| Mark IV | |
|---|---|
 Mark IV male withunditching beam deployed | |
| Type | Heavy tank |
| Place of origin | United Kingdom |
| Service history | |
| Used by | British Army Imperial German Army Reichswehr Imperial Japanese Army |
| Wars | First World War German Revolution of 1918–19 |
| Production history | |
| Designer | |
| Manufacturer | see text |
| Unit cost | about £5,000[1] |
| Produced | May 1917 – end 1918 |
| No. built | 1,220 |
| Specifications | |
| Mass | 28tons (28.4 tonnes) Female: 27 tons (27.4 tonnes) |
| Length | 26 ft 5 in (8.05 m) |
| Width | Male: 13 ft 6 in (4.12 m) |
| Crew | 8 |
| Armour | 0.5 inches (12 mm) |
Main armament | Male: Two6-pounder (57-mm) 6 cwt QF guns with 332 rounds Female: five.303Lewis guns |
Secondary armament | Male: Three .303 in Lewis guns |
| Engine | Daimler-Foster, 6-cylinder in-linesleeve valve 16 litre petrol engine 105 bhp at 1,000 rpm |
| Transmission | Primary: 2 Forward, 1 Reverse Secondary – 2 speed |
| Fuel capacity | 70Imperial gallons |
Operational range | 35 mi (56 km) |
| Maximum speed | 4 mph (6.4 km/h) |
TheMark IV (pronouncedMark four) was a Britishtank of theFirst World War. Introduced in 1917, it benefited from significant developments of theMark I tank (the intervening designs being small batches used for training). The main improvements were inarmour, the re-siting of the fuel tank and ease of transport. Armour was increased to resist the German armour-piercing bullet, the drivetrain was strengthened and side turrets were constructed so that they could be swung inside, enabling travel by train (Previously they had to be separately transported to the battlefield by truck).[2] A total of 1,220 Mark IVs were built: 420"Males", 595"Females" and 205 Tank Tenders (unarmed vehicles used to carry supplies), which made it the most numerous British tank of the war. The Mark IV was first used in mid 1917 at theBattle of Messines Ridge. It remained in British service until the end of the war, and a small number served briefly with other combatants afterwards.
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 use of the Mark II and III as interim training tanks. Failing to complete development soon enough to start production in time to have 200 tanks ready for the promised date of 1 April 1917, Stern was ultimately forced to take a Mark IV into production in May 1917 that was only slightly different from theMark I tank.
The Mark IV Male initially carried threeLewis machine guns – one in the cab front and one in eachsponson[nb 1] – and aQF 6 pdr 6 cwt gun in each sponson, with its barrel shortened as it had been found that the longer original was apt to strike obstacles or dig into the ground. The sponsons were not mirror images of each other, as their configuration differed to allow for the 6 pdr's gun-layer operating his gun from the left and the loader serving the gun from the right. The guns had a 100 degreearc of fire but only the starboard gun could fire straight ahead.[3] The Female had five Lewis guns but no 6-pounders.
The decision to standardise on the Lewis gun was due to the space available within the tanks. Despite its vulnerable barrel and a tendency to overheat or foul after prolonged firing, the Lewis had the advantage that it used compactpan magazines which could hold up to 96 rounds. TheHotchkiss was fed from a rigid strip which was trimmed down to only 14 rounds for tank use; no sooner had the machine gunner guided the fall of shot onto the target than it was time to change the strip and the process repeated.[4] It was not until a flexible 50 round strip was fully developed in May 1917 that the Hotchkiss would become the standard machine gun for tanks again. The changes caused delays, such as adapting the design for the bulky Lewis cooling barrel, and later, problems when the Hotchkiss strips had to be stored in positions designed for Lewis gun magazines.[4]
At the 1917Battle of Cambrai, Mark IV tanks were equipped withfascines, bundles of brushwood bound with chains, about 10 ft (3.0 m) long and 4 ft 6 in (1.37 m) in diameter carried on the roof of the cab. They were dropped into trenches to allow the tank to cross over more easily.[5]
A large number of these tanks were also used for development work. In an attempt to improve trench-crossing capability, the "tadpole tail", an extension to the rear track horns, was introduced. However, it proved insufficiently rigid and does not appear to have been used in combat. Other experimental versions tested radios, mortars placed between the rear horns, and recovery cranes. Some of these devices were later used on operational tanks. Mark IVs were also the first tanks fitted with "unditching beams" by field workshops. A large wooden beam, reinforced with sheet metal, was stored across the top of the tank on a set of parallel rails. If the tank became stuck, the beam was attached to the tracks (often under fire) and then the tracks would drag it beneath the vehicle, providing grip.
The Mark IV was built by six manufacturers:Metropolitan (the majority builder),Fosters of Lincoln,Armstrong-Whitworth,Coventry Ordnance Works,William Beardmore & Company andMirrlees, Watson & Co., with the main production being in 1917. The first order was placed for 1,000 tanks with Metropolitan in August 1916. It was then cancelled, reinstated and then modified between August and December 1916. The other manufacturers, contracted for no more than 100 tanks each, were largely immune to the conflict between Stern and the War Office.[6]
The Mark IV was first used in large numbers on 7 June 1917, during the British assault onMessines Ridge. Crossing dry but heavily cratered terrain, many of the 60-plus Mark IVs lagged behind the infantry, but several made important contributions to the battle. By comparison, at theThird Battle of Ypres (also known as Passchendaele) from 31 July, where the preliminary 24-day long barrage had destroyed all drainage and heavy rain had soaked the field, the tanks found it heavy going andcontributed little; those that sank into the swampy ground were immobilised and became easy targets for enemy artillery.[7]
Nearly 460 Mark IV tanks were used during theBattle of Cambrai in November 1917, showing that a large concentration of tanks could quickly overcome even the most sophisticated trench systems.
In the aftermath of theGerman spring offensive on the Western Front, the first tank-to-tank battle was between Mk IV tanks and GermanA7Vs in theSecond Battle of Villers-Bretonneux in April 1918.[nb 2]
About 40 captured Mark IVs were employed by the Germans asBeutepanzerwagen (the German wordBeute means "loot" or "booty") with a crew of 12.[8] These formed four tank companies from December 1917.[9] Some of these had their six pounders replaced by a German equivalent.[10]
The last Mark IV to see service, briefly, wasExcellent, a Mark IV male retained by the naval gunnery schoolHMSExcellent onWhale Island in Portsmouth harbour. In 1940 it was restored to operational status and driven to the mainland, where its new career was allegedly brought to an early end after damaging a car.[11]
Tanks of theFirst World War | |
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| Light | |
| Medium | |
| Heavy | |
| Prototypes, experimentals | |
Britisharmoured fighting vehicles of theFirst World War | |||||||||
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| Tanks |
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| Armoured cars | |||||||||
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