12 December 1936. 15:00hrs. Newcastle-Upon-Tyne. England.
Colonel Justice Tilly, as Chief Instructor of the Royal Tank Corps at Bovington Camp, had been invited to come and inspect the work that was being done on the tanks that his trainee tank men would be working on in the future.
The Mark VI light tank, and its predecessors, were well known to the RTC, the latest model, the VIB had a few improvements over the Mark V and the Mark VIA, but still suffered, in Tilly’s mind with being top heavy and really only good for reconnaissance. The conversion of the cavalry regiments, for whom reconnaissance was one of their specialities, the tank was adequate. However, for screening and exploiting, the other two cavalry specialities, the two machine guns (.50 and .303 Vickers) were limited at best. The increase of armour to 14mm in the light tank suggested that the days of using a heavy machine gun against an equivalent vehicle was fading fast. What worried Tilly more was that it wasn’t only the mechanised cavalry regiments that were being equipped with the light tank. As these were the only tanks in full production all too many were ending up in the hands of people who needed a proper tank capable of taking on another tank.
He had been pleasantly surprised that when the Mark VI had been sent to Bovington a couple of Vickers employees had been sent down with it to help sort out the driving and maintenance manuals. This had helped speed up the process of making some changes to the production models which had improved some of the simple things that would make life easier for the soldiers fighting and maintaining the vehicle.
Next on the tour was the A9E2 which was at an advanced stage of its build. He’d seen the A9E1 at Farnborough, and was glad to see that the E2 had taken on board some of the criticisms of its predecessor. It looked like the new layout of the suspension would overcome the problems of it bouncing all over the place. Losing the two forward machine gun turrets gave the tank a better balance. The AEC engine that replaced the Rolls-Royce Phantom was also judged an improvement. Though to Tilly’s mind it only took the tank to its new limits of speed and armour, as the power didn’t have any spare capacity should the tank need to be upgraded again. He also took the chance to speak to the Vickers team about the tracks. The idea of ‘lubricated tracks’ was all very well in theory, but if there was one thing that tank crews hated above all was having to try to re-attached tracks that broke or threw themselves off the suspension. Being clever with tracks wasn’t about making them more complicated, it was much more about making them trustworthy and practical. He was happy to see some nods of agreement from his hosts.
His basic problem with the A9 was where it fitted into the scheme of things. The idea that was being floated around of ‘cruisers’ had come from a lecture Fuller had given which used naval categories to describe tanks types. The origin of this thinking went all the way back to the ‘Land Ship’ committee that had given birth to the tank in the first place. Tilly wasn’t impressed with the notion. If the A9 was to take its place in the army if fell between the stool of being a light reconnaissance tank like the Mark VI and a medium tank. Tilly was of the opinion that what was needed was a new and improved medium to replace the old Mark IIs that were obsolete. The Medium Mark IIIs and the A6 and A7s seemed to be going nowhere as far as Tilly could see, and the Vickers men nodded in agreement again.
In Tilly’s opinion creating a tank of around 7 to 10 tons wasn’t going to be big enough to do the job the RTC needed. Just about everybody was happy enough with the 2-pdr gun, as an anti-tank gun replacing the old 3-pdr, and the promised 25mph was impressive. It left the problem, like the Mark VI that it relied on speed rather than armour to keep it out of trouble. If the British army was introducing the 2-pdr as an anti-tank gun, then no doubt everyone else would have something in the 37-47mm range as their own AT gun. Having armour only of 14mm to protect it seemed ludicrous. While the E2, with the weight saving of losing the two turrets and one gunner meant that some more armour could be fitted around more vulnerable spots, Tilly still thought it was too little.
Which brought them to the A10E1. This prototype was due to be displayed in the Spring and Tilly was the first man outside of Vickers to have a good look at it. The decision had been taken to make two models initially, the difference being in the engines. The first was as specified, a single AEC bus engine, the same as in the A9. Since the A10, would weigh something like 14 tons fully loaded, the design team were sure that, like the underpowered A9E1, this would be just as unsatisfactory. With 30mm of armour it was a bit more like what Tilly was arguing for, but it would lose the kind of speed that the A9 promised. That was why Vickers was making the second model. There had been a lot of debate amongst the design team about this. The company managers, aware of costs, wanted to look at simply creating a double AEC engine. By putting two engines in, it would theoretically double the power available. However, it posed a fairly serious engineering challenge. Working out how to keep the two engines working harmoniously would be difficult and probably would be a nightmare in the field. With this Tilly strongly agreed.
The second prototype was going to be a bit longer than the first, 19 feet like the A9, needed because the engine was one of the Rolls-Royce Eagle IXs that had been acquired. No one was suggesting that this was what would actually be the engine of choice, it was out of production, but it would answer the question of whether an aero-engine could be used to power a tank, giving it the kind of power to weight ratio required. A third choice had also been suggested which was the original idea in the old A6 specification was to use a Thornycroft RY 12 marine engine developing about 500hp.
The question that Tilly immediately asked was about the range these tanks would have. He could only imagine that either of these powerful beasts would be thirsty creatures. A tank that had to stop every hour to be refuelled wasn’t going to be much use to anybody. He was informed that the A9 was rated for about 120 miles radius of action on roads. The A10 with the same engine would be a bit less, with the bigger engine, and bigger size, allowing a larger fuel tank, it was hoped the radius would be nearer 140 miles. There were too many ‘maybes’ and ‘hoped for’ in that answer for Tilly’s ease of mind. At least they knew that the longer a tank could be in action with enough fuel and ammunition, and crew that weren’t terribly inconvenienced by cramped and difficult conditions within the tank, the better. It that lesson hadn’t been learned from the early days of tanks in 1916-18, then they should all give up and go home.
Talking of tanks from the days of Cambrai and the 100 days, they came to the A11E1. Progress on the E2 was still in the early stages. Tilly had seen the A11’s demonstrations at Farnborough and wondered about what had happened to the last twenty years. If it sat beside a Whippet tank it wouldn’t look as if much progress had been made at all. At this point Sir John Carden joined the group and invited Tilly to join him when he’d finished the tour of the plant, there were a couple of questions that he’s like to ask him. Tilly was happy to oblige and it seemed a good time to have a look at the drawings for the A11E2 that Carden had in his office.
The two men had met before on a couple of occasions and had many mutual friends and acquaintances. A couple of pink gins arrived and Carden showed him what he hoped was a slightly more acceptable infantry support tank. He wanted once more to replace the Meadows engine which the AEC bus engine, providing the A11 with a bit more power again. Putting in 135hp rather than 88hp would propel the tank at something more than a cross-country runner’s pace, even with the bigger turret’s weight. Tilly liked the idea of the 40mm semi-automatic gun. Supporting infantry was something that an HE shell would be better at than simply a machine gun. With the pink gin loosening the inhibitions, that gave Carden the chance to ask one of his outstanding questions.
It seemed to him, looking at the direction the War Office were going that the A11 and A12 specifications for infantry support tanks, well protected themselves, but carrying only machine guns or the 2-pdr. The old Great War machines, at least the males, carried a six pounder to deal with well protected defences. Surely there was an argument for a gun that could provide a reasonable HE capability? To Justice Tilly’s mind, Carden was straying into what many regarded as heretical thinking. The fight to keep the Royal Tank Corps alive, when the Machine Gun Corps had been suppressed after the war, meant that doctrine about the right use of tanks had become not dissimilar to Christian doctrine. There was orthodoxy and heresy, and quite a few popes in the tanking fraternity who wouldn’t be slow to condemn the heretics.
The example cited by Carden was that he was meant to design two different turrets for the A9 and A10, one carrying the 2-pdr and another for Close Support tanks that was to be fitted with the QF 3.7inch howitzer. This fired a half-decent 20lb shell, but with limited range, and as Carden understood it, was really only used to fire off smoke shells. Colonel Justice Tilly, as Chief Instructor at Bovington, felt he had to defend the orthodoxy. Tanks, with the exception of the light reconnaissance machines, were to fight tanks, whether in support of infantry being attacked by tanks or in manoeuvre warfare. What counted was the ability to defeat enemy armour. If fixed defences were a problem, then the artillery would be called on to suppress it, the infantry overcome it, and the tanks would then exploit the gap.
Carden noted that this wasn’t quite the same as the 100 days offensive at the end of the Great War. There the combined efforts of all, infantry, artillery, tanks, and even aircraft, were utilised together to defeat the Germans. This seemed to have given way to Fuller’s navy battles on land, where light units, like destroyers sniffed out the enemy, then the cruisers were the fast and hard hitting force, backed up by battlecruisers or heavy battleships. The War Plan of 1919 had never been put to the test, and Carden wondered if the Russians, French or even Germans were playing from the same textbook.
What amazed Tilly was that Carden then brought out a sketch book. He admitted looking at the A12 specification that Vulcan Foundry were working on and wondered what his own notion might be. He had drawn up some ideas. Fundamentally he had taken the A10 to its logical conclusion. He had one drawing with the current suspension, another using Horstmann’s system. Powered with an engine producing 500hp, it would have to grow beyond the current limitations of rail transport. A wider body would allow a larger turret ring, which would give the possibility of having a bigger gun than the currently sufficient 2-pdr.
According to Martel’s report from Moscow, the Soviet T-28 was armed with a 76.2mm howitzer. There were two British 3-inch guns which provided the same calibre. There was howitzer and an anti-aircraft gun. The 3-inch anti-aircraft gun was being replaced by the newly designed 3.7-inch gun, meaning that the 3-inch 20 cwt AA gun was going to be surplus to requirement. Carden reckoned he could knock a fair few cwt off a tank mounting, but the turret would need to be pretty large. The muzzle velocity and the size of the shell would be a match even for the big new French tanks that were starting to appear. It might cause some problems for the gunner, but it could easily take an anti-tank round as well as the HE round it was designed for. The Ordnance QF 3-inch howitzer was developed from the QF 13-pdr of Great War vintage. Both these options would require a very big turret, and that was probably some way off the War Office’s list of requirements.
Which brought Tilly and Carden to another set of drawings. In this case he was looking for an intermediate solution, and he had looked to the past for inspiration. The 6-pdr gun on the male Mark I tanks had started life as a naval gun, and Vickers and Woolwich still have the capability to manufacture guns in 57mm. The early tank 6-pdr gun was a cut down version, L23 barrels compared with the naval L40 barrels. A modern version would surely provide tanks with a gun to replace the 2-pdr. If the A11 and A12 were anything to go by, to say nothing of the French tanks, then more powerful guns were going to be needed, and if they were capable of firing both a good anti-tank and HE shell, then so much the better, surely? If that was the case, then it may well be necessary to design a follow on to the A10 which would have more than the 60-70mm armour of the A11 and A12, with a big enough turret ring to mount bigger guns as they came along. 500hp engines might need to grow too, and it certainly seemed the way things were going in the aero-engine sector, more and more powerful engines were being designed for aircraft to fly faster and carry more load.
So, the drawing that he had spent the most time, going from the detailed drawings was the an A10, lengthened and widened, a raised engine compartment for the bigger engine, around a 60-inch turret ring, and a long barrelled 6-pdr gun. Tilly noted the figures of 80mm armour on the front and turret, 70mm on the sides, an overall weight of around 20 tons. The turret was wider, bulging outward to provide more elbow room presumably. He noted that the gun was on an external mantlet. Another heresy was hidden here. British tank gunners fired on the move. A large part of the training was RYPA, Roll, Yaw and Pitch Apparatus, not unlike their naval cousins dealing with all the movements of a ship at sea. The traverse mechanism of the turret was matched by an elevation controlled by the gunner’s shoulder, and therefore of the steadiness of the ride of the tank was important. The gun had to be finely balanced about the trunnions, meaning that a greater inboard length of the gun. An external mantlet meant that Cardin was designing a geared elevation system for his improved A10.
When asked about it, Carding simply remarked that the Close Support 3.7-inch howitzer required the geared elevation. It simply meant that a larger gun wouldn’t be able to be manipulated by the gunner’s shoulder, therefore it made sense to put the balance further forward, allowing more space in the turret for gun recoil and ease of loading. Surely firing from a stationary position was more inherently accurate than firing on the move? Besides, if war came and a great many new trainees were to become tank gunners how much time and effort on RYPA would have to put into that training compared with learning a much simpler geared elevation coupled with the traverse system? Tilly found himself grinding his teeth, this man would need to be kept far away from Percy Hobart.
Another pink gin later and Carden showed off some more of his flights of fancy as he called them. Using the same basic platform of the improved A10, Carden had tried to imagine how the new artillery piece, the 25-pdr might be conveyed like the old Birch gun system. It seemed odd, but he had reversed it, so that barrel was over the engine compartment at the rear. Instead of a turret, the gun and its crew would basically fill the fighting compartment, and the sides of the tank would be built up to give them some protection against counter-battery fire. He had a few ideas about improving the notion of the universal carrier, using the Dragon tractor as a basis for carrying a squad of infantrymen under the shelter of steel following their own artillery closer than possible if walking, and falling on the enemies’ positions before they could react. In another drawing he had an anti-aircraft gun mounted on a tracked base. These were all ideas that Tilly recognised from the various permutations of the Experimental Mechanical Force and wondered whether he’d see the possibilities that had engendered brought to birth. Carden’s drawings suggested that it might just come about, God and His Majesty’s Treasury allowing.
