Shir 2

Chieftain (FV4201)
A Chieftain Mark 11 at the Bovington Tank Museum (2013)
Type	Main battle tank
Place of origin	United Kingdom
Service history
In service	1966–present
Used by	UK, Iran, Iraq, Jordan, Kuwait, Oman
Wars	Iran–Iraq War, Gulf War
Production history
Manufacturer	Leyland Motors
Unit cost	£90,000-£100,000 (March 1967)
Specifications
Weight	55 long tons (62 short tons; 56 t)
Length	35 ft 4 in (10.77 m) – gun forward 7.5 m (24 ft 7 in) – hull
Width	12 ft 0 in (3.66 m)
Height	2.9 m (9 ft 6 in)
Crew	4
Armour	Glacis: 120 mm (4.7 in) (72°) Hull sides: 38 mm (1.5 in) (10°) Turret: 195 mm (7.7 in) (60°)
Main armament	L11A5 120 mm rifled gun
Secondary armament	2 × L7 Machine Gun
Engine	Leyland L60 (multifuel 2-stroke opposed-piston compression-ignition) 750 hp (560 kW) 6 Cyl, 19 litres.
Power/weight	11.1 hp (8.3 kW)/ton (at sprocket)
Transmission	TN 12
Suspension	Horstmann: Horizontal Coil Spring Suspension Bogies
Ground clearance	1 ft 10 in (0.56 m))
Fuel capacity	195 imp gal (890 l)
Operational range	500 km (310 miles) on roads
Speed	Road: 48 km/h (30 mph) Off road: 30 km/h (19 mph)

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.

A development of the Centurion, the Chieftain introduced the supine (reclining backwards) driver position to British design enabling a heavily sloped hull with reduced height. A new powerpack and improved transmission gave it higher speed than the Centurion despite being heavier due to major upgrades to armour protection and the armament. It remained in service until replaced by the Challenger 1 which shared a large number of the Chieftain's features.

The Chieftain was an evolutionary development of the successful cruiser line of tanks that had emerged at the end of the Second World War. Its predecessor the Centurion main battle tank is widely considered to be one of the most successful of post-war MBT designs. However, the introduction of the Soviet IS-3 heavy tank along with Soviet T-54/T-55 forced the introduction of their own Conqueror heavy tank armed with a 120 mm (4.7 in) gun. A single design combining the firepower of the Conqueror's 120 mm gun with the mobility and general usefulness of the Centurion was seen as the ideal combination.

Leyland, who had been involved in the Centurion tank had built their own prototypes of a new tank design in 1956 and these led to a War Office specification for a new tank. The General Staff specification drew on the experience of Centurion tanks in the Korean War as well as that of the Conqueror tank. The tank was expected to be able to engage the enemy at long range, from defensive positions, and be proof against medium artillery. To this end the gun was to have a greater angle of depression than the 8 degrees of Conqueror and would be equipped with better frontal armour. The tank was expected to achieve a firing rate of 10 rounds per minute in the first minute and six per minute for the following four.