The original aforementioned 12.7mm heavy machine gun utilized for ranging was eventually replaced by the aptly-named "Tank Laser Sight" (TLS) system which took over the same role albeit in a more technological fashion.
Leyland developed the L60 multi-fuel compression ignition engine of 750 horsepower output at 2,100rpm and it was this system that powered the definitive Chieftain mark. This supplied the vehicle with a top speed of 30 miles per hour on ideal road surfaces and less so on uneven, off road-minded terrains. Operational range was 250 to 280 miles depending on terrain and driving habits. A fire extinguishing system was installed at the engine compartment for obvious reasons. In profile, the powerplant forced a raised engine compartment but in no way impeded performance nor the relatively low overall profile of the tank itself - turret included. The vehicle could ford up to 1.066 meter high water sources (aided by an integrated "splash board" identified around and ahead of the driver's area) and cross 3.149 deep trenches. Gradients of 60% could be managed as well. The hull was suspended atop a Horstmann suspension system developed by Hortsmann Defence Systems Ltd. If the Chieftain had one limitation it was in her selection of a multi-fueled engine design which was said to have never reached the intended output level as expected.
The initial Chieftain production mark was the Mk 1 which served in 40 delivered examples utilized primarily for trials and tanker training beginning in 1965. The Mk 2 became the initial service-ready model and these were supplied with 650 horsepower Leyland engines. A new commander's cupola was devised, an uprated engine introduced and additional equipment added to make the Mk 3 variant. The final definitive Chieftain production model became the Mk 5 and these added NBC protection units at the turret bustle as well as further uprated engines.
The Mk 6, Mk 7, Mk 8 and Mk 9 marks were essentially upgrades of earlier production models that introduced improved engines. The following Mk 10 was based on the Mk 9 upgrade and included the "Stillbrew Crew Protection Package" (SCPP) along the turret as well as an improved fire control system. The Mk 11 was itself an upgrade of the Mk 10 which saw the original IR/white light searchlight replaced with the Barr & Stroud "Thermal Observation and Gunnery System" (TOGS). TOGS allowed for adverse weather and night fighting capabilities which expectedly broadened the tactical scope of Chieftains for the better. The Mk 12 and Mk 13 variants were proposed Chieftain upgrades that would have featured additional improvements throughout but these marks were done in by the arrival of the excellent Challenger 2 series main battle tank. The "Chieftain 900" was a developmental Chieftain derivative protected by "Chobham" armor, a special breed of composite armor born out of British research at Chobham Common in Surrey.
900 Chieftain tanks were ultimately manufactured for the British Army. Its acceptance and use by one of the major military powers of the day inevitably drew interest from allies seeking a more modern MBT solution. As such, the Chieftain line also proved an export success beginning with Kuwait's purchase of 175 total units (these being Chieftain "Mk 5TK" models). Operators went on to include both Iran and Iraq (captured Iranian examples), Jordan (as the "Shir 1" / "Khalid" series) and Oman. Iran was by far the largest foreign operator of the Chieftain, receiving 707 examples in their MBT, AVLB and ARV form before the Islamic Revolution of 1979. Jordan took delivery of 274 units. Oman managed 27 (12 refurbished ex-British Army and 15 new-build as the "Qayd al Ardh"), these received in the early-to-mid 1980s.
During the Iran-Iraq War of the 1980s, Iraq captured around 100 Chieftains and operated at least 30 of these for time before passing them on to Jordan. The Iranians went on to upgrade their Chieftains to the newer "Mobarez" standard.
Like other combat tank systems before it, the Chieftain chassis and hull were adaptable for a broader range of battlefield applications to include a bulldozer variant, a mine clearing vehicle, an armored recovery vehicle (FV4204 ARV), a bridgelayer (FV4205 AVLB), armored recovery repair vehicle (FV4204 ARRV) and armored engineering vehicle (Armored Vehicle Royal Engineers - AVRE). As also the case with previous MBT entries, the Chieftain's derivatives outlasted the original combat hulls by decades. The Chieftain chassis was also the basis of the Chieftain "Marksman" self-propelled air defense vehicle mounting the "Marksman" series turret with 2 x 35mm cannons. The Chieftain "Sabre" was similar in scope, fitting a turret with 2 x 30mm cannons and intended for mobile air defense.
By 1996, the Chieftain Main Battle Tank was moved out of frontline service within the British Army inventory, replaced by the Challenger 1 and Challenger 2 series tanks. However, the many battlefield guises it produced remained in service for some time later, proving their worth and then some in operations to follow. The Challenger 1 came online in 1983 before being itself replaced by the more capable Challenger 2 in 1998.
Content ©MilitaryFactory.com; No Reproduction Permitted.