Question: The main battle tank that Centurion ARV Mk II was based on was used introduced in what year?

full_context: Document 1: Cruiser Mk IV: The Cruiser tank Mk IV (A13 Mk II) was a British cruiser tank of the Second World War. It followed directly on from the Tank, Cruiser, Mk III (A13 Mk I). The first Mk IVs were Mk IIIs with extra armour fitted to the turret. Later Mk IVAs were built with the complete extra armour. The tank was used in France in 1940 and in the early part of the war in North Africa, before being withdrawn from service.
Document 2: Leopard 2: The Leopard 2 is a main battle tank developed by Krauss-Maffei in the 1970s for the West German Army. The tank first entered service in 1979 and succeeded the earlier Leopard 1 as the main battle tank of the German Army. Various versions have served in the armed forces of Germany and 12 other European countries, as well as several non-European nations, including Canada (Leopard 2A4m can), Chile, Indonesia, Singapore and Turkey. The Leopard 2 was used in Kosovo with the German Army and has also seen action in Afghanistan with the Danish and Canadian contributions to the International Security Assistance Force, as well as seeing action in Syria with the Turkish Armed Forces against IS and the YPJ.
Document 3: FV105 Sultan: FV105 Sultan is a British Army command and control vehicle based on the CVR(T) platform. It has a higher roof than the APC variants, providing a more comfortable "office space" inside. This contains a large vertical map board and desk along one side, with a bench seat for three people facing it. Forward of this are positions for the radio operator, with provision for four radios, and vehicle commander, whose seat can be raised to give him access to the pintle-mounted G.P.M.G. The driver sits forward of this in a small compartment beside the engine space, on a chair with a spring-loaded seat that allows him to recline inside the vehicle or sit upright with his head out of the hatch.
Document 4: Cromwell tank: The Cromwell tank, officially Tank, Cruiser, Mk VIII, Cromwell (A27M), was one of the series of cruiser tanks fielded by Britain in the Second World War. Named after the English Civil War leader Oliver Cromwell, the Cromwell was the first tank put into service by the British to combine high speed from a powerful and reliable engine (the Rolls-Royce Meteor), and reasonable armour. However the originally proposed dual-purpose high velocity gun could not be fitted in the turret and the medium velocity dual purpose gun fitted proved inadequate. An improved version with a high velocity gun became the Comet tank.
Document 5: Leyland 4-tonne truck: The Leyland 4-tonne truck was produced by Leyland Trucks in Lancashire. It was developed for the British Army and won the competition to replace a fleet of older Bedford M-type 4-tonne trucks. It shares some key components with the commercial 45 Series light truck. Deliveries to the British Army started in 1990. The official British Army Out of Service Date for this truck was the end of 2014, but around 650 were retained. Small numbers were exported.<ref name="Leyland Trucks (4 × 4) 4,000/5,000 kg truck"> </ref>
Document 6: Comet (tank): The Comet tank or Tank, Cruiser, Comet I (A34) was a British cruiser tank that first saw use near the end of the Second World War. It was designed as an improvement on the earlier Cromwell tank, mounting the new 77 mm HV gun in a new lower profile and part-cast turret. This gun was effective against late war German tanks, including the Panther and, at most ranges, the Tiger. The tank was widely respected as one of the best British tanks of the war, and continued in service afterwards.
Document 7: Mark V tank: The British Mark V tank was an upgraded version of the Mark IV tank. It was first deployed in 1918, used in action during the closing months of World War I, and in the Allied intervention in the Russian Civil War on the White Russian side, and by the Red Army, after they were captured. The tank was improved in several aspects, chiefly the new steering system and engine, but it fell short in other areas such as mechanical reliability and its insufficient ventilation. However, the Mark V was successful, especially given its limited service history, and primitive design.
Document 8: Centurion (tank): The Centurion was the primary British main battle tank of the post-Second World War period. Introduced in 1945, it is widely considered to be one of the most successful post-war tank designs, remaining in production into the 1960s, and seeing combat in the front lines into the 1980s. The chassis was also adapted for several other roles, and these have remained in service to this day.
Document 9: Mk 6 helmet: The Mk 6 helmet was the standard combat helmet of the British Armed Forces. The Mk 6 replaced the Mk IV helmet (more correctly titled - Helmet Steel MK IV, General Service). The jump in MK numbers is thought due to the confusion surrounding the MK IV helmet utilising the MK V lining, introduced in 1959. The MK 6, introduced into service from 1985, is designed to accept modern ear protection, Bowman personal radios, and respirators. The helmet is manufactured by NP Aerospace, and is reported to have an "almost unlimited service life" by the manufacturer.
Document 10: History of the tank: The history of the tank began in World War I, when armoured all-terrain fighting vehicles were first deployed as a response to the problems of trench warfare, ushering in a new era of mechanized warfare. Though initially crude and unreliable, tanks eventually became a mainstay of ground armies. By World War II, tank design had advanced significantly, and tanks were used in quantity in all land theatres of the war. The Cold War saw the rise of modern tank doctrine and the rise of the general-purpose main battle tank. The tank still provides the backbone to land combat operations in the 21st century.
Document 11: Centurion ARV Mk II: The Centurion ARV Mk II, was a British armored recovery vehicle based on the Centurion main battle tank.
Document 12: Chieftain (tank): The FV4201 Chieftain was the main battle tank of the United Kingdom during the 1960s, 1970s and 1980s. It was the "most formidable main battle tank in the world" at the time of its introduction in 1966 with the most powerful main gun and most effective armour of any tank yet made. . This was further improved while in service with Chobham armour upgrades.
Document 13: Ram tank: The Tank, Cruiser, Ram was a cruiser tank designed and built by Canada in the Second World War, based on the U.S. M3 Medium tank. Due to standardization on the American Sherman tank for frontline units, it was used exclusively for training purposes and was never used in combat as a gun tank. The chassis was used for several other combat roles however, such as a flamethrower tank, observation post, and armoured personnel carrier.
Document 14: ARL tracteur C: The "ARL tracteur C", or ARL Char C, was a French super-heavy tank developed during the late Interbellum by the "Atelier de Construction de Rueil" (ARL) company. A full-scale wooden mockup was halfly produced, but the project was terminated in favor of FCM F1, a directly competing design, which proved to be superior design. The vehicle was meant to be extremely heavy and for that time period, very heavily armored. ARL C was intended to be very long to fill up the requirement of having a long tank that could cross trenches up to 7 meters wide. The tank was multi-turretted like FCM F1; however, unlike FCM F1, ARL C had the main turret in front of the very long hull right behind the secondary turret, not in the back of vehicle. The development path of the ARL C was extremely complex, due to the existence of a number of parallel super-heavy tank projects with overlapping design goals, the specifications of which were regularly changed. For each project in turn several companies submitted one or more competing proposals.
Document 15: Armoured recovery vehicle: An armoured recovery vehicle (ARV) is an armoured vehicle used during combat for recovery or repair of battle-damaged and inoperable armoured fighting vehicles. The term "Armoured Repair and Recovery Vehicle" (ARRV) is also used.
ground_truth: 1945