The type would serve as an interim MBT for the Iranian government commissioned the British to design and develop an all-new MBT to take on the name of 'Shir 2'. Through an agreement with the British, work then began on an 'improved' Chieftain for the Iranian Army to be known by the name of 'Shir 1' and 125 of these were under order. Iran became the largest foreign operator of the Chieftain and received over 700 examples. Regardless, the Chieftain proved the most powerful tank of her time - a tremendous blend of armor and firepower at the cost of speed - that is until seated by the equally excellent German Leopard 2.

If the Chieftain held any limitations it was in her engine which was never able to fully realize her output. The Chieftain became another excellent British tank design and this form mounted a reliable multi-fueled engine as well as a powerful and highly accurate 120mm main gun. By the time of the 1960s, there was a technological change in the wind and this produced the impressive Chieftain MBT for the British Army. The Centurion went on to become a post-war success story which saw thousands built and included various derivatives. The MBT could now accomplish all of what was required in preceding designs. However, it was the Centurion that truly laid the foundation for the 'main battle tank' category, ultimately being responsible for doing away with specifically-built tanks in the light, medium and heavy weight range classes. It was not until World War 2 that armored warfare truly came into its own, beginning an 'arms race' of sorts concerning tanks between world powers that ultimately produced the excellent Soviet T-34 Medium Tank and German Panther series as well as the notable American M4 Sherman and, ultimately, the late-war American M26 Pershing and British Centurion tanks. Within time, the 'lozenge-shaped' vehicles of the First World War evolved to include cannon armament fitted to traversing turrets (the French FT-17 being a prime example) and less crew to manage the various required functions of the vehicle. However, these were hardly representative of the vehicles that we know today to be 'Main Battle Tanks'. The original combat 'tank' was born out of the fighting that was World War 1.

Challenger mk 2 main battle tank