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The Light Tank Mk VII (A17), also known as the Tetrarch, was a British light tank produced by Vickers-Armstrongs in the late 1930s and deployed during the Second World War. The Tetrarch was originally designed as the latest in the line of light tanks built by the company for the British Army. It improved upon its predecessor, the Mk VIB Light Tank, by introducing the extra firepower of a 2-pounder gun. The War Office ordered 70 tanks, an order that eventually increased to 220. Production was delayed by several factors, and as a consequence, only 100 to 177 of the tanks were produced.〔Tucker (p. 90) states that 177 of the Mk VII's were built during the war, but Flint (p. 12) states that whilst this figure is given in most published sources, surviving War Office documentation gives a lower figure of 100, putting the final tally somewhere between these two figures〕 The tank's design flaws, combined with the decision by the War Office not to use light tanks in British armoured divisions, ruled out the use of Tetrarchs in the North African Campaign. As a result, the majority of the tanks remained in Britain, although 20 were sent to the USSR as part of the Lend-Lease program. In early 1941, the Royal Armoured Corps formed three squadrons for use in overseas amphibious operations, one of which was equipped with Tetrarchs. In May 1942, a small number of Tetrarchs formed part of the British force which participated in the invasion of Madagascar, and, in June 1942, Tetrarchs were attached to the 1st Airborne Division after it was decided that the design allowed its use as an air-portable light tank to support British airborne forces. The Tetrarchs were transported and landed in specially designed General Aircraft Hamilcar gliders.〔("Huge Gliders Spill Tanks Behind Enemy Lines'" ) ''Popular Mechanics'', December 1944, p.17. Note – article has two errors. One it, mistakenly states the tank loading in the Hamilcar is the American M22 Locust when in fact they are British Tetrarchs. Two, the Hamilcars landed no tanks in Operation Tonga.〕 A lack of gliders prevented their participation in the Allied invasion of Sicily in 1943; instead they were attached to the new 6th Airborne Division and became part of the 6th Airborne Armoured Reconnaissance Regiment. The division used approximately 20 Tetrarchs during the British airborne landings in Normandy in June 1944. The tanks were successfully landed by glider, but they did not perform well. Several were lost in accidents, and those that did see action proved to be inferior in firepower and armour to the armoured fighting vehicles of the German forces. A few days after the beginning of the operation, the tanks were removed from direct engagement with German armour and used only to provide fire support. By August 1944, most of the Tetrarchs in action were replaced with Cromwell cruiser tanks, and the remainder were replaced by the M22 Locust in December 1944. Tetrarchs did not see any further combat and were deemed obsolete by 1946; the last was retired in 1950. There were several variations on the Tetrarch design, including the Alecto self-propelled gun and the Light Tank Mk VIII, but none of these were ever used in active service with the British Army. ==Development history== The prototype of the Light Tank Mk VII (A17), nicknamed 'Purdah',〔Bishop, p. 24〕 was first developed in 1937 by Vickers-Armstrongs as a private venture, and was intended to be sold either to the British Army or to foreign militaries.〔Flint, p. 9〕 It was to be the latest in a series of light tanks produced by the company.〔 The tank was designed to overcome the shortcomings of insufficient armament in earlier light tanks that were fitted only with machine guns.〔Tucker, p. 89〕 Vickers-Armstrong installed on the Mk VIIs a paired with a Besa machine gun, and mounted the two guns in a two-man turret. The tank possessed a maximum of of armour.〔〔 The prototype weighed approximately and was powered by a Meadows engine. Suspension was on eight road wheels, four per side, with no separate driver or idler wheels and it was capable of a top speed.〔〔Flint, p. 11〕 The Mk VII design relied on an unusual steering method and a mechanical system incorporated into earlier Vickers models.〔Chamberlain & Ellis, p. 26.〕 The front wheels could be steered to allow for gentle turns by bending the tracks. For sharper turns, the system returned to the conventional method of braking one track to turn the tank; the dual system of turning was designed to lessen mechanical strain on the MkVII and reduce its power wastage.〔〔〔Flint, p. 10〕 The suspension system was also a new design that relied on struts with pockets of air for springing and cushions of oil for damping, and each of the wheels was independently sprung.〔 The War Office examined the design and put the prototype through a series of trials during May and June 1938; the model was tested as a possible "light cruiser" since War Office light tank needs were already met by its predecessor, the Mark VI.〔 The War Office then took the view that the tank was not acceptable as a light cruiser because the Nuffield A13 offered better speed and obstacle crossing performance.〔Foss & McKenzie, pp. 95–97〕 Despite this, it was decided that it was essential for some Tetrarchs to be produced, and it was suggested that they be brought in at the end of the light tank program.〔 Accordingly, the War Office gave the Tetrarch the official General Staff specification number A17, and, in November 1938, accepted it for limited production after requesting a few minor changes which included the fitting of an external fuel tank to increase the tank's range.〔 The number to be produced was subject to fluctuation as the War Office vacillated in their demand; in July 1938, it requested that 70 of the tanks be produced, then increased the request to 120 after a three-day conference in November. Production was to begin in July 1940, but meanwhile the War Office temporarily returned to its original order of 70 before increasing the number to 100. The number further increased to 220 after Metropolitan Cammell Carriage and Wagon, a company part owned by Vickers-Armstrong that would be producing the tanks, indicated it had already ordered armour plating for that many tanks.〔〔Tucker, pp. 89–90〕 Production of the tank was delayed by a number of factors. The War Office put their order on hold in a post-Battle of France decision to focus military production on infantry and cruiser tanks,〔Tucker, p. 90〕 due to the poor performance of British light tanks during that battle. Due to the shortage of more suitable tanks, light tanks that were not designed for use against German armour, were nevertheless deployed against them; the resulting high casualties led the War Office to re-evaluate the suitability of the light tank design.〔 The pre-war role of the light tank, that of reconnaissance, meanwhile had been found to be better suited to scout cars that used smaller crews and had better cross-country abilities.〔〔 Further delays were caused by the bombing raids of the ''Luftwaffe'' during May 1941 against the factories where the tanks were assembled.〔Fletcher, Part 1, p. 42〕 These delays resulted in the production of only a small number of Mk VIIs; estimates place the final total produced to be between 100 and 177. The name 'Tetrarch' was given to the Mk VII, on 22 September 1941, on the orders of the War Office. The last of the tanks were built in the first quarter of 1942 and delivered at the end of the year.〔 The War Office and the Army were concluding, at this point, that light tanks were a liability and too vulnerable for use in further combat,〔 and the Tetrarch was considered to be obsolete.〔Flint, p. 16〕 This decision may have marked the end for the Tetrarch in active service; several of the tanks destined to be deployed to the Eighth Army in the Middle East for the North African Campaign were left in Britain when their cooling systems were determined to be unable to cope with the intense North African heat.〔Flint, p. 13〕 However, the demise of Tetrarch was prevented by a decision made by the War Office in mid-1941, as it was considering the equipment to be used by Britain's fledgling airborne forces, formed in June 1940 under the orders of the Prime Minister, Winston Churchill.〔Otway, p, 21〕 When selecting the equipment for the airborne forces, officials at the War Office concluded that gliders would be an integral component; gliders would transport troops and heavy equipment, which, by 1941, was to include artillery and some form of tank.〔Flint, p. 15〕 Plans to transport a tank went through a number of revisions, but, by May 1941, the feasibility of a tank to be carried for in a glider was accepted, although the aircraft would have to be specifically designed for the task. In a conference held on 16 January 1941, it was decided that the General Aircraft Hamilcar, currently under development, would be used to transport a single Tetrarch tank or two Universal Carriers.〔〔Flint, pp. 15–16〕 The Tetrarch was chosen because it was an obsolete design, and was therefore available to be used by the airborne forces.〔 Beginning in January 1944, training exercises were conducted carrying the Tetrarchs and their crews inside Hamilcar gliders. These exercises were successful; during the training by 'C' Squadron of the Glider Pilot Regiment, which specialised in flying the Hamilcars, over 2,800 lifts were made with an average of 50 lifts per crew. Only three incidents resulted in fatalities or injuries, with seven pilots killed during the training.〔Flint, p. 86〕 When the Tetrarch was re-designated as an airborne tank, several changes were made to its design. A number of tanks had their 2 pounder guns replaced with a infantry support howitzer; these tanks were then designated as Tetrarch 1 CS (Close Support). Additionally, Littlejohn adaptors were added to those Tetrarchs which still possessed their 2 pounders to increase their muzzle velocity and armour penetration.〔 The Tetrarch experienced several setbacks throughout its development and deployment with the Army and airborne forces. One of the major problems was the limited number of these tanks that existed after production ended in 1942, which particularly affected the airborne forces. The transport of 20 of the tanks to the USSR under the Lend-Lease Act depleted the number available for use by airborne forces, as did the loss of several more during Operation Ironclad, the invasion of Madagascar.〔Flint, p. 14〕 A Royal Armoured Corps report issued in December 1942 stated that approximately 50 Tetrarchs were available for use. In a memorandum, dated January 1943, by Major General George F. Hopkinson, commander of the 1st Airborne Division, Hopkinson complained that he had been informed that 70 of the tanks were available, whereas only 50 actually remained, with no reserves to replace those lost in combat.〔Flint, p. 82〕 This lack of sufficient replacement reserves, combined with a War Office report that some 287 airborne tanks would be required for the 1st Airborne Division and an unnamed airborne division to be formed in India, led to the Tetrarch's eventual replacement by the US M22 Locust.〔 抄文引用元・出典: フリー百科事典『 ウィキペディア（Wikipedia）』 ■ウィキペディアで「Light Tank Mk VII Tetrarch」の詳細全文を読む スポンサード リンク
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