WWII Tech Pubs Briefing

Written by
Daren Beazley

Cruiser tank “Agility”, commanded by Sgt. Ron Huggins of the 10^th Royal Hussars, 2nd Armoured Brigade, faces the enemy at Huppy, France, May 27, 1940. 

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Overview

The A13 was an immensely important step forward in British tank evolution, for it was the first British cruiser tank to incorporate a suspension system that stemmed from the designs developed by the American designer J Walter Christie. His coil-spring suspension system was to be included in the design of all future British cruiser tanks thereafter. However, it should be noted, that the most famous tank to incorporate this suspension system was the Soviet manufactured T-34, arguably the best all-round tank of the war.

The man responsible for the introduction of the Christie suspension into British vehicles was a Lt. Col. Martel, who was appointed Assistant Director of Mechanisation to the War Office in the late summer of 1936. Shortly after his arrival, Martel attended the Soviet Army autumn training manoeuvres in September as an observer where he was to see the Soviet BT tank in action for the first time and he was suitably impressed. The BT tank incorporated a Chritie suspension and demonstrated good performance and speed. It was based upon the British ’16 tonner’ of 1929 and was available in large numbers. Upon his return to the War Office, Martel set out to instigate the design of a vehicle with vastly superior performance than had previously been seen in Britain. This was to be achieved primarily by adopting the Christie suspension along with a powerful lightweight engine.

Two Christie demonstration vehicles were ordered from the United States and upon their arrival it was found that the suspension incorporated compression springs along with large-diameter rubber rimmed road wheels. Thus the vehicle was therefore capable of running at high speed either with or without tracks. It was quickly decided to dispense with the ‘trackless’ running capability as it was seen as an unnecessary complication. A decision was then taken to widen the vehicle so that a 2pdr cannon along with associated turret could be fitted. Funds were made available at the end of 1936 to build two prototypes and Morris Commercial Cars Ltd were asked to undertake the initial design. The prototypes were designated A13E2 and A13E3 with the original Christie demonstrator vehicle given the designation A13E1.

Nuffield Mechanisations and Aero Ltd were, at the time, licensed to manufacture a high performance American designed World War I aero engine called the Liberty, which when mated to the A13E2 prototype chassis in October 1937 produced a vehicle capable of attaining a top speed of 35mph (56 km/h). Certain mechanical problems, due mainly to the high speed of the vehicle, were soon highlighted and overcome. The speed of the vehicle was ‘governed’ to 30mph. The clutch and transmission were altered and shorter pitched tracks were provided. By early 1938 a production order for 65 vehicles was confirmed with Nuffield, a subsidiary of Morris Commercial Cars Ltd. Deliveries to the army began in early 1939 and by September of the same year all 65 had been delivered. These vehicles were officially known as Cruiser Tank, Mark III (A13 Mk I).

In early 1939 a decision was taken to increase the armour thickness of all British cruiser tanks to a standard 30mm and so one Mark III pilot model was modified to these specifications. Extra armour plate was placed upon the nose, glacis and turret. Two additional armor plates reinforced each turret wall, configured so that one plate sloped out and down from the turret’s top edge while second attached to the bottom edge sloped out and up. The two plates met and with the original turret wall enclosed a triangular hollow that gave the turret a distinctive angled look. German designers would later use this ‘spaced armour’ effect to defeat hollow charged projectiles fired from infantry held anti-tank weapons such as ‘Piat’ and ‘Bazooka’.

Amazingly, testing showed that the weight of the extra armor did not appreciably degrade the tank’s performance, and all Mark IIIs were so modified. These vehicles, officially designated Cruiser Tank, Mark IV (A13 Mk II), were used almost exclusively by the 1st Armoured Division in France the following year.

Thereafter, Nuffield undertook main production of Cruiser Mark IV’s. The designation Cruiser Tank, Mark IVA (A13 Mk II) was given to later production vehicles, the difference being that the Vickers co-axial machine gun was replaced by one manufactured by Besa. These vehicles were also used in France by 1st Armoured Division where they took part in the Allied counterattacks against the Somme River bridgeheads, May 23-24, 1940. Thereafter, they fought to defend Calais and Dunkirk. Cruiser A13’s were also issued to 7th Armoured Division during the North Africa campaign. Total production of the Cruiser Tank Mk IV series amounted to some 655 examples but production ceased in 1941 as it became apparent that the vehicle was totally outclassed by the heavier and more powerful German tanks.

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Variants

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Specifications

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