Infantry tank

The infantry tank was a concept developed by the British and French in the years leading up to World War II. Infantry tanks were tanks designed to support the infantry in the attack. To achieve this they were generally heavily armoured compared to the cruiser tanks, to allow them to operate in close concert with infantry even under heavy gun fire. The extra armouring came at the expense of speed, which was not an issue when supporting relatively slow moving infantry.

Once the infantry tank-supported attack had broken through heavily defended areas in the enemy lines, other tanks such as cruisers, or light tanks, were expected to exploit their higher speed and longer range to operate far behind the front in order to cut lines of supply and communications.

Background
The split between the infantry tank and cruisers had its origins in the World War I division between the first British heavy tanks and the faster Whippet Medium Mark A and its successors the Medium Mark B and Medium Mark C.

During the interbellum British tank experiments generally followed these basic classifications, which were made part of the overall doctrine with the work of Percy Hobart and Captain B.H. Liddell Hart.

Comparisons to other tank types
Using later terminology, the infantry tank has been compared to a heavy tank, while the cruisers were compared to mediums, lights, or even armoured cars. This comparison can be misleading though: particularly as the infantry tank was never intended to have the same anti-tank capabilities as a heavy tank.

The infantry tank was distinctly different from either the "heavy tank" or "breakthrough tank" concepts, although some pre-war multi-turreted heavy tanks such as the Soviet T-35 and German Neubaufahrzeug (both taking some of their inspiration from the Vickers A1E1 Independent tank prototype - an idea which was abandoned by the War office in the late 1920s for lack of funding) were similar, and with similar doctrines for their use. The Neubaufahrzeug was considered too slow for Blitzkrieg tactics and fell from favour. German (and to some extent Soviet) wartime doctrine shifted towards faster medium and heavy tanks fighting large multi-tank battles, with the role of the infantry tank in assaults taken by simpler self-propelled artillery.

An important difference, however, was that heavy tanks were generally very well armed, while infantry tanks were not necessarily better-armed than other tanks. For example, the Soviet KV-1 heavy tank and British Matilda infantry tank were deployed at about the same time in 1940. These two tanks had similar levels of armour protection and mobility, but the KV was far more heavily armed than the Matilda.

In British practice, the main armament of the infantry tank went in three phases. The pre-Dunkirk British Army Matilda I had only a single machine gun, a compromise forced by the lightness of its chassis. The Matilda II gained a capable anti-tank capacity for its time, with the 40mm 2 pounder, but these were only issued with solid-shot (i.e. non-explosive) for anti-tank use and was of little use for artillery close-support of infantry. The ultimate evolution of the British infantry tank concept began with the Churchill MkI, where a hull-mounted 3 inch howitzer could support infantry assaults with HE shells. As the increasing size of tanks, and their turret ring diameters, allowed such a howitzer to be turret-mounted in vehicles such as the Crusader CS & Centaur CS.

UK
Since the infantry tanks were to work at the pace of the infantry units, which would be attacking on foot, high speed was not a requirement and they were able to carry heavier armour. The first two purpose-designed infantry tanks, the Mark I "Matilda" and Mark II "Matilda" were armed with a heavy machine gun and QF 2 pounder anti-tank gun respectively. These two saw action in the Battle of France.

They were followed by the Valentine and Churchill designs. The Valentine proved to be difficult to develop further but the Churchill went through successive variants and served up to the end of the war.

As British cruiser tank designs developed into larger tanks with more powerful engines, they could carry larger guns and more armour yet still achieved high speeds. At the end of the war the cruiser tank lineage led to the "universal tank" in the form of the Centurion.

In practice the British did not operate only infantry and cruiser tanks. Lack of production capacity meant the large scale adoption of US medium tanks.

France
In the French Army the infantry tank role was filled largely by the Renault R35, a light tank, which was similar to the Matilda I in terms of armour, but better armed.

In practice, although able to resist hits from tanks and anti-tank guns, and designed for good, albeit slow, cross-country performance, the separation of tank functions into specialised areas such as infantry and cruiser types was not effective. Invariably the cruisers ended up meeting enemy tanks in combat, while the infantry tanks were the only ones present when a breakthrough was accomplished. The infantry tank idea faded as tank design progressed during the war. It was eventually replaced outright with the general acceptance of the universal tank idea.

The concept was also employed by the other big tank-producing nation of the 1930s: the Soviet Union, as exemplified by the T-26 tank. The T-26 was a light tank assigned to Infantry units and thus fulfilled the infantry tank role, but in it had the relatively thin armour of light tank, but with a potent 45 mm gun. Their BT tanks were the fast cruiser types.

Germany had its separate Panzerwaffe and the German Infantry used phased out Panzerkampfwagen I's in its Independent Tank Brigades. This is often seen as reflecting some explicit doctrine; in reality it was caused by a simple lack of budget, tank production not having any priority. When more money became available the Sturmgeschütz III was taken into use by the Artillery, in its original role of infantry close support vehicle - the counterpart of the allied Infantry tanks.

Despite the concept of splitting of tanks into infantry and cruiser roles being an instance of the general economic principle of division of labour in mechanization, during World War II its application in mechanized warfare proved to be hugely inefficient in terms of technical development, production, maintenance, logistics, and — worst of all — tactical flexibility. Therefore it was not surprising that during the war, it was progressively abandoned by all the major belligerent countries.

US
For political reasons, the US Army was not permitted "tanks" in the years before WWII and so the tracked AFVs that it did develop were termed "Combat Cars" instead. This attitude, and their deployment with cavalry units, encouraged their treatment as light tanks. When the first medium tank design appeared, it was a confused design that had some features of the already outdated multi-turret designs: multi machine-gun mounts, light anti-tank weapon, but omitted the close-support howitzer that was by now an important feature of British and French designs.