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. Not 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).In the Wake of the Tank - The first eighteen years of mechanisation in the British Army; Lieut.-Col. G. Le Q. Martel; Revised and enlarged 2nd Edition, 1936
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 tanksA Tank Army; November 1916; G. Le Q. Martel, Captain G.S.
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.
Towards the end of the war, increases in tank engine power started to create the possibility of multi-role vehicles. British light tanks had largely been replaced with armoured cars and carriers, and engineers proposed a new Universal tank coupling Cruiser tank mobility with Infantry tank armour. The concept became redundant when Cruiser tank armour increased anyway, rendering the infantry tank obsolete.
Post-war the light, medium, and heavy designations remained prevalent until the multi-role concept evolved into the main battle tank, rendering the earlier medium and heavy designations obsolete. Heavy tanks were largely withdrawn from service as medium multi-role vehicles offered similar capability with less of the weight-based constraints. Light tanks remained in use for flexibility, such as with air-portable use.
Size classifications Tanks are often referred to by weight-based classifications such as 'light', 'medium' or 'heavy', and by extension the role that this size of tank was suitable for. There were many names given to different tank types, and similar names did not assure similar design goals. Some light tanks were relatively slow, and some were fast. Some heavy tanks had large-calibre, low-velocity, anti-infantry bunker-busters, and some had high-velocity anti-tank guns. Furthermore, expected weights for a given tank type vary over time; a medium tank of 1939 could weigh less than a light tank of 1945.
While originally based on weight, the light, medium, and heavy classifications expanded based on tactical use. They now have other meanings than just weight, including relation to gun size, the amount of armour, and, most importantly, tactical role. Post-war in 1948 France, Canada, and the United States agreed to classify tanks as light gun, medium gun, or heavy gun.
After World War II, less expensive armoured cars and more specialised tracked vehicles gradually took over the roles of light tanks.
Heavy tanks were shown to be incapable of keeping up with mobile warfare, but advances in engine, weapon, and armour technology allowed medium tanks to acquire the best characteristics of heavy tanks, allowing them to fulfil multiple roles on the battlefield. The ultimate in mobility, firepower, and protection were rolled into the main battle tank (MBT). In 1957, the Fourth Tripartite Armour Conference recommended to replace medium and heavy tanks with a single class – Main Battle Tanks. p.123
World War I
In World War I, the first tank, the British Mark I, was designed for supporting infantry by crossing trenches and attacking machine-gun posts. This became known as a heavy tank alongside other, lighter, types.
A lighter British tank introduced into service in 1918, at and armed with machine guns only was given the designation "Tank, Medium Mark A" and known as the "Whippet".
The two-man French Renault FT was known as a light tank.
Super-heavy breakthrough tanks such as the Char 2C () or the K-Wagen () were nearly completed before the war ended. In comparison, the current British MBT, the Challenger 2, weighs some .
Interbellum
British tank designs in the immediate post-World War I era were developments along the same design as the Mark A and were named as Mediums being around . The first tank to enter service that broke with the design was known as the "Vickers Light Tank" (it weighed about ). It was renamed as the Medium Mark I in 1924 as the earlier heavy and medium tanks went out of service and lighter tanks – or less – came into service.B. T. White, "British tanks 1915–1945", p. 35
World War II
In World War 2, Light, Medium, and Heavy tank applications to different roles were incorporated into doctrine. In the US, light tanks were expected to be used ahead of the main force, medium tanks to accompany the main thrust of attack, and by-their-nature slower heavy tanks being brought up to deal with any more significant opposition. In practice, US heavy tanks saw limited use due to the capacity limits of most dockyard equipment, preventing their delivery to the theatres of operation. This left a role-based classification, the tank destroyer, to evolve from the need to move artillery pieces and set ambushes for axis tanks. A variety of super-heavy tanks were also designed during World War II, although none ever saw combat or construction due to their impracticality.
The British retained some light tanks from the interbellum period, but otherwise moved to a new role based classification scheme.
Other countries started to move to a more role-based approach, for example, by categorizing tanks into cruiser tanks, breakthrough tanks, and fast tanks. The tanks themselves are still often referred to by light, medium and heavy weights based on the actual weight or the equivalent role (for example, a cruiser tank may be light weight but is used in a similar role to a medium). This continued until multi-role vehicles became available.
Modern Light tanks, such as the PT-76, continue to play an important role in tank warfare, however many are being replaced with IFVs and armoured cars. The light tank is still more used than main battle tanks in many armies for various reasons: financial, terrain-related (muddy landscape and dense foliage), or doctrinal dependence on airborne divisions. Many light vehicles, such as the British Combat Vehicle Reconnaissance (Tracked) series (FV101 Scorpion, FV107 Scimitar) are used primarily for reconnaissance, but retain the tank capabilities.
Medium and Heavy tanks were used in the early stages of the cold war, but have gradually been phased out by the multi-role Main Battle Tank. Heavy tanks grew to the point of being logistically problematic, such as the Conqueror and IS-3, while the MBT became capable of filling their battlefield role in a comparatively Medium form-factor. In most cases, the Heavy tanks grew so large that they could not be transported by rail, and could not be supported by common bridges.
Role classifications Many types are also described by their tactical role, which depends on contemporary military doctrine. For instance, 'infantry' and 'cruiser' tanks are British classifications of the 1930s and '40s; 'infantry', 'fast', and 'breakthrough' are Soviet types of the same time period.
British and Soviet tacticians up to the time of the Second World War classified tanks into three major roles: infantry, light, and cavalry. Infantry tanks supported infantry units, to integrally support dismounted infantry actions. Light tanks performed the traditional cavalry role of scouting and screening. Cavalry or "cruiser" tank units were meant to exploit breakthroughs and fight other armoured formations.