The Crusader Cruiser Tank was a contemporary of the disastrous Covenator, and the immediate ancestor of the much improved Cromwell. The Mark III was the final development of the Crusader as a gun tank. It featured a 6-pdr (57mm) main gun in a longer and higher turret. The benefit of the more powerful gun was partially offset by the need for additional stowage, and therefore fewer crew. The Mark III crew was reduced from 5 in the earlier versions to only three. The Commander of the Crusader III doubled as the loader, and the gunner was also the radio operator.

Crusader III - the Anti-Aircraft variants were based on the chassis of this gun-tank

The Crusader III was initially welcomed by British armoured units in North Africa. It was fast and its 6-pdr gun helped to counter superior German armour. However, mechanical problems plagued the Crusader and it was declared obsolete by the end of the North African campaign.

The Anti-Aircraft versions of the Crusader were developed in response to the perceived need to counter German "tank-busting" ground attack aircraft. The first design using one Bofors 40mm anti-aircraft gun on a Crusader III chassis was unsophisticated in design and unsuccessful in application. The Crusader III A.A. Mk II was an improved design with an enclosed turret and twin 20mm Oerlikon cannon capable of firing explosive, incendiary or practice rounds at up to 450 rounds per minute. The main limitation was, once again, crew accommodation.

The Crusader III A.A. Mk III was the final version. It addressed the cramped crew conditions by adding a raised coaming at the rear of the turret. Crusader AA II and III vehicles were used in front line duties with British and Polish armoured units after D-Day. However, due to the effective air cover by the RAF they only saw limited action.