The Chieftain FV4201 was the main battle tank of the United Kingdom during the 1960s, 1970s and 1980s. It was one of the most advanced tanks of its era, and at the time of its introduction in 1966 had the most powerful main gun and most effective armour of any tank in the world. The Chieftain also introduced a supine (reclining backwards) driver position, enabling a heavily sloped hull with reduced height. It remained in service until replaced with the Challenger 1. The Chieftain was an evolutionary development of the successful cruiser line of tanks that had emerged at the end of the Second World War. British engineers had learned during the war that their tanks often lacked sufficient protection and firepower compared to those fielded by the enemy, and that this had led to high casualty levels when faced with the superior German tanks in World War II. Centurion addressed this to a great degree, combining higher levels of armour and an improved gun, which made it at least equal to any...