavy tanks achieved their greatest, albeit limited, success when fighting lighter tanks and destroying fortifications. Heavy tanks often saw limited combat in their intended roles, instead becoming mobile pillboxes or defensive positions, such as the German Tiger designs, or the Russian KV designs Design Heavy tanks feature very heavy armor and weapons relative to lighter tanks. Many heavy tanks shared components from lighter tanks. For example, the M103 heavy tank shared many components with lighter Patton tanks, including transmission and engine. As a result, they tend to be either underpowered and comparatively slow, or have engine and drive train reliability issues. In case of an entirely new design development, which was the case with the German Tiger I, designs often became needlessly complex and costly, resulting in low production numbers. Although it is often assumed that heavy tanks suffered inferior mobility to medium tanks, this was not always the case, as many of the more sophisticated heavy tank designs featured advanced suspension and transmissions to counteract this drawback. As mentioned previously, heavy tanks are often extremely expensive and resource-intensive to produce and operate. The German Tiger I, for example, had similar speed and better terrain-handling characteristics when compared to its main competitor, the significantly lighter Panzer IV medium tank. However, low reliability and limited resources meant that just 1,347 were produced, compared to roughly 8,800 Pz.Kpfw. IV. History The origins of the class date to World War I and the first tank designs, which were intended to operate in close concert with infantry. Virtually all early tanks possessed thick armor to allow them to survive in no man's land. As lighter and more maneuverable designs were introduced during the Interwar period, these larger vehicles with stronger defensive and offensive capabilities became known as "heavy" tanks. Heavy tanks had gradually progressed from their trench warfare and bunker destroying role to dedicated anti-tank purposes by the onset of World War II. Heavy tanks saw limited deployment by France at the beginning of the war, and were only ever used in conflict by Nazi Germany and the USSR from about 1943 to the war's end. This tank