The aftermath of the First World War produced a variety of ideas and opinions about the future of tanks. At one extreme were views that tanks would be of no further use. At the other extreme there were claims that in the future existing armies would be replaced by fleets of tanks.
An example of the former attitude is the often quoted remark made by Major General L. Jackson, Master General of the Ordnance, in December 1919 at the Royal United Service Institution that ‘The tank proper was a freak. The circumstances which called it into existence were exceptional and are not likely to recur’.1 To some, evidently, the usefulness of tanks was confined to trench warfare and the latter was not expected to occur again.
The other extreme is exemplified by a paper entitled ‘A tank army’ written during the war by Captain G. le Q. Martel, who assisted Colonel Fuller at the headquarters of the Tank Corps. It described a future army composed almost entirely of different types of tanks corresponding to the principal types of contemporary warships.2 Fuller himself adopted similar ideas and immediately after the war began to write of ‘tank fleets’ and of battles that in future would ‘more and more approximate to naval actions’.3
The appeal of the naval model is understandable in view of the fact that warships represented an earlier form of mobile weapon platforms, which is what Fuller rightly recognized tanks to be.4 However, the environments in which warships and tanks operated were obviously very different. Armies could not, therefore, be expected to operate on land as warships did at sea. Nevertheless, as late as 1931 Fuller was still forecasting that tanks ‘will operate on somewhat similar lines to a fleet at sea’.5
The policy that armies generally adopted was to accept tanks but only as an auxiliary of the infantry and operating at the pace of the latter. A possible advance on the prevailing stance was indicated by a study produced in 1919 by General Estienne at the request of the French commander-in-chief. In it Estienne foresaw the existing Renault FT light tanks being replaced by more powerful chars de combat that would play a leading role in future battles.6 Two years later Estienne enlarged on his views in a lecture delivered in Brussels in which he spoke of the potential strategic and tactical advantages of a future mechanized army of 100,000 men that would include 4,000 tanks and armoured infantry and was capable of moving 80km in one night.7 However, his views were ignored. In particular, while he and a few other French Army officers advocated the creation of an independent tank arm, the headquarters of the artillerie d’assaut that provided tank units with a degree of autonomy were abolished in 1920. Instead, tank units were put under a subdivision of the Infantry Department, which stultified further tactical and technical development.
A similar situation arose in the United States, where the wartime Tank Corps was abolished under the National Defense Act of 1920 and tanks were assigned to the infantry, becoming its auxiliaries. In keeping with this the General Staff declared in 1922 that ‘the primary mission of the tank is to facilitate the uninterrupted advance of the rifleman in the attack’.
Apart from France and the United States only Britain had the means at the time to develop the use of tanks further. In consequence it was left to the British Army to take the lead in the development of a more mobile and effective use of tanks.
The lead that the British Army took was due to a large extent to the conjunction of two events. One was the establishment of the Royal Tank Corps, which in 1923 succeeded the wartime Tank Corps and became a separate arm, due to a considerable extent to the efforts of Fuller. Its strength amounted to only four tank battalions and some armoured car companies, but its status provided a degree of freedom to explore new methods of operation free of the constraints of infantry tactics.
The other event underlying the British Army’s lead was its acquisition of tanks that were in advance in several respects of other contemporary tanks and that lent themselves to the development of new tactics. One of their features was a considerably higher speed than that of the earlier tanks, which was a consequence of them being designed as an alternative to Johnson’s Light Infantry Tank referred to in the previous chapter and ordered in 1920 at the instigation of Fuller.8 This prompted the War Office department responsible for the procurement of equipment to order another light tank from the Vickers company. Experimental versions of both tanks were built and tested by the end of 1921, with Johnson’s proving capable of more than 20mph while Vickers’ was slower than the wartime Medium C (which had a maximum speed of 7.9mph), as Fuller gleefully observed in his memoirs.9
However, in other respects Vickers’ tank was better, in spite of the praise bestowed on Johnson’s model. In particular, its general configuration was superior, being more like that generally adopted for tanks later, and it was the first British tank to have a rotating turret, while Johnson’s still had a fixed superstructure with a fighting compartment similar to that of the Medium D, which was considered unsatisfactory by General Elles, the wartime commander of the Tank Corps. Moreover, Johnson’s tank was only armed with machine guns while Vickers’ also had a 47mm gun. Otherwise both tanks represented an advance on the wartime British tanks in having sprung suspensions instead of rigidly mounted track rollers, but that of the Vickers tank was more robust.
Low speed, the one major shortcoming of the Vickers tank, was due to its use of an unconventional hydrostatic transmission. This type of transmission was used successfully on warships, but Vickers’ designers did not appear to appreciate how inefficient it would be when used to drive vehicles, with the result that much of the engine power was dissipated as heat and far less of it was consequently available to drive a vehicle.
As a result of its poor automotive performance Vickers’ original tank was abandoned in 1922, as was Johnson’s development work. However, in the same year Vickers came up with a second tank and this was adopted by the War Office as Vickers Light Tank Mark I, although it became far better known by its later name of Vickers Medium.
The first Vickers Medium was delivered in 1923. It weighed 11.75 tonnes and looked as if it had been hastily put together by mounting the turret of a Rolls-Royce armoured car on the chassis of a high speed artillery tractor. However, it retained the best features of Vickers’ original design, which included a 47mm gun mounted in a rotating turret that was large enough to accommodate not only a gunner but also a tank commander free to exercise tactical control and ensure a more effective use of the tank. At the same time Vickers Medium was almost as fast as Johnson’s tank, its nominal maximum speed being 18mph but in practice it was capable of more than 20mph.
Eventually 166 Vickers Medium Tanks Marks I and II were built for the British Army, which was just enough to equip the tank battalions of the Royal Tank Corps, and they were the only new tanks to appear in quantity anywhere in the world between the end of the First World War and 1929. During this period they were also by far the fastest tanks in service, their maximum speed being almost four times that of the typical contemporary tank, which was still the Renault FT. The Royal Tank Corps was therefore uniquely well equipped to develop new, more mobile methods of employing tanks and to some extent these were driven indirectly by its tanks.
At first new ideas about the employment of tanks came primarily from Fuller, who wrote extensively on the subject. The writings started in 1919 with an essay which won a Royal United Service Institution competition and in which Fuller proposed a ‘New Model Army’ built around the capabilities of tanks. The divisions of this army were to incorporate 12 infantry battalions each with an integral tank company as well as a divisional tank battalion and two regiments of horse cavalry. This amounted to a surprisingly gradualist proposal for the future use of tanks, although ultimately Fuller expected tanks to replace infantry and cavalry.10
The publication of Fuller’s essay led to a meeting with Captain B. H. Liddell Hart and a long association between the two.11 In 1922 Liddell Hart followed Fuller by also writing about a ‘New Model Army’ but proposed a more practical organization for its divisions, which were to have separate tank and infantry battalions – the latter in armoured carriers – and no horse cavalry. But he did not differ greatly from Fuller in expecting further mechanization to lead to ground forces being ‘composed primarily of tanks’. However, he did not propose to dispense entirely with the infantry, a small contingent of which would be retained as ‘land marines’.12
Like Fuller, Liddell Hart wrote extensively on the use of tanks and related matters, and both assisted the development of new methods of employing tanks through personal contacts and by publicity, particularly in the case of Liddell Hart who in 1925 became the military correspondent of The Daily Telegraph. Their writings made Fuller and Liddell Hart well known internationally, and on the strength of their writings they came to be regarded as the apostles of mechanized warfare.
However, the actual development of new and more effective methods of using tanks was carried out by others. It began with a memorandum written in 1924 by Colonel (later Brigadier) G. M. Lindsay, the inspector of the Royal Tank Corps, in which he proposed the establishment of an ‘Experimental Mechanical Force’. As nothing happened, Lindsay repeated his proposal in another memorandum, which he submitted to the chief of the Imperial General Staff, General Milne, through Fuller, who was Milne’s military assistant. Milne agreed with Lindsay’s ideas and consequently an Experimental Mechanized Force was assembled in 1927 on Salisbury Plain.13 Fuller was offered the command of it but rejected the offer because of dissatisfaction with some of the administrative arrangements, losing thereby the opportunity of putting some of his ideas into practice.14
In spite of this, the composition of the Experimental Mechanized Force reflected the ideas of Fuller as well as those of Lindsay, who wanted it to be predominently a force of tanks and other armoured vehicles. Its principal components were therefore a battalion of Vickers Medium tanks and a mixed battalion of armoured cars and tankettes, which were supported by four batteries of motorized and one of self-propelled artillery and a motorized engineer company. There was no infantry in it except for a motorized machine gun battalion that could only play a relatively passive role of holding ground.
To some extent the Experimental Mechanized Force was a scratch collection of the available units and its vehicles were of several different types, which made it difficult to co-ordinate the action of its components.15 Nevertheless, it was the first mechanized formation ever to be assembled and its organization and operational trials aroused considerable interest in Europe and the United States.
Experiments in which the Experimental Mechanized Force took part in 1927 were followed by others during the 1928 training season, by which time it was renamed the Armoured Force, but it was then dissolved. A conclusion drawn from the experiments that had been carried out was that the unarmoured components of the force were a drag on the armoured ones, which reinforced the idea that mechanized formations should consist almost entirely of tanks.
This idea was embodied in the first armoured force manual entitled Mechanised and Armoured Formations and popularly known as the ‘Purple Primer’, which was issued by the War Office in 1929.16 The manual was drafted by a Royal Tank Corps officer, Lieutenant Colonel C. Broad, and envisaged a future army that would include light and medium tank brigades consisting very largely of tanks as the principal mechanized formations. Their proposed composition severely limited the ability of the brigades to carry out independent operations but, nevertheless, an ‘all-tank’ brigade became the basis of further experiments.
A tank brigade was actually formed on a provisional basis when experiments were resumed during the 1931 training season. It consisted of three mixed battalions of light and medium tanks and one of Carden Loyd machine gun carriers, which were used in lieu of light tanks of which there was a shortage. The relatively homogeneous composition of the brigade made it easier to develop new methods of controlling and manoeuvring tank units, which involved among other things pioneering the use of radios, which began to be available in 1929. By the end of the 1931 training season the brigade demonstrated that it could manoeuvre as a whole and not merely operate as so many individual tanks.17
The Tank Brigade was assembled again in 1932, and after a break was reassembled and put on a permanent footing in 1934. For the following four years it constituted the only mechanized formation of the British Army and contained most of its tanks. In the course of its existence it made important advances in the technique of mobile mechanized operations, but it was clearly not a self-contained formation of several complementary arms capable of a variety of offensive and defensive operations, instead being only capable of strategic manoeuvres that seem to have been expected to yield success without too much fighting.
The emphasis on operational mobility rather than tactical effectiveness based on fighting ability, which characterized the atmosphere in which the Tank Brigade was created and developed, also applied to the design of British tanks during the 1920s and 1930s.
The first tank to come after the Vickers Medium was the outcome of an apparent if only temporary revival of interest in trench warfare by the War Office, which in 1922 asked Vickers to produce the design of a heavy tank that would replace the wartime Mark V.18 It was to be turretless but have a hull-mounted 47mm gun and small sponsons with machine guns, which made its configuration resemble that of the wartime Mark VI designed in 1917 but never built, and showed that the War Office was still thinking in terms of the original types of tanks. In contrast Vickers offered as an alternative a very original design. This was accepted, the resulting tank being given the A.1 designation and later called Independent. Its principal feature was that it had as many as five turrets: a main turret mounting a 47mm gun and a machine gun and manned by a crew of three, and around it four small, one-man machine gun turrets. A.1 was not the first tank to have more than one turret, as the French 2C heavy tank already had a second turret at the rear of its hull and US Model 1921 and Model 1922 experimental medium tanks had a small machine gun turret on top of their main turret. However, A.1 was the first tank to have more than two turrets. As such it aroused considerable interest but only one other tank, the Soviet T-35, followed its example in having five turrets, although several other tanks built later had three turrets.
Auxiliary turrets apart, the general configuration of the A.1, which incorporated a driver’s station in the front of the hull and an engine compartment at the rear, represented a considerable advance on that of the Vickers Mediums. But, in spite of its weight of 32 tonnes, its main armament was not more powerful than theirs and its armour was only slightly thicker than that of the Renault FT light tank. However, it was relatively mobile, having a maximum speed of 20mph.
Only one A.1 was actually built, but it attracted attention around the world when it appeared in 1926 at a large scale demonstration of armoured vehicles staged for the benefit of the British government and Commonwealth prime ministers. The ‘Independent’ name later given to it led to suggestions that it was intended for strategic strikes carried out independently by mechanized forces, but there is no evidence of this.19
The construction of the A.1 was followed by the development of a new medium tank, which was designated A.6 but came to be known generally as the ‘Sixteen Tonner’. The A.6 was designed at Vickers to an outline specification produced by a committee of the Royal Tank Corps of which Fuller was a member, but followed the general configuration of the A.1, or Independent, and like the latter was actually designed by C. O. Woodward working under the general direction of Sir George Buckham. However, it had only two auxiliary machine gun turrets instead of four. Its main turret again mounted a 47mm gun and was large enough not only to accommodate the optimum size crew, consisting of a commander, gunner and loader, but also an observer, whose inclusion was an indulgence in view of the extra space and weight that this involved.
The first two of three prototypes of the A.6 were ready in 1928 and it was generally highly regarded. In fact, a 1930 War Office document described the A.6 as ‘probably the best medium tank in the world’.20 In spite of this the A.6 was not adopted by the British Army. Instead, a decision was taken in 1928 to base on it a new Mark III medium tank. This turned out to be very similar to the A.6 except for the main turret, which had a crew of three instead of four and a bustle to house the radio that had come into use.
Two Medium Mark III tanks were built by the Royal Ordnance Factory at Woolwich in 1929 and one by Vickers in 1931.21 Trials of them were successfully completed by 1933 but General A. Brough, who became Director of Mechanization in 1932, decided to abandon the development of the Mark III because it was considered too expensive to produce in any quantity, particularly in the prevailing economic circumstances. Instead, he decided to develop a simpler and less expensive medium tank. His decision has been severely criticized later, to the extent of being called ‘a fatal mistake’.22 In fact, a similar decision to build a simpler and less expensive medium tank than the Mark III had already been taken in 1928 by Brough’s predecessor. It resulted in the A.7 tank, two of which were built by the Royal Ordnance Factory by the end of 1929.
The A.7 very sensibly dispensed with the auxiliary machine gun turrets, which were replaced by a single machine gun simply mounted in the front of the hull and operated by a gunner sitting alongside the driver, while the main turret was manned by a crew of three. This meant that the configuration of the A.7 was basically the same as that adopted later during the Second World War for most tanks and in advance of that of the Mark III Medium. In other respects, such as armour and main armament, the A.7 did not differ from the Sixteen Tonner and the Mark III. It could therefore have been developed into a medium tank that was as effective as the Mark III but was simpler, lighter and should have cost less to produce. However, it was not adopted, although a number of its features were incorporated later in other tanks.
When the decision was taken to abandon the Mark III, the development of a simpler and less expensive medium tank was started afresh in 1934 at what had become Vickers Armstrongs after Carden Loyd Tractors’ takeover in 1928. It was carried out under the direction of Sir John Carden, who came to be highly regarded as the designer of the Carden Loyd machine gun carriers and light tanks. Carden decided that the new tank should still have two auxiliary machine gun turrets, like the Sixteen Tonner and the Mark III.23 For its main turret he adopted more wisely a three-man turret similar to that of the A.7 and designed a tank that did not differ from the latter in terms of its 47mm gun main armament, armour and maximum speed, but had the looks of the Sixteen Tonner and the Mark III.
When the prototype of the new tank appeared in 1936 under the A.9 designation nobody seemed to like it. There was a strong case therefore for the development of another tank that would replace the Vickers Mediums, which were becoming obsolete but were still virtually the only gun-armed tanks of the Royal Tank Corps. However, instead of concentrating on the development of a better medium tank, the available engineering resources were split up by a decision to divide tank units into two separate categories.
One of them was to provide close support for the infantry, and in 1934 one battalion of the Royal Tank Corps was separated from the rest and assigned to this role. At the same time Vickers Armstrongs were asked to produce a tank specifically for infantry support. The initial response to this demand was the A.10 tank, which was very similar to the A.9 but had armour up to 30mm instead of 14mm thick and was relieved of the auxiliary machine gun turrets. But although its armour was thicker than that of the medium tanks it was not considered sufficient for the infantry support role. In view of this and the contemporary financial restrictions, Carden proposed a very different type of tank that would be much more heavily armoured and at the same time cheap to produce. The idea of such a tank was accepted in 1935 and led to the A.11 infantry tank, which appeared in prototype form a year later.
The A.11 was a slow, 11-tonne vehicle with a one man turret mounting a single machine gun. Its frontal armour was up to 65mm thick, which put it ahead of most other contemporary tanks, but otherwise it was a throwback to the First World War, conceptually little different from the Renault FT. Nevertheless, it was the type of tank favoured by General Elles, who in 1934 became the Master General of the Ordnance and as such was able to direct tank development. The A.11 was consequently adopted as Infantry Tank Mark I and Vickers Armstrongs proceeded to produce 139 of it.
However, the shortcomings of the A.11 quickly became evident and in 1936 a decision was taken to design a successor to it, which became the A.12 and later Infantry Tank Mark II and which was usually called Matilda. Design of the A.12 was carried out by the Royal Ordnance Factory in collaboration with the Vulcan Foundry and was based on the A.7 mentioned earlier, except that it had no hull machine gunner. Because no sufficiently powerful engine was available at the time in Britain, the A.12 followed the example of the A7E3 version of the A.7 in being powered by two bus-type diesels geared to a common output. It also incorporated novel features of its own, such as dispensing with the angle-iron frame to which armour plates were previously riveted in all other British tanks. Instead its castings and plates were bolted together, thereby saving weight. At 78mm its frontal armour was thicker than that of any other contemporary tank and made it immune to the existing anti-tank guns. The armour made it weigh 26.5 tonnes, which was more than the weight of any British tank since the A.1 Independent, but neither this nor its low maximum speed of 15mph detracted from its effectiveness. In fact, ignoring the limitations of its intended role, the A.12 Matilda was the most successful British tank design of the 1930s.
The one major shortcoming of the A.12 was its main armament, which consisted of a 40mm 2-pounder gun that succeeded the obsolescent 47mm 3-pounder at the time of its development. As a weapon against enemy tanks the new gun was comparable to the best of the contemporary tank and anti-tank guns, but this was achieved by firing solid, armour-piercing shot that was relatively ineffective against anti-tank guns, weapon emplacements and similar targets. What was needed, particularly for a tank that was to support the infantry, was high explosive ammunition, but this was not provided for the 40mm gun, although Renault FT already had high explosive ammunition for its 37mm gun 20 years earlier.
An even better solution would have been to arm the A.12 with a larger calibre, dual purpose gun. A small proportion of the A.12, which were designated ‘close support tanks’, was in fact armed with a 3in. (76.2mm) howitzer instead of the 40mm gun, and this was provided with high explosive rounds, but its main role was to fire smoke shells.24
Another problem with the A.12 Matilda was the lack of experience in the development of tanks and the limited resources of the Vulcan Foundry, which was entrusted with its production because the only experienced producers of tanks, Vickers Armstrongs, were already fully occupied with other work. As a result only two A.12 Matildas were completed by the outbreak of the Second World War.
While the A.11 and the A.12 Matilda were being developed for infantry support, tanks were also needed for the other category of tank units that formed part of the mobile armoured forces. By 1937 these took the form of the Mobile Division, which incorporated the Tank Brigade but was not an ‘all-tank’ formation of the kind Fuller and some of the protagonists of mechanized forces advocated. However, it was not an effective all-arms combat formation either. In fact, it was still considered to be a mobile force for sweeping flanking manoeuvres rather than direct confrontation with the enemy’s main forces. In this respect it could be, and was, regarded as a successor of the cavalry divisions, and its role was limited to that to which horse cavalry was reduced during the 19th century. All this influenced the characteristics of the tanks developed for the Mobile Division and its successors.
The most powerful tanks already being produced for the Mobile Division were the A.9 medium tank, which was re-branded a ‘cruiser tank’, and the A.10, which was not considered to have sufficient armour for an infantry tank and which became a ‘heavy cruiser’ although it was only 1.75 tonnes heavier than the A.9. The A.9 had a maximum speed of 25mph, which was not considered fast enough for the Mobile Division, and this applied even more to the 16mph maximum speed of the A.10. However, in the absence of other candidates, both were adopted for limited production. The first was delivered in 1939 and eventually the number built totalled 295 tanks.25
In the meantime another and more mobile cruiser was developed following a visit to the Soviet Union in 1936 by Martel, who was by then Assistant Director of Mechanization at the War Office. During the visit Martel attended Red Army manoeuvres and became impressed with the Soviet BT tanks and in particular with their suspension.26 It was apparently new to him, although the experimental tank built in the United States by J. W. Christie on which the BTs were based had already attracted widespread interest in 1928 when it set up a speed record of 42.5mph.27 This prompted the US Army to order five tanks from Christie in 1931 and to take over two more ordered by the Polish government, which had defaulted, while the Soviet authorities reacted even earlier by ordering two chassis in 1930. However, it was only eight years after the appearance of Christie’s high speed tank that Martel took note of it and proceeded to advocate the development of a cruiser tank based on it. To speed this up, Martel arranged the purchase of a vehicle that Christie still happened to have by the Morris car company, and its head, Lord Nuffield, undertook to develop the new cruiser tank.28 A new company called Nuffield Mechanization was set up for this purpose with the approval of General Elles, who was still Master General of the Ordnance and who wanted to create competition for Vickers Armstrongs, who until then enjoyed virtual monopoly in the production although not in the design of tanks.29
Nuffield Mechanization worked with remarkable speed and, although they had not produced tanks previously, built the first prototype of the new tank within 12 months of receiving an order for it. The tank, which was designated A.13 and later Cruiser Tank Mark III, was very different from Christie’s tanks. In particular, it had a very different and much more sensible configuration similar to that adopted earlier for the A10E1 version of the A.10 and almost simultaneously for the A.12 Matilda. The only thing in common with Christie’s tanks apart from the suspension was the Liberty engine, a First World War American aircraft engine whose production was revived by the Nuffield organization. This V-12 engine developed 340 horsepower, which made it more powerful than any engine available for British tanks since the A.1 Independent of the mid-1920s and provided the A.13 with a high power-to-weight ratio of 24hp per tonne. As a result the A.13 was faster than all earlier British medium or cruiser tanks, having a nominal maximum speed of 30mph and in practice being capable of almost 40mph.
The armour of the A.13 cruiser was still no thicker than that of the Sixteen Tonner or Carden’s A.9, but its maximum thickness was doubled to 30mm on the second version. The need for heavier armour led to the idea of a ‘heavy cruiser’, which originated with the A.10, and the design of two different versions of such a tank was ordered in 1938. One of them, the A.14, was designed with the co-operation of the London, Midland and Scottish Railway (LMS) company and the other, the A.16, was designed by Nuffield Mechanization. They differed in engines, transmissions and suspensions but their general configuration was the same, and in addition to the main turret both had two auxiliary machine gun turrets, like the Sixteen Tonner, after which those who ordered them apparently still hankered.
The maximum thickness of armour of the A.14 and A.16 was 30mm, which by the time they were built was not more than that of the second version of the A.13. They did not, therefore, offer any advantage so far as armour protection was concerned, nor were they better armed as their main armament still consisted of a 40mm gun. In consequence the development of both was, very sensibly, abandoned.
However, when the A.14 was abandoned LMS were asked to design a simpler cruiser tank with the same layout and Christie suspension as the A.13 but with armour up to 40mm thick. This tank was called Covenanter and had a special, 12-cylinder horizontally opposed engine and a significantly lower silhouette but was still armed with a 40mm gun. Nuffield Mechanization designed its turret, but instead of participating in its production offered in mid-1939 to design their own version of a ‘heavy cruiser’ from the basis of the A.13 and using the Nuffield Liberty engine. The offer was accepted and in August 1939, just one month before the outbreak of the Second World War, an order was given for the production of the tank, designated A.15 and later called Cruiser Tank Mark VI Crusader.30 The A.15 resembled the Covenanter but was larger and somewhat heavier, weighing 19 compared with 18 tonnes. It was armed with the same 40mm gun as the Covenanter and, showing how hard old habits die, it still had one auxiliary machine gun turret, which resulted in it having a crew of 5.
The eight medium and cruiser tanks developed between 1934 and 1939 differed from each other in several respects except for their main armament, which in all cases consisted of the same 40mm 2-pounder gun. This showed that, by comparison with all the effort devoted to the development of engines, transmissions, suspensions and other components, little attention was paid to the development of more powerful armament. In particular, no attempt was made to arm any of the medium or cruiser tanks with a dual purpose 75 or 76mm gun comparable to those mounted in medium tanks that were being developed by then in at least two other countries.
To be fair, in some of the medium and cruiser tanks the 40mm gun was replaced by what was originally called a 15-pounder mortar and then a 3.7in. (94mm) howitzer and later by a 3in. (76.2mm) howitzer. But these were limited purpose weapons intended primarily to fire smoke shells, as already mentioned in connection with the Matilda infantry tank, although they were also provided with some high explosive rounds. However, they were not provided with armour-piercing ammunition. They were not therefore comparable to the dual purpose 75 or 76mm guns mounted in Soviet and German tanks with which they were often wrongly equated.31 The latter were, admittedly, short-barrelled low-velocity weapons, but they could still knock out contemporary tanks, if only by smashing their relatively thin armour by the sheer mass of their projectiles. At the same time they could effectively engage anti-tank guns, machine gun emplacements and similar targets with high explosive shells.
The lack of medium calibre dual purpose guns did not seem to concern those involved with the development of British medium and cruiser tanks, who thought more in terms of sweeping mobile manoeuvres rather than of fighting hostile armoured forces and, even less, of engaging in all phases of offensive operations. In consequence, they only expected tanks to be armed with ‘one small gun and several machine guns’, to quote a contemporary opinion.32 Such views contributed, among others, to the repeated attempts to develop tanks with additional machine gun turrets. As to the calibre of tank guns, a 1937 Tank Brigade report endorsed by the General Staff stated emphatically that a gun larger than the 40mm 2-pounder was not required.33
To make matters worse, the 40mm gun was not provided with high explosive ammunition with which it could engage unarmoured or ‘soft’ targets with some degree of success. In contrast to the corresponding 37mm tank guns used in other countries, the only ammunition provided for the 40mm gun was solid shot, which was good at perforating the armour of the opposing tanks but not against other targets.
The effectiveness of the 40mm guns and of the earlier 47mm guns was reduced further by the adoption by the Royal Tank Corps of the practice of firing on the move, which kept up the tactical mobility of tanks and at the same time emulated the warships that served as their model. In fact, the influence of warships on tank gunnery extended from the adoption of naval training devices to the performance in at least one of the tank training exercises of the classic naval gunnery manoeuvre of ‘crossing the T’ (that is sailing in line across the path of the enemy fleet to bear the maximum number of guns on it), although the relevance of the latter to tank warfare was doubtful.34 Some rightly questioned at the time the ability of tanks to fire accurately when moving over rough ground.35 However, in spite of this, firing on the move instead of at the halt continued to be favoured, but it was only after the Second World War, when stabilized gun controls were developed, that it became effective.
An entirely different aspect of the development of tanks in Britain was that of the light tanks. It originated with the ideas that emerged after the First World War about the use of very light armoured vehicles to help the infantry advance in the face of opposition. Very similar ideas had already led to the development in France of the Renault FT light tank, but what began to be considered in Britain during the early 1920s were even lighter vehicles. To further the development of this kind of vehicle, Major Martel built in 1925 in his own garage a very light one-man half track. This was followed by an enlarged two-man version, eight of which were built by Morris Motors for use by the Experimental Mechanized Force in 1927.36
Interest aroused by Martel’s vehicle encouraged another private venture, which was the construction of a one-man wheel-and-track vehicle by J. Carden and V. Loyd, who were then running a large garage in London. Their original vehicle was enlarged into a tracked two-man version, and eight were also ordered for the Experimental Mechanized Force.
After the 1927 trials it was decided that what was needed were two different types of light tracked armoured vehicle. One of them was a fast turreted reconnaissance or scout vehicle for use by the tank battalions of the Royal Tank Corps. The other was an open-top machine gun carrier for use by the infantry. By 1928 Carden responded to these requirements by designing the Carden Loyd Mark VII light tank, a 2.5-tonne two-man vehicle with a turret mounting a machine gun, and the Carden Loyd Mark VI, a small low silhouette two-man machine gun carrier weighing about 1.7 tonnes.
The Mark VI led eventually to the development of the Bren Gun Carrier, which the British Army used on a large scale during the Second World War. During the 1930s several other armies also adopted versions of the Mark VI with head covers or a raised and enclosed superstructure as ultra light weight low-cost light tanks. However, their capabilities were extremely limited and they could only be justified as training machines.
On the other hand, Carden Loyd Mark VII became the forerunner of a series of Vickers Carden Loyd light tanks, which came to be the most numerous British tanks after the mid-1930s and commercial versions of which were sold by Vickers Armstrongs to several countries. They were mechanically successful, being relatively reliable, and capable of speeds of up to 35mph, and together with the Mark VI they earned their designer, who became Sir John Carden, the high reputation mentioned earlier. But their fighting capabilities were restricted by their armament, which in most cases consisted only of a single rifle calibre machine gun. This might have been adequate for policing the North West frontier of India, where some of the light tanks were employed, but it was ineffective even against other light armoured vehicles.
It was also realized, in contrast to the attitude that prevailed in France, that the one-man turrets of the original Vickers Carden Loyd light tanks expected their occupants to perform too many tasks, particularly in rapidly changing mobile operations. In consequence, Light Tank Mark V, which was introduced in 1934, was provided with a two-man turret that enabled the functions of the tank commander and of the gunner to be separated so that they could operate a tank more effectively. Mark V and the very similar Mark VI were also armed with a Vickers 0.5in. (12.7mm) heavy machine gun in addition to the usual 0.303in. (7.7mm) rifle calibre machine gun. But no significant improvements were made to the chassis, which remained much the same as that of the Mark IV, with the result that the larger turret made the marks V and VI top heavy, looking as if they would topple over at the slightest provocation. Martel rightly argued at the time that the Mark VI was too short, which implied that it did not have sufficient length of track on the ground for a good ride over rough terrain, and that it was overloaded.37 Nevertheless, a 1936 memorandum by the secretary of state for war claimed that the Mark VI was ‘superior to any light tank produced by other nations’.38 Moreover, light tanks kept being produced and by the outbreak of the Second World War the number built had risen to 1,002.39
In fact, the Mark VI was inferior in several respects to light tanks being produced elsewhere. One of them was the L.60, a 7.5-tonne tank developed by 1934 in Sweden by the Landsverk company with the help of German engineers, which was armed with a 20mm cannon and specimens of which were sold to Austria, Hungary and Ireland before it was developed further for the Swedish Army into the Strv m/38 armed with a 37mm Bofors gun. By 1935 the Czech company Ceskomoravska Kolben Danek also started producing 50 TNH light tanks armed with 37mm guns for Persia (now Iran), which became the forerunners of the TNHP tanks taken over by the German Army in 1939 and used by it successfully as PzKpfw 38(t) during the early stages of the Second World War.
What is more, as early as 1928 Vickers Armstrongs brought out a tank armed with a 47mm gun and a coaxial machine gun, which they designed on their own initiative prior to taking over Carden Loyd Tractors and the light armoured vehicles that the latter were developing. The tank was the 7.4-tonne Type B version of the Vickers Six Ton Tank, which had a single two-man turret in contrast to the Type A version that had two side-by-side one-man machine gun turrets, like some of the early armoured cars. The 47mm gun of the Type B was short barrelled but of the same calibre as the guns of the Vickers Medium tanks, the Sixteen Tonner and all the other British medium tanks up to the original version of the A.9. Because of it Type B was greatly superior in terms of gun power to all the Vickers Carden Loyd light tanks. At the same time its armour protection was similar to that of the contemporary medium tanks and its production cost was considerably lower. Development of this type of tank might therefore have been a better investment for the British Army than all the multi-turreted medium tanks or the light tanks armed only with machine guns, particularly at a time of financial stringency that is often blamed for the shortage of well-armed British tanks on the eve of the Second World War. In fact, the British Army did consider it only to reject the Vickers Six Ton Tank, apparently because of its slow-motion double bogie suspension.40
However, rejection of the Vickers Six Ton Tank by the British Army did not discourage eight other armies from buying it. One was also borrowed by the US Army and after being tested at the Aberdeen Proving Ground was virtually copied in 1932 as the T1E4 experimental light tank, which represented a major step forward in the development of US light tanks.41 This eventually led to the M3 or Stuart light tanks, which the British Army was glad to receive from the United States in 1941.
Two of the armies that procured Vickers Six Ton Tanks went further and produced copies of them in quantity. One was the Polish Army, which bought 38 Six Ton Tanks in 1931 and subsequently developed an improved single turret version armed with a 37mm Bofors gun, 120 of which were produced by the outbreak of the Second World War.42 The other was the Red Army, which in 1930 signed a contract with Vickers Armstrongs for the delivery of 15 Type A tanks, copies of which began to be produced in the Soviet Union as T-26 tanks a year later. As many as 1,626 were built by 1934 but production was then switched to the single turret model, which was armed with a 45mm gun and was obviously much more effective. By the outbreak of the Second World War in 1939 the total T-26 models that had been built rose to about 8,500, making Vickers Armstrongs’ Six Ton Tank in Soviet guise the most numerous tank at the time in the world.43