The British Mark I was the world's first combat tank, entering service in the middle of World War I, born of the need to break the domination of trenches and machine guns over the battlefields of the Western Front. Along with its subsequent variants, it was the most successful heavy tank of the war.
The Mark I was a rhomboid vehicle with a low centre of gravity and long track length, able to grip muddy ground and cross trenches. Sponsons (also called "barbettes") on the hull sides carried two naval 6-pounder guns. There were two Hotchkiss machine guns in the sponsons and two removable guns for the front and back.
The hull was undivided internally; the crew shared the same space as the engine. The environment inside was extremely unpleasant; the atmosphere was contaminated with poisonous carbon monoxide, fuel and oil vapours from the engine and cordite fumes from the weapons as ventilation was inadequate. Temperatures inside could reach 50 °C (122 °F). Entire crews lost consciousness or became violently sick when again exposed to fresh air.
To counter the fumes inside and the danger of bullet splash or fragments and rivets knocked off the inside of the hull, the crew wore helmets with goggles and chainmail masks. Gas masks were standard issue as well, as they were to all soldiers at this point in the war (see Chemical warfare). The side armour of 8 mm initially made them largely immune to small arms fire, but could be penetrated by the recently developed armour-piercing K bullets. There was also the danger of being overrun by infantry and attacked with grenades. The next generation had thicker armour, making them nearly immune to the K bullets. In response, the Germans developed a larger purpose-made anti-tank rifle, and also a Geballte Ladung ("Bunched Charge")—several regular stick grenades bundled together for a much bigger explosion.
A direct hit on the roof by an artillery or mortar shell could cause the fuel tanks (which were placed high in the front horns of the track frames either side of the drivers' area, to allow gravity feed) to burst open. Incinerated crews were removed by special Salvage Companies, who also salvaged damaged tanks. They were forbidden to speak about this aspect of their work with still living tank crews.
Steering was difficult; controlled by varying the speed of the two tracks. Four of the crew, two drivers (one of which also acted as commander; he operated the brakes, the other the primary gearbox) and two "gearsmen" (one for the secondary gears of each track) were needed to control direction and speed — the latter never more than a walking pace. As the noise inside was deafening, the driver, after setting the primary gear box, communicated with the gearsmen with hand signals, first getting their attention by hitting the engine block with a heavy spanner. For slight turns, the driver could use the steering tail: an enormous contraption dragged behind the tank consisting of two large wheels, each of which could be blocked by pulling a steel cable causing the whole vehicle to slide in the same direction. If the engine stalled, the gearsmen would use the starting handle—a large crank between the engine and the gearbox. Many of these vehicles broke down in the heat of battle making them an easy target for German gunners. There was no wireless (radio); communication with command posts was by means of two pigeons, which had their own small exit hatch in the sponsons, or by runners who were encouraged to complete their suicidal mission by receiving bottles of strong drink as a reward.
Later marks carried semaphore arms for signalling.
To aid steering, a pair of large wheels were added behind the tank. These were not as effective as hoped and were subsequently dropped.
The subsequent Mark II, III, IV and V and later tanks all bear a strong resemblance to their "Mother".
The Gun Carrier Mark I was largely produced with parts identical to those used to build the Mark I.
Unhardened armour. Built from December 1916 to January 1917 for training only, but used in the Battle of Arras in April 1917 because of delays in the production of the Mark I tank.
The Mark III was a training tank, which used Lewis machine guns and a smaller sponson for the females. Fifty were built. It was originally intended that the Mark III have all the proposed new design features of the Mark IV. This is why there were two distinct training types, the Mark II being little more than a slightly improved Mark I. Development of the new features was so slow however, that the change from the Mark II was very gradual only. The last two Mark III's were melted down in World War II.
The director of the Tank Supply Department, Albert Gerald Stern, first intended to fit the Mark IV with a new engine and transmission. Production of battle tanks was halted until the new design was ready, necessitating the Mark II and III as interim training tanks. He failed however to complete development soon enough to start production in time to have 200 tanks ready for the promised date of 1 April 1917. He was ultimately forced to take a Mark IV in production in May 1917 that was only slightly different from the Mark I.
The Mark IV Male carried four Lewis machine guns as well as the two sponson guns (now QF 6 pdr 6 cwt with shorter barrels). The Female had six machine guns. Two of the machine guns were operated by the gun loaders.
The Mark V was first to be a completely new design. When however in December 1917 the desired new engine and transmission became available, this design was abandoned and the designation switched to an improved version of the Mark IV, in fact a Mark IV as it was originally intended: more power (150 bhp) with a new Ricardo engine, improved steering mechanism and epicyclical transmission, only one driver was needed. Cabin for machine-gunner on the roof. Four hundred were built, 200 each of Males and Females. Several were converted to Hermaphrodites by swapping sponsons to give a single 6 pounder gun for each. These are also sometimes known as "Mark V Composite".
Sir William Tritton in 1917 developed the Tadpole Tail: an extension of the tracks to be fitted to the back of a tank to improve trench crossing abilities. This was necessary because the Hindenburg Line had 3.5 metre wide trenches to stop the British tanks. When Major Philip Johnson of Central Tank Corps Workshops heard of this project, he immediately understood that the weight of the heavy girders strengthening the attachment might be put to a better use by creating a larger tank. He cut a Mark IV in half and stretched the hull, lengthening it by six feet. When details had been forgotten it has for a long time been assumed that most Mark V* had been field conversions made by Johnson. We now know that they were all factory-built. It had a larger "turret" on the roof and doors in the side of the hull. The weight was 33 tons. 645 were built out of an order for 500 Males and 200 Females.
The extra section was also designed to house a squad of infantry. This was the first ever purpose designed tracked armoured personnel carrier (APC), it was also the first APC to be significantly armed, as some earlier conversions of tanks into supply carriers lacked any armament. It could operate as a tank as well as carrying troops, and it was not until the post World War II era Merkava that a tank that could also carry troops under protection was produced.
Note: the asterisk (*) in early British tank designations was usually pronounced as "star" when spoken, e.g., Mark Five-star, or Mark Five-star-star, etc.
Because the Mark V* had been lengthened, its original length-width ratio had been spoiled. Lateral forces in a turn now became unacceptably high causing thrown tracks and an enormous turn circle. Therefore Major Wilson redesigned the track in May 1918, with a stronger curve reducing ground contact (but increasing ground pressure as a trade-off). An uprated 225 hp Ricardo engine was fitted. The cabin for the driver was combined with the roof cabin; there now was a separate machine gun position in the back. 197 were built out of an order for 750 Males and 150 Females.
American involvement in the development of the tank design led to the Mark VIII, also known as "Liberty" or Anglo-American tank (though initially the French were partially involved).
The engine was compartmentalised from the crew, and the turret structure included forward and rear firing machine guns. Of a planned (shared production) of 1,500 each, 24 were built by the British before they pulled out of the project and 100 completed by the Americans. The 100 were produced between September 1918–1920, at the Rock Island Arsenal, at a cost of $35,000 apiece ($430,000 in 2006).
They were used and upgraded until the 1930s when given to Canada for training (as opposed to the M1917s which were sold at scrap value). The tank itself was over 34 feet (10 m) long, and there had been an even longer 44 foot (13 m) version planned but never made (the Mark VIII*). The tank was outdated by the 1930s due to its speed (under 6 mph/10 km/h) and armour (16–6 mm) but it did have one of the longest independent trench crossing capabilities of any armoured fighting vehicle (AFV) ever made. Modern main battle tanks and AFVs rely on bridge laying tanks for crossing large deep trenches.
The Mark IX was a troop carrier or infantry supply vehicle—among the first tracked armoured personnel carrier not counting experiments with the lengthened Mk V's. 34 were built out of an order for 200.
The first tanks were added, as "Heavy Branch", to the Machine Gun Corps until a separate Tank Corps was formed on 28 July 1917 by Royal Warrant. A small number of Mark I tanks took part in the battle of the Somme during the Battle of Flers-Courcelette in September 1916. Although many broke down or became stuck, almost a third that attacked made it across no mans land, and their effect on the enemy was noted leading to a request by the British C-in-C Douglas Haig for a thousand more. This came as a bit of a surprise: William Tritton had already started the development of a heavier tank: the Flying Elephant. Unfortunately for the Allies, it also gave the Germans time to develop a specifically designed anti-tank weapon for the infantry, an armour-piercing 7.92 mm bullet.
Mark IV tanks were used at the Third Battle of Ypres (Passchendaele) in mid-1917, but without great success due to the mud. Nearly 460 Mark IV tanks were used during the Battle of Cambrai in November 1917, showing that a large concentration of tanks could quickly overcome even the most sophisticated trench system. About forty captured Mark IVs were employed by the Germans as Beutepanzer with a crew of twelve. (The German word Beute means "loot" or "booty".) Some of these had their six pounders replaced by a German equivalents..
In the aftermath of the German Spring Offensive on the western front, the first tank-to-tank battle was between Mk IV tanks and German A7Vs in the Second Battle of Villers-Bretonneux in April 1918,(see that entry for details). During the Battle of Amiens in August 1918, several hundred Mark V tanks with the new Whippet tank penetrated the German lines in a foretaste of modern armoured warfare.
Mark V and Whippet tanks were supplied by the British to the White movement during the Russian Civil War; some were subsequently captured by the Red Army. When some White Russian forces fell back, their tanks were taken on by the Estonians and used until 1941. Mark Vs were also delivered to the French, Canadian and American army.
A Mark V tank can be seen in several photographs taken in Berlin in 1945 in front of the Berliner Dom (Berlin Cathedral). It has been suggested this was a museum piece that had been previously displayed at the Lustgarten and it had been used as a static pillbox to help bolster the city's defences during Nazi Germany's final days. However, there is no evidence this was the case and it is not clear what role (if any) it played in the Battle of Berlin.
Seven Mark IV's survive.
Eleven Mark V's survive. The majority are in Russia or the Ukraine and are survivors of the tanks sent there to aid the White forces during the Russian Civil War.