By the time of World War 2 (1939-1945) the British Army adopted a two-prong assault doctrine concerning armored warfare. This doctrine involved heavier, heavily armed and armored "infantry tanks" operating alongside infantry elements while lighter and faster "cruiser tanks" were used to exploit holes created in the enemy defense by these units. As such, many types of cruiser tanks were ultimately introduced into British Army service heading into the war. One development, the "Tank, Cruiser, Mk III" (A13 Mark I)" appeared along with others during the latter half of the 1930s in preparation for war with Germany.
The Mk III followed behind the original Mk I and Mk II models, both rather primitive lightweight pre-war cruiser tanks. The Mk I was introduced in 1936 and saw 125 produced with the Mk II arriving in 1938 and seeing 175 examples completed. However, it was in the Christie suspension system that was witness by British officials of Soviet BT fast tanks and spurred interest in a similar local fast tank design. The Christie suspension system allowed for much improved off-road travel as well as optimal speed for lightweight tank types and it was envisioned that such a quality would play well into the cruiser tank approach by the British Army.
The Nuffield Mechanization & Aero Limited concern was arranged to develop and produce the new tank based on the Christie design. The design was largely rewritten (by Morris Commercial Cars) to produce a product more in line with the British Army requirement and this begat the "A13" vehicle. The original tank's crew of two was expanded to four and included a driver, commander, gunner, and loader. Armor protection ranged from 6mm to 14mm and a QF-2 pounder gun was fitted to a forward-set turret. 87 x 40mm projectiles were carried. Additional firepower was through a sole .303 Vickers machine gun and 3,750 rounds were carried for it.
The new suspension system allowed for a light aircraft engine to be fitted as the powerplant and this became a Nuffield Liberty V12 gasoline-fueled unit of 340 horsepower output. Running gear included four solid road wheels fitted to a hull side with the drive sprocket at rear and the track idler at front. The engine was installed at a compartment to the rear of the hull with the crew and turret forwards of amidships. Operational range reached 90 miles on internal fuel with a road speed of 30 miles per hour possible.
The pilot vehicle arrived in 1937 and two were eventually realized before serial production was undertaken. The British Army originally commissioned for 50 tanks but eventually took on a stock of 65 units with production spanning from 1938 to 1939. The type entered service during 1938 but was ultimately limited in production due to what eventually proved to be light armor protection and a general mechanical unreliability in the field. Pressed into combat action during the European campaigns of 1940, many were lost in action in the defense of France and their value dwindled from then on. Some managed to fight on during the Balkan and Desert campaigns but, on the whole, their design was outclassed by Axis-sponsored offerings and tactics and ultimately replaced by more competent British tank offerings of the war.
The cruiser tank design culminated with the "Cromwell" (A27M) of 1943 with the primary infantry tank counterpart being the famous "Churchill" line. Additionally, large supplies of American M4 "Sherman" Medium Tanks helped to strengthen the British armor corps inventory during the war.