Tank classification is a taxonomy of identifying either the intended role or weight class of tanks. The classification by role was used primarily during the developmental stage of the national armoured forces, and referred to the doctrinal and force structure utility of the tanks based on design emphasis. The weight classification is used in the same way truck classification is used, and is intended to accommodate logistic requirements of the tanks.
Many classification systems have been used over a hundred years of tank history. An early division in the definition of roles was between infantry tanks intended to focus on supporting infantry in the assault, and cruiser tanks intended for classic cavalry missions of exploitation, screening and reconnaissance. As World War II progressed, the separation of "infantry" and "cruiser" roles generally disappeared and the "universal tank" started to take over.
Classification has always been determined by the prevailing theories of armoured warfare, which have been altered in turn by rapid advances in technology. No one classification system works across all periods or all nations; in particular, weight-based classification was inconsistent between countries and eras.
With the worldwide adoption of the modern main battle tank designs, which favour a modular universal design, these sorts of classifications are mostly eliminated from modern terminology. All main battle tanks are typically armed with weapons with similar characteristics but some may be armoured more than others. These are complemented with light tanks, typically in the role of (armed) reconnaissance.
Development of tank classification schemes
Development of a tank classification system started in World War I, when tanks were separated into light tanks and tankettes, medium tanks, and heavy tanks, based on size and weight. Heavy tanks were required to be large to cross trenches, and consequently weighed a lot. Medium tanks were smaller and had help to cross trenches so weighed less. Light tanks were much smaller and lightweight, allowing transport on lorries (trucks).
These tanks started to be used in different roles based on armour and mobility. Light tanks could provide mobile machine gun support for infantry, medium tanks could be used to react and exploit situational advantages, heavy tanks could be used for the main advance.
As tank doctrine developed, the role of tanks started to be defined. Initially based on naval ideas, in late 1916 Captain Giffard Le Quesne Martel (later Major General Sir) proposed a tank army formed of Destroyer tanks, Battle tanks (of Heavy, Medium and Light types), Torpedo tanks (utilising large trench mortars), Engineer tanks, Supply tanks and Ambulance tanks
During the inter-war years, British tank doctrine evolved through experimental trials and the works of J.F.C. Fuller, P.C.S. Hobart and B.H. Liddell-Hart. By 1936, these settled on the roles of light tanks for reconnaissance, infantry tanks to support an advance, and cruiser tanks in the cavalry role, using mobility to exploit situational advantages. The works were further explored by Heinz Guderian in the development of German tank doctrine and Blitzkrieg for the opening stages of World War II.
Other nations continued to use the light, medium and heavy designations. US and Soviet forces also incorporated the tank destroyer concept, allowing their light, medium, and heavy tanks to prioritise works with the infantry. Soviet and US forces added the concept of the flame tank, armed with a flamethrower.
During the course of the war, German forces added command tanks, specialised to the task of co-ordinating tank formations. This idea caught on with other nations. Development of British doctrine added howitzer-armed close support tanks, similar to the older torpedo tank role. These soon became critical to launching smoke, and post-war smoke dischargers became common on tanks. Both command and close support tanks were typically based on the type of tank they were supporting, so may not be considered a completely separate classification.
With the fall of France, the need for infantry tanks to advance with troops started to be replaced with a need for Assault tanks, a new class with heavier frontal armour to take on battlefield defences. Infantry tanks proved capable in this new role however, and the designation was rarely applied outside of experimental production. The term saw limited use with both British and US forces in joint development. Hobart would later return to Martel's idea of Engineer tanks in the 1944 run-up to D-Day with Hobarts Funnies, and specialised tanks became a core component of the modern battlefield.