Armoured fighting vehicles are classified according to their intended role on the battlefield and characteristics. This classification is not absolute; at different times different countries will classify the same vehicle in different roles. For example, armoured personnel carriers were generally replaced by infantry fighting vehicles in a very similar role, but the latter has some capabilities lacking in the former.
Successful general-purpose armoured fighting vehicles often also serve as the base of a whole family of specialised vehicles, for example, the M113 and MT-LB tracked carriers, and the Mowag Piranha wheeled AFV.
The tank is an all terrain, armoured fighting vehicle, designed primarily to engage enemy forces by the use of direct fire in the frontal assault role. Though several configurations have been tried, particularly in the early experimental days of tank development, a standard, mature design configuration has since emerged to a generally accepted pattern. This features a main artillery gun, mounted in a fully rotating turret atop a tracked automotive hull, with various additional machine guns throughout.
Philosophically, the tank is, by its very nature, a purely offensive weapon. Being a protective encasement with at least one gun position, it is essentially a pill box or small fortress, (though these are static fortifications of a purely defensive nature) that can move toward the enemy - hence its offensive utility.
Historically, tanks are divided into 3 categories: Light Tanks (small, thinly armoured, weakly gunned, but highly mobile tanks intended for the armoured reconnaissance role) Medium Tanks (mid-sized, adequately armoured, respectably gunned, fairly mobile tanks intended to provide an optimum balance of characteristics for manoeuver combat, primarily against other tanks) Heavy Tanks (large, thickly armoured, powerfully gunned, but barely mobile tanks intended for the breakthrough role against fortified lines, particularly in support of infantry formations) Other designations (such as Cavalry Tank, Cruiser Tank, Infantry Tank) have been used by various countries to denote similar roles.
A modern main battle tank incorporates advances in automotive, artillery, and armour technology to combine the best characteristics of all three historic types into a single, all around type. It is distinguished by its high level of firepower, mobility and armour protection relative to other vehicles of its era. It can cross comparatively rough terrain at high speeds, but is fuel, maintenance, and ammunition-hungry which makes it logistically demanding. It has the heaviest armour of any vehicle on the battlefield, and carries a powerful weapon that may be able to engage a wide variety of ground targets. It is among the most versatile and fearsome weapons on the battlefield, valued for its shock action against other troops and high survivability.
Armoured personnel carriers (APCs) are light armoured fighting vehicles for the transport of infantry. They usually have only a machine gun although variants carry recoilless rifles, anti-tank guided missiles (ATGMs), or mortars. They are not really designed to take part in a direct-fire battle, but to carry the troops to the battlefield safe from shrapnel and ambush. They may have wheels, tracks, or both as in the half-track. Examples include the American M113 (tracked), the British FV 432 (tracked), the Dutch/German Boxer MRAV (wheeled), the French VAB (wheeled), the Soviet BTR (wheeled), and the American M3 (half-tracked).
The first attempt to carry troops in an armoured tracked vehicle was made by the British in the First World War, a lengthened Mark V* tank that could house a squad of infantry while still armed as a tank. Post-war, the idea was largely dropped in favour of trucks, small infantry carriers, and lightly-armoured half-tracks, which were widely used during the Second World War. During WWII there were some experiments into heavily armoured carriers, such as the Kangaroos, converted by stripping turrets from tanks. After the war, there was a shift away from half-tracks to tracked or wheeled armoured personnel carriers (APCs), usually armed with a machine gun for self-defence. A new one, currently being built for the Israeli Defence Forces is the Wolf.
Infantry Mobility Vehicle (IMV) is a modern term for a wheeled armoured personnel carrier (APC) which serves as a military patrol, reconnaissance or security vehicle. The distinction between it and an armoured car being the ability to carry a unit of infantry. Modern examples include the ATF Dingo, Bushmaster IMV, Stryker Infantry Carrier Vehicle (ICV) and vehicles being fielded as part of the MRAP program.
An infantry fighting vehicle (IFV) is an armoured personnel carrier which allows the infantry to fight from inside, and can provide significant fire support. The first IFV was the Soviet BMP-1, which surprised the western intelligence analysts when it appeared in a military parade in 1967.
Modern IFVs are well-armed infantry carriers that allow the infantry inside to fight from within the vehicle. They are different from earlier APCs by their heavier armament allowing them to give direct-fire support during an assault, firing ports allowing the infantry to fire personal weapons while mounted, and improved armour. They are typically armed with a twenty millimetre or larger autocannon, and possibly with ATGMs. IFVs are usually tracked, but some wheeled vehicles fall into this category, too.
Specially-equipped IFVs have taken on some of the roles of light tanks; they are used by reconnaissance organizations, and light IFVs are used by airborne units which must be able to fight without the heavy firepower of tanks.
By comparison the Israeli Merkava is a main battle tank with the ability to carry a section of infantry.
Self-propelled artillery are artillery pieces which have been given their own integral transport by mounting them on tracked or wheeled chassis. They are usually armoured as well. The mobility provided allows artillery to keep up with the pace of armoured warfare, and gives them nominal protection from counter-battery or small arms fire. Like towed artillery, a battery of self-propelled guns must still set up in a relatively safe area to perform fire missions, but is able to relocate more quickly.
Assault guns are self-propelled artillery pieces intended to support infantry in the direct-fire role. They usually have a large-calibre gun capable of firing a heavy high-explosive shell, effective against dug-in troops and fortifications.
Self-propelled anti-tank guns, or tank destroyers, are used primarily to provide antitank support for infantry or tank units, in defensive or withdrawal operations. They may mount a high-velocity anti-tank gun or sometimes an antitank guided missile launcher, or ATGM.
Tank destroyers cannot fulfill the many roles of tanks; they are much less flexible, and usually lacking in anti-infantry capability, but they are much less expensive to manufacture, maintain, and resupply than tanks.
Gun-armed tank destroyers have been largely supplanted by the more general-purpose tanks and ATGM launchers since Second World War, with lightly-armoured ATGM carriers used for supplementary long-range antitank capabilities, and to replace tanks in light or airborne forces.
A tankette is a small armoured fighting vehicle with a crew of one or two, similar to a tank, intended for infantry support or reconnaissance. Most had no turret and were armed with one or two machine guns, or rarely with a heavier gun or grenade launcher. Tankettes were produced between about 1930 and 1941, but the concept was abandoned because of its limited utility and vulnerability to anti-tank weapons. Their role was largely taken over by armoured cars.
A classic design was the British Carden Loyd tankette—many others were modelled after it. Japan was among the most prolific users of tankettes, producing a number of designs, which they found useful for jungle warfare.