The Chieftain Main Battle Tank (MBT) 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 of the contemporary medium tanks. However, the introduction of the Soviet IS-3 heavy tank forced the introduction of their own Conqueror heavy tank, armed with a 120 mm gun. A single design combining the firepower of the Conqueror’s 120 mm gun with the mobility and general usefulness of the Centurion would be ideal.
Leyland, who had been involved in Centurion, 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 experience of Centurion in the Korean War and Conqueror. The tank was expected to be able to engage the enemy at long range and from defensive positions, 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 better frontal armour. The tank was expected to achieve 10 rounds per minute in the first minute and six per minute for the following four.
The first few prototypes were provided for troop trials from 1959, this identified a number of changes. Changes to address engine vibration and cooling resulted in redesign of the rear hull.
This increased the design weight to nearly 50 tons and as such the suspension (which had been designed for 45 tons) was strengthened. Track pads had to be fitted to protect roads from damage and the ground clearance increased. The design was accepted in the early 1960s.
Britain and Israel had collaborated on the development in its latter stages with a view to Israel purchasing and domestically producing the vehicle. Two prototypes were delivered as part of a four year trial. It was eventually decided not to sell the marque to the Israelis however which prompted Israel to follow its own development programme.
In 1957 NATO had specified that its forces should use multi-fuel engines. The early BL Engine delivered around 450 bhp to the sprocket which meant a top road speed of around 25 mph and cross country performance was limited.
This was further hampered by the Horstmann coil spring suspension, which made it a challenge to drive cross country and provide the crew with a comfortable ride. Due to the cylinder linings being pressure fitted, coolant leaks within the cylinder block were common, resulting in white smoke billowing from the exhaust.
In the late 1970s engine design changed with the introduction of Belzona which was used to improve the lining seals. Engine output also increased with later engines delivering some 850 bhp to the sprocket. This meant better performance and an increased speed. Cross-country performance remained limited however.
Chieftain design included a heavily sloped hull and turret which greatly increased the effective thickness of the frontal armour – 388 mm on the glacis (from an actual thickness of 120 mm and 390 mm on the turret). It had a mantletless turret, in order to take full advantage of reclining the vehicle up to ten degrees in a hull-down position.
For security reasons, early prototypes had a canvas screen covering the mantlet and a sheet metal box mounted over the sloping glacis plate to disguise the configuration of the vehicle.
The driver lay semi-recumbent in the hull when his hatch was closed down, which helped to reduce the profile of the forward glacis plate. The commander, gunner and loader were situated in the turret. To the left side of the turret was a large searchlight with infra-red capability in an armoured housing.
The Leyland L60 engine is a two-stroke opposed piston design intended for multi-fuel use so that it could run on whatever fuel was available. In practice the engine did not deliver the expected power, and was unreliable, estimated to have a 90% breakdown rate, but improvements were introduced to address this. Primary problems included, cylinder liner failure, fan drive problems and perpetual leaks due to vibration and badly routed pipework. However, as the engine power improved the tank itself became heavier.
The tank was steered by conventional tillers hydraulically actuating onto external brake discs. The discs worked via the epicyclic gearbox providing “regenerative” steering. The gearbox was operated motorcycle-style with a kick up/kick down “peg” on the left which actuated electro-hydraulic units in the gearbox; the accelerator was cable operated by the right foot.
In the turret the loader was on the left and the gunner on the right of the gun with the commander behind the gunner. The suspension was of the Horstmann bogie type, with large side plates to protect the tracks and provide stand-off protection from hollow charge attack.
The main armament was the 120 mm L11A5 rifled gun. This differed from most contemporary main tank armament as it used projectiles and charges which were loaded separately (known as Breach Loading), as opposed to a single fixed round (known as Quick Firing).
The charges were encased in combustible bags. Other tank guns, such as on the Conqueror, needed to store the spent shell cartridges or eject them outside. The combustible charges were stored in 36 recesses surrounded by a pressurised water/glycol mixture – so-called “wet-stowage”. In the event of a hit which penetrated the fighting compartment, the jacket would rupture, soaking the charges and preventing a catastrophic propellant explosion.
As there was no shell case, the firing of the charge was by vent tubes automatically loaded from a magazine on the breech. Due to the length of the gun which required balancing and the need for storage space, the turret has a large overhang to the rear. This contains radios, ammunition, fire control equipment and has further stowage externally.
The gun could fire a wide range of ammunition, but the most commonly loaded types were high explosive squash head (HESH), armour-piercing discarding sabot (APDS), or practice round equivalents for both types. Chieftain could store up to 64 projectiles (though a maximum of 36 APDS, limited by the propellant stowage).
The gun was fully stabilised with a fully computerised integrated control system. The secondary armament consisted of a coaxial L8A1 7.62 mm machine gun, and another 7.62 mm machine gun mounted on the commander’s cupola. The Chieftain Tank also had an NBC protection system, which Centurion lacked.
The initial Fire-control system (FCS) was the Marconi FV/GCE Mk 4. A .50-inch ranging gun was mounted above the main gun (with 300 rounds available). This fired ranging shots out to a maximum of 2,600 yards at which point the tracer in the ranging rounds burned out. The tank commander had a rotating cupola with nine vision blocks – giving all round view – and a periscope, plus the 7.62 mm machine-gun and an infrared (IR) projector coaxial with the weapon.
The aiming systems were provided for both gunner and tank commander; they had 1x or 8x selectable magnification power, and they were replaceable with IR vision systems for the night operations (3x magnification power). The commander could rotate his cupola to bring his sight onto a target and then engage the mechanism that brought the turret (known as contra-rotation) round on to the correct bearing so that the gunner could complete the aiming.
The left side of the turret had a large searchlight with an infra-red filter inside an armoured box, with a relatively long range – 1 to 1.5 kilometres.
From the beginning of the 1970s, the Mk 3/3 version replaced the ranging gun with a Barr and Stroud LF-2 laser rangefinder with a 10 km range. This allowed engagements at much longer ranges, and also could be linked to the fire control system, allowing more rapid engagements and changes of target.
On later models fire control was provided by the Marconi IFCS (Improved Fire Control System), using a digital ballistic computer, the 14th/20th King’s Hussars was the very first regiment to test and later be equipped with this new system. The upgrade was not finished until the end of 1980, when some examples (but not the majority) had the IR searchlight replaced with TOGS. Many later examples had Stillbrew armour, intended to defeat Soviet 125 mm tank guns and heavy anti-tank missiles. These became the Mark 13 version.
On another ‘first to have’ point, the 14th/20th King’s Hussars were also chosen to trial and test the new communications system known as BATCO which was later implemented with the entire British Army.
Like its European competitors, Chieftain found a large export market in the Middle East, but unlike Centurion, it was not adopted by any other NATO or Commonwealth countries.
Chieftain proved itself capable in combat and able to be upgraded with enhancements both for overall improvement and to meet local requirements. The marque was continuously upgraded until the early 1990s when it was replaced by Challenger 1.
The final Chieftain version used by the British Army until 1995, incorporated “Stillbrew” armour named after Colonel Still and John Brewer from the Military Vehicles and Engineering Establishment (MVEE), the Improved Fire Control System (IFCS) and the Thermal Observation Gunnery Sight (TOGS). The last British Regiment equipped with Chieftain was 1st Royal Tank Regiment, who were based at Aliwal Barracks, Tidworth.
The first model was introduced in 1967. Chieftain was supplied to at least six countries, including Iran, Kuwait, Oman and Jordan. An agreement for sales to Israel and local production was cancelled by the British Government in 1969, despite considerable Israeli technical and tactical input into the development of the tank, especially the capacity to operate successfully in desert environments, and the provision for the tank to make good use of hull-down deployment.
Two examples were delivered to and extensively trialled by the Israeli Armoured Corps. This experience spurred the creation of the indigenous Israeli Merkava, the development programme of which was led by General Israel Tal, who had worked closely with the British in the Anglo-Israeli Chieftain project. The largest foreign sale was to Iran, which at the recommendation of General Tal, took delivery of 707 Mk-3P and Mk-5P, 125–189 FV-4030-1, 41 ARV and 14 AVLB before the 1979 revolution. Further planned deliveries of the more capable 4030 series were cancelled at that point.
It was in the Middle East that the Chieftain was to see all of its operational experience. First, it was used extensively by Iran during the Iran–Iraq War of 1980–88, including the largest tank battle of the war, with mixed results as many suffered from chronic engine problems. The Chieftain remains in service in Iran with Mobarez Tank being its upgraded version.
Kuwaiti Chieftains participated in the 1990 Iraq–Kuwait War. The Kuwaiti 35th Armoured Brigade fought at the Battle of the Bridges against elements of the Iraqi Hammurabi and Medina divisions before withdrawing over the Saudi border 136 Kuwaiti Chieftains were lost. Only 7 tanks managed to survive the war with Iraq.
The 14th/20th Kings Hussars
HRH Princess Anne meets the Regiment in Paderborn in 1969 as she became the Colonel-in-Chief and is taught to drive Chieftain for the first time by S/Sgt F. J. Baker (1420H)