The development of the Cromwell, which without being an exceptional tank was at least the first one that allowed the British to fight in conditions of almost equality with the German Panzer, dates back to the entry into service, in North Africa, of the tanks of the series Cruiser. When it was demonstrated that the characteristics of these latter no longer satisfied the necessities, mainly because these had been largely surpassed by the most recent German models, it was preferred, instead of projecting a new tank, to make modifications in an already existing series.

Probably the causes that pushed towards this decision to the competent organisms were of logistic and organizative character, but the truth is that they were cause of a notorious waste of time, because many months had to pass for the new tank of adequate characteristics to be available. Between the Crusader, tank chosen for the modifications, and the Cromwell, there were two transition models, the Cavalier and the Centaur, which, specially in the case of the Centaur, would result a failure. Only the Centaur would have chance of being used, but seemingly in a limited way, during the landings in Normandy. On the other hand, its hull would be used to ellaborate one of those strange armored elements that would accompany the waves of landing troops on the bloodstained French beaches.

The Cavalier was, in general, a Crusader with a new turret. At the same time, the Centaur remained being a Crusader, but with modifications in the gearbox mechanism and with adaptations destined to allow, as soon as it were possible, the adoption of a new engine Meteor. This engine, which in that moment was still in phase of realization, was a "terrestrial" version of the famous Rolls-Royce Merlin, propeller of the not less famous Spitfire fighters. When finally the Meteor was ready, it was immediately installed. At the same time it was replaced the 57-millimeter cannon that constituted the armament of the old Crusader. This piece started to be outdated, and besides it presented the defect of not being able to fire ammunition of American manufacture, for United States did not produce it in that caliber. So, due to logistic reasons as well, it was studied a new cannon, starting from the base of the old 57 millimeters, but in caliber 75 millimeters, as the one of the American tank Sherman.

So it was born the Cromwell, which in practice was the most important British tank. Its silhouette was not very different of what was characteristic in British tanks, but this time the tank was gifted with an adequate armament and good mobility. But over time even better characteristics were necessary, at least regarding the armament, and the cannon was replaced by a new Vickers, of 75 millimeters as well, which was installed after a restructuring of the turret. This version was denominated Comet. Returning to the Cromwell, during the war 410 exemplars were built, apart from 200 that were transformed into tank destroyers. After the war some "modified" Cromwell were transferred to other armies, such as the Austrian or the Jordanian.