Cruiser Mk III

Tank, Cruiser, Mk III (A13 Mk I)
Type	Cruiser tank
Place of origin	United Kingdom
Service history
In service	1938–1941
Used by	British Army
Wars	Second World War
Production history
Designer	Morris Commercial Cars
Designed	1936–1937
Manufacturer	Nuffield Mechanisations & Aero, Limited
Produced	1938–1939
No. built	65
Specifications
Weight	14 Long tons (14.2 tonnes)
Length	19 ft 8 in (6.0 m)
Width	8 ft 4 in (2.54 m)
Height	8 ft 6 in (2.59 m)
Crew	4 (commander, gunner, loader, driver)
Armour	6–14 mm
Main armament	QF 2-pounder gun 87 rounds
Secondary armament	.303 Vickers machine gun 3,750 rounds
Engine	Nuffield Liberty V12 petrol 340 hp (250 kW)
Suspension	Christie
Operational range	90 mi (140 km)
Speed	30 mph (48 km/h)

The Tank, Cruiser, Mk III, also known by its General Staff specification number A13 Mark I, was a British cruiser tank of the Second World War. It was the first British cruiser tank to use the Christie suspension system, which gave higher speeds and better cross-country performance; previous cruiser tank models had used triple wheeled bogie suspension.

British cruiser tank design began with the Mk I and somewhat heavier Mk II in the mid-1930s. Just as prototypes were arriving in 1936, General Giffard LeQuesne Martel, a pioneer in tank design who had published works on armoured warfare and pioneered the lightly armoured "tankette" to enhance infantry mobility, became Assistant Director of Mechanization at the War Office.

Later that year, Martel witnessed demonstrations of Soviet tank designs, including the BT tank, which had been influenced by American J. Walter Christie's work. Martel urged the adoption of the Christie suspension and Christie's practice of using a lightweight aircraft engine, such as the Liberty Engine. The government authorized the purchase and licensing of a Christie design via the Nuffield Organization, rather than contact the Soviet authorities.

The vehicle obtained from Christie became the basis of the Cruiser Mk III (A13). It had to be extensively redesigned by Morris Commercial Cars as it was too small and had several faults that Christie had not addressed. A new company Nuffield Mechanization & Aero Limited was formed for the development and production of the design.

At a meeting of the General Staff, an official specification was determined, which included 30 mm (1.2 in) armour, a 2-pounder gun and a road speed of 30 miles per hour (48 km/h). A subsequent review of the specification by Martel and Percy Hobart approved 30 mm armour all round provided cross-country speed could be kept at 25 miles per hour (40 km/h). Pending the delivery of the A13, an interim design was approved from the A7, A9 and A10, the A9 being selected. Orders for the resulting Mk. I's were limited pending the arrival of the A13.