|This article does not cite any sources. (January 2011)|
Soviet IS-3 heavy tank
|In service||1917 – ca. 1990s|
A heavy tank was a subset of tank that provided equal or greater firepower as well as armor than tanks of lighter classes, at the cost of mobility and maneuverability and, particularly, expense.
The origins of the class date to World War I and the very first tanks; designed to operate in close concert with the infantry and facing both artillery and the first dedicated anti-tank guns, early tanks had to have enough armor to allow them to survive on no man's land. As lighter tanks were introduced, the larger designs became known as heavies. The same basic role remained into World War II, with the British referring to them as infantry tank indicating this close support role.
As tank combat became more common, especially tank-vs-tank, the heavies also became platforms to mount very powerful anti-tank guns, and the role of the heavies began to change. By the end of the war they were a primary class, used both for dealing with heavy fortifications as well as forcing its way through enemy tank formations. They were also known as breakthrough tanks, indicating their purpose of spearheading the attack. In spite of this, in practice they have been more useful in the defensive role than in the attack.
The emergence of the main battle tank spelled the end of the heavy tank as a separate class, although a number of post-war examples were produced. These were generally gone by the 1960s.
Line between heavy and medium tanks
There was not a consistent line distinguishing heavy tank from medium tanks. The definition only became apparent during the interwar/war period, when the Germans adopted the "blitzkrieg" method of warfare and the heavy tanks, mostly infantry tanks at the time, were too slow to keep up, and where light tanks (or cruiser tanks) were not sufficiently armored. Ultimately the line was drawn by a vehicles weight in conjunction with its operational capability, particulairly its armament.
Heavy tanks achieved their greatest successes both fighting other, lighter tanks, and destroying fortifications with their very large guns. Although it is often assumed that heavy tanks suffered inferior mobility to mediums, this was not always the case, as many of the more sophisticated heavy tank designs featured advanced suspension and transmission precisely to counteract this drawback. But the greatest drawback is cost which translates into production quantities and/or design. The German Tiger I, for example, had similar speed and better terrain-handling characteristics when compared to the significantly lighter Panzer IV medium tank, albeit at the cost of low reliability and only 1,355 were produced compared to 8,800 Panzer IV and 84,070 Soviet T-34 and 40,000 American M4 Sherman medium tanks. This case repeated itself in the operational use of the Tiger II of which only 492 were produced.
Heavy tanks feature very heavy armour and weapons relative to lighter tanks. Many heavy tanks were based on lighter tanks or shared components from them; for instance, the American M103 shared many components with the lighter Patton tanks including its transmission and engine. As a result they tend to be either underpowered and comparatively slow, or have engine and drive train reliability problems. In case of an entirely new design development, which was the case with the German Tiger I, the design became needlessly complex and costly, resulting on poor production counts. Heavy tanks tend to have excellent protection and superior firepower to their lighter counterparts.
The heavy tank concept originated in World War I and coexisted with light and medium tanks until the end of the Cold War with the introduction of the main battle tank.
The first British tank, the Mark I of World War I, was introduced to break through the German defensive lines of trenches and barbed wire. When a lighter faster tank was introduced this was designated "Medium Mark A" (and known as Whippet) and the larger tanks known as "heavies".
The Char 2C was one of the largest tanks ever produced. At the start of World War II, the French and the Soviets were the only countries to have inventories of heavy tanks, such as the Char B1, T-35, and KV-1. The Matilda II infantry tank, though not weighing as much as the others,[clarification needed] was designed to the British infantry tank concept and had thicker armour than most tanks in service at the time. Later war examples were the German Tiger I and II, as well as the Soviet IS series. Note that "heavy" versus "medium" is more a question of tactical roles than weight; the Panther, for example, was a "medium" tank that outweighed most Allied "heavy" tanks.
American forces rarely fielded heavy tanks, as they still held on to the Infantry-support doctrine like the British. The US instead preferred to use tank destroyers for anti-tank combat. Also their M4 Sherman medium tanks were outclassed in terms of armor and weapons by most all heavy tanks. Near the end of WWII, the M26 Pershing is the closest the Americans had for a heavy tank, with the T-29 Heavy Tank not being completed in time to counteract the German Tiger II's.
The immediate post-war period saw the final fielding of heavy tanks, including the US M103 heavy tank, the British FV214 Conqueror, and the French ARL 44, all in response to the Soviet heavy tanks of the period. The largest tank guns were approaching maximum calibre whose shell could still be handled by the crew, even using awkward two-part ammunition (separate projectile and propellant case, similar to battleship guns), which greatly slowed their rate of fire. Thanks to improved gun designs and fire control technology, postwar medium tanks were catching up to heavy tanks in firepower. The tactical value of heavy tanks thus declined to the point that no new designs were fielded; the heavily armed mediums came to be known as the main battle tank (MBT). Doctrine held that less expensive self-propelled artillery could serve in the infantry support role. The weight of MBTs quickly increased during the Cold War, and most third generation MBTs including the M1 Abrams, Challenger 2, Leopard 2, Merkava, Arjun MBT, and Type 99 have weights similar to those of 1950s heavy tanks.
Older heavy tanks with steel armour were rendered obsolete by anti-tank guided missiles and high explosive anti-tank (HEAT) ammunition. The much more flexible missiles are effective at ranges beyond a tank gun's range, and sheer armour mass was no longer a guarantee of survivability against the largest HEAT warheads of tank guns or missiles.