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WW2 British Tactics

Operation Sentry – The First Centurion Trials 1945

Nation Flag IconUnited Kingdom (1945) 6 tanks used in testing

New tanks need to be designed, tested, and deployed carefully. Even with the pressures of war taken into account, the process should be methodical to ensure that mechanically reliable vehicles with good fighting characteristics and survivability get to the front line. The United Kingdom, in particular, had by 1945, suffered terribly economically, industrially, and with the bombing of its civilians during World War 2. This, combined with the need to produce a large number of tanks to field against the Germans and their allies, had all contrived to hinder the design and production of new tanks. In particular, by 1943, there was a desire to have a good cruiser tank, well protected and fielding the excellent 17 pounder gun. The much-delayed project was finally ready by 1944 and passed initial domestic trials. However, this new vehicle, the A.41 ‘Centurion’ could also be sent to mainland Europe for active trials in a war zone. The object of these first foreign Centurion trials was, therefore, to make use of the considerable battle experience of crews available in British forces in Europe and to conduct real-world trials under as near to combat conditions as possible.

The A.41 Cruiser Tank ‘Centurion’ had started life in October 1943 with a requirement for a 45-ton tank with a 650 horsepower engine, well sloped frontal armor, and carrying the new and powerful 17 pounder gun. Effectively, this would create a vehicle at least equal to the German Panther tank. When this tank was finally ready, the war in Europe was all but over. With some fighting still taking place there, it became a rush to get this brand new tank to Germany perhaps in the hope of some action. Even if it could not, the tank would be operationally deployed and the experience gained in a war zone would be invaluable in improving it. What this tank became was perhaps the finest tank ever made – the British Centurion, a tank in service for decades after the war, with hundreds of variants seeing combat around the globe.

Development

It was not until February 1944 that the final specifications for what the as-yet-unnamed A.41 Heavy Cruiser Tank (it would not be known as ‘Centurion’ until later – at this time, the name ‘Centurion’ was still being touted for the A.30 – the tank which would be known as ‘Challenger’) would look like. With those requirements set, it was planned to produce 20 pre-production prototypes in order to conduct evaluation trials.

In May 1944, the Director of the Royal Armoured Corps (D.R.A.C.) amended the order for 20 of this first pattern of A.41, so that small features could be evaluated. These included the choice between a 20 mm Polsten cannon and 7.92 mm BESA as a turret machine gun, or even a 77 mm gun (as fitted to the A.34 Comet), and a rear escape hatch vs rear facing BESA machine gun.

The first A.41 prototype, ‘P1’, armed with the excellent 17 pounder gun and a 20 mm Polsten cannon fitted in a separate mount on the left of the unusually shaped turret.
Source: Pinterest

Technical Details A.41 P Series

The requirement for well-sloped frontal armor also meant that the idea of the vertical driver’s plate on the front of the tank, so recognizable on British tanks from the A.22 Churchill to A.34 Comet, was gone. This had been kept partially to make sure a hull-mounted machine gun could be retained for the tanks, but with only a single crew member in the hull and this single sloping front plate, this hull machine gun was finally removed.

A single large front sloping plate on the A.41 would make it look more like the German Panther, with the exception that, whilst that German tank had 80 mm or more of armor on the glacis, this A.41 had just 2.25” (57 mm) across the glacis and nose plate. Whilst this may seem like a problem, it is perhaps noteworthy that, although the Panther had more armor than the A.41, it would still be easy to penetrate by the 17 pdr. at any normal combat ranges, just as the A.41s would be vulnerable to the 7.5 cm KwK 42 gun of the Panther in return. However, production A.41 ‘Centurions’ would adopt a thicker glacis to more closely resemble the Panther.

The suspension was in the form of 6 doubled rubber-tired bogie wheels on each side, with the return of the 20” wide (508 mm) wide, 5.5” (140 mm) pitch track supported by rollers. The 108 links for the track on each side of the tank were made from cast manganese steel and were not fitted with rubber pads. The track and suspension were also usually hidden under a 6 mm thick ‘bazooka plate’ running the full length of the suspension. Each bogie was provided with a Newton-Bennett shock absorber and a coil spring and a hydraulic damper.

Powered by the Rolls Royce Meteor Mk.4A petrol engine delivering 635 hp at 2,550 rpm, it had a power to weight ratio of 13.7 bhp/ton (Imperial), which was only a problem in terms of fuel consumption. The 120 gallon (545.5 liters) petrol tank was only sufficient for 90 miles (145 km) of travel on a road. This meant the A.41 consumed some 1.3 gallons (6.1 liters) of petrol per mile (3.8 liters of petrol per km).

The 7-speed (5 forward and 2 reverse) Merritt-Brown Z51 gearbox combined with Girling brakes allowed for the steering of the tank under what was known as a ‘controlled-differential’ system. This was the preferred solution for a tank transmission, but it was decided to also try the Synchromesh Self-Shifting (SSS) system as well. Known as the Sinclair-Meadows Powerflow SSS system, this was a 7-speed (4 forward and 3 reverse) automatic gear change system by the Hydraulic Coupling and Engineering Company. This was an advanced and complex gearing system that had been experimented with during the war perhaps most famously on the TOG tank program. It offered the enormous advantage of allowing for a smooth transition from forward to reverse motion and vice versa via a fluid fly-wheel clutch.

On the A.41, the SSS system allowed for the tank to reverse at speeds of up to 14 mph (22.5 km/h), but only one A.41 was ever fitted with this system and was designated A.41S. The system was eventually abandoned after a series of minor problems and unpopular reports on it from the crews, for whom it was too different from what they were used to. The Merritt-Brown Z51 would eventually be the winning system from these trials.

Domestic Trials

Early domestic trials were, by all accounts, a pleasant change from many tanks during the war, where problems followed problems. The first automotive trials had actually taken place in September 1944 using that ‘soft-boat’ (the term for a non-armored steel test hull). Then, the only particular problem observed was excessive tracking to one side, which caused a lot of undue brake wear. There were no fundamental problems with the design and it immediately received a green light for the production of prototypes which were to start in January 1945. However, with every possible effort being pushed towards the D-Day landings (Operation Overlord) set for summer 1944, the production of A.41 could not start straight away. It would not actually be until April 1945 that the first prototype A.41, now designated as a ‘Heavy Cruiser’, was actually finished at Woolwich Arsenal. This first vehicle was delivered to the Fighting Vehicle Proving Establishment (F.V.P.E.) at Chertsey, Surrey, and immediately started a series of automotive trials. It was followed shortly thereafter for trials at Chertsey by the next two vehicles. The story for all three was the same – they were deemed excellent.

Pilot vehicle number 1 blew through its tests, covering over 1,055 miles (1,698 km) with 467 miles (752 km) of those off-road. Reaching a top speed of 23.7 mph (38 km), this brand new 45.5 ton (46.2 tonnes) tank was an impressive vehicle. By the end of May 1945, a 4th pilot vehicle arrived and this was sent for gunnery trials at Lulworth and this too went very well. In fact, by this time, the only notable criticism of any note was that the 20 round forward ammunition bin needed to be modified slightly.

To Europe

With domestic trials proceeding perhaps better than could have been expected and with the war going well, it was decided to send them to the front in Europe for evaluation by combat units. The plan for this evaluation was ‘Operation Sentry’ and had actually been proposed even before the first domestic trials had even taken place, such was the confidence in this vehicle. With such excellent initial results, there was no reason not to go ahead with it.

The first Centurion prototype with the powerful 17 pounder gun as the main armament and the distinctive mounting of a 20 mm Polsten cannon as the secondary armament next to it. Note that this turret is only made of mild steel and not rated as armor, as denoted by the small triangle in the middle of the left side of the turret.
Source: IWM

Of the 20 of this pre-production batch of A.41s ordered, 6 of them were to go on Operation Sentry. Three would be selected from Woolwich Arsenal (Royal Ordnance Factory, Woolwich), specifically P.3, P.9, and P.11. Three more would come from those produced by Royal Ordnance at Nottingham, specifically P.4, P.6, and P8.

Originally, it had been desired to test them with crews drawn from the Grenadier, Coldstream, Welsh, and Irish Guards regiments, so that they could be put into combat against the remaining elements of the German Wehrmacht. However, the remaining German military forces in northwest Germany, Denmark, and Holland surrendered to the British on 4th May, followed on the 7th by the signing of a full formal surrender of all remaining German forces to come into force the next day.

The war in Europe, therefore, came to an official end on 8th May 1945 with the surrender of all German forces to the Allies, although small pockets of forces remained to be collected. For all intents and purposes, the War in Europe was over and Germany had been utterly defeated. For the British, this had marked the culmination of a long and hard-fought war that had started nearly 6 years earlier and virtually bankrupted the Empire. It also marked the end of any prospect of getting the new A.41 into combat against the Germans.

There was, however, still a substantial number of vehicles and men in Europe, and all of the paraphernalia and restrictions of an active war zone. Thus, with the basics of the tank proven solid, these six tanks were quickly assigned to crews from 5th Battalion Inniskilling Dragoon Guards (5 I.D.G.) and 5th Battalion Royal Tank Regiment (5 R.T.R.), all part of the Guards Armoured Division. These were experienced units. 5 I.D.G., for example, had been in action in Europe since July 1944, fighting through France (Liseieux, 23rd August 1944), Belgium (Ghent, 5th September 1944), and into Germany (Rhine crossing, 25th March 1945) reaching Hamburg by May 1945. Trials would be split with 5.I.D.G., operating the tanks from 31st May to 11th June and then taken over by 5.R.T.R. from 12th June to 23rd June.

These crews trained on the tanks in the UK, having been brought back from the European Theater of Operations (ETO) specifically to do so. These were combat-experienced crews and they would be supported by personnel from the Royal Electrical and Mechanical Engineers (R.E.M.E.) who had been assigned to and working at the F.V.P.E. The entire test and evaluation team was then deployed to Germany as part of the 7th Armoured Division.

Note the folded-down driver’s windscreen on the glacis and the unusual configuration of the headlamps, with one above the other vertically on the center-line of the glacis.
Source: Imperial War Museum
The clean lines of the A.41 Centurion belied its power as a tank and it was, without a doubt, the finest British tank produced during WW2.
Source: Pinterest
The turret as used on the A.41 during these trials featured a large front casting, with the distinctive hollow chin at the front to prevent jamming due to a shell strike on that area. The rest of the turret was made from welded steel plates and the front casting was then welded to them. Traversable electrically (Lucas) or by handwheel, and using a 74” (1,880 mm) ring, this turret allowed for 20 degrees of vertical gun movement and 12 degrees of gun depression.
Source: Dunstan

Itinerary

The six Centurion tanks were collected from Lulworth at noon on 13th May 1945 and immediately set off for the port of Southampton. They arrived at No. 20 Transit Camp in the evening. The next morning, they were embarked on Landing Craft Tank (L.C.T.) 798 and 1035 commanded by Lieutenant. C. D. Mitchell and Sub Lieutenant M. F. Bowe, respectively.

On Tuesday, 15th May, the L.C.T.s set sail from Southampton, but stopped overnight at Newhaven and Deal before arriving at Ostend and then finally Antwerp on the evening of the 18th. Disembarking on the 19th, they underwent two days of inspections, including final drive checks on vehicle P.11 before a road march to Nijmegen, a distance of 142 km.

By the 23rd, when they stopped overnight at the town of Brunen (77 km from Nijmegen), the tanks had covered 224 miles on the continent and the road march continued despite the wet weather, with overnight stops at Osnabruck on the 24th and Brentwede on the 25th. They remained there for two days until, on the 28th, the rain finally relented and they set off once more. This time, the drive took them to Hollendstedt, a distance of 80 miles (129 km), where again they stopped for two days. Finally, on the 30th, they left Hollendstedt and did a single 84 mile (135 km) road march to Gribbohn, arriving in the evening. During this transit from the UK and the road march through Holland, just two problems had occurred and both were gearbox failures. The first had taken place before the tanks had even started off at Lulworth and was likely a problem of manufacture. The second, over 700 miles (1,127 km) later, was just 40 miles (64.4 km) outside Hamburg. Other than that, maintenance had been straightforward, apart from a single quill shaft on an auxiliary engine failing. Nonetheless, all of the faults for all of the tanks were carefully logged.

Having arrived safely with little problems, the vehicles underwent their unit trials, followed, between 27th June and 14th July, by live-firing trials at the ranges at Lommel, Belgium. Other trials were then carried out, with the tanks simulating combat attacks and tactical movement – all of which went well.

One of the first batch of prototype Centurions, probably P1. The turret, seen without stowage boxes, can be seen to have very simple and clean lines. The text on the upper rear of the right side skirting plates is simply stating that anti-freeze had been added to the tank’s cooling system. Note the outline of a circle on the back of the turret, where a mounting for a rear-facing BESA machine gun was proposed and thankfully later abandoned.
Source: Dunstan via IWM

Centurion P.3 (W.D. Index Number T.352412) showing its 20 mm Polsten cannon and a stowage box fitted to the back of the turret.
Source: Pinterest
The cast front of the original turret is more apparent when viewed from the right. This is vehicle P.3. Source: Pinterest

A.41 ‘Centurion’ P.8. (W.D. Index Number T352415) with a large box-type structure fitted to the front left of the turret. This was a prototype of a light system and was tested on this vehicle after Operation Sentry. Note the pair of vertically arranged headlamps in the center of the glacis.
Source: Pinterest

Lessons

Valuable experience with this new tank had been obtained in a relatively short time. A summary of the various faults, whether major or minor, was logged. From this and from discussion within the D.T.D., amendments to the A.41 design would be made.

The gearbox failures were perhaps surprising only in that they were so irregular and uncommon. A lot of previous problems during the war with tanks had been centered around gearbox trouble and yet this new transmission proved itself to have learned those lessons. The design had indeed taken knowledge from the Z51 Merritt-Brown unit which had been used in the Cromwell and Comet. The change was centered around adding a differential lock to the 7-speed (5 forward and 2 reverse) speed box, as this would help the driver to control one track over another in the event of becoming bogged down on soft ground.

On top of this change, a dry oil sump was fitted with oil injection for the gears, which helped both lubricate and cool the gears. A new double reduction system was part of the transmission and this was known as the Z51. The new gearbox was efficient and greatly improved the gear ratios in use to produce the power required at the sprockets. With the high-speed reverse gear added later to improve the design yet further, the nomenclature of the Z51-type box was now ‘Z51R’ (R for high-speed Reverse).

View into the engine compartment of the A.41, showing the Merritt-Brown Z51R transmission.
Source: Dunstan
A.41 Centurion P.11 (W.D. Index Number T.352417) during firing trials with the 17 pdr. Gun. Note that the turret rear has stowage boxes and the vague circle outline on the turret rear is now a hatch ideal for loading ammunition or for maintenance of the gun.
Source: Pinterest

The 7.92 mm BESA, venerable as its service had been, was requested to be replaced with the .30 caliber Browning machine gun. This was more reliable and another machine gun of the same type was requested for the commander on his cupola. All ideas of the somewhat impractical and wasteful use of a rear-facing BESA in the turret back were gone too.

The Polsten cannon idea had been to provide immediate firepower to destroy enemy anti-tank guns, where a machine gun was not powerful enough, and it was indeed a potent weapon in its own right. The real problem was that it simply took up too much space and a machine gun, like the BESA or the .30 caliber Browning, was simpler and allowed more space for the crew in the turret. Of the 6 tanks in Operation Sentry, only one had been fitted with the BESA and yet this was the preferred mounting – albeit replaced with the Browning.

The addition of the Morris 8 hp 3 kW auxiliary generator was a fine idea, as it would allow the tank to charge its radio batteries and gun control equipment even without the main engine turned on. However, it was felt that it would become unreliable over time and a new system would be needed. Nonetheless, the idea of having its own generator unit was novel and extremely valuable and would be kept.

“Generally, the CENTURION has been well received, and great interest is being taken in the trial”. AFV Technical Report No.26, June 1945

To improve off-road performance and to handle the slightly heavier weight of the vehicle, the prototype 20” (508 mm) wide tracks were changed to 24” (610 mm) when the A.41 entered production as the A.41*. Other modifications would include the hull stowage bin, but also the gun cradle, towing cable assemblies, and the final drive housings. Overall, these were minor amendments to the tank which had shown itself to be both fundamentally sound as a tank design, as well as being popular with the crews.

Like all good tests and trials, areas for improvement had been identified. There had been no opportunity for these tanks to see any actual combat or fire their guns in anger, but that was not the important thing. With a live test of the A.41 in a war zone and all of the difficulties which that entails in terms of the limitations on transport and supplies, the A.41 proved itself robust and reliable.

This perhaps was the single most important element which had often been found to be lacking on earlier British tanks. Produced under the extreme hardships of a wartime economy with limitations of materials and labor, and whilst often enduring German bombing, the nation’s economy had taken a serious beating. Yet, despite all of this, the British had managed to produce a tank to replace a fleet that still consisted of things like the A.24 Cromwell, A.30 Challenger, A.22 Churchills, and a plethora of M4 Shermans.

Trial End

With the trials over and the 6 Centurions returned to Great Britain via Calais in July, the results were discussed by the Director of the Royal Armoured Corps (D.R.A.C.) Advisory Committee meetings on 22nd August 1945. The theatre trials had been a resounding success and there was little hesitation in ordering 100 of the new tanks (very slightly modified) as A.41* of the initial batch of an order for 800 such tanks. The A.41, therefore was simply the prototype Centurion and it was the improved A.41* model which became the Centurion Mk.1. The remainder of the batch (700), was improved yet further as the A.41A and appeared as the Centurion Mk.2.

It was hard not to be impressed by the reliable and rugged Centurion. The Operation Sentry trials covered over 2,300 miles (3,701 km) for all six tanks with 250 miles (402 km) off-road and only minor problems were encountered. The new tanks were proudly shown off to other units within the 21st Army Group, following the long British Army tradition of a unit showing off their shiny new equipment to units that did not have it.

Centurion P.6 (T.352414) going over soft ground during trials in Operation Sentry, 1945.
Source: The Tank Museum.
One of the prototype A.41’s with 5th Royal Inniskilling Dragoon Guards, 1945. Note the port on the left of the turret, often referred to as a loading port but officially as a ‘revolver’ port, is open – likely for ventilation during this moment of relaxation.
Source: The Tank Museum, Bovington
A.41* Centurion Mk.I W.D. Index No. T.351701 – This is the second vehicle of that first batch of 100 A.41* tanks made by Royal Ordnance Factory Woolwich. Note that the 7.92 mm BESA has not yet been installed.
Source: Dunstan via IWM

The first 100 of those A.41A Centurions, later identified as Mk.2 tanks, would carry the same 17 pounder gun as before and then the rest (600 vehicles) were to carry a newer and even more powerful gun – the 20 pounder. The British had, by 1945, become masters of the gun, and this new 83.5 mm piece was a substantial step up in tank firepower beyond the 17 pounder. The big issue was that a new and larger gun beyond the 17 pdr., like the 32 pounder or this 20 pounder (originally a ‘21 pounder’ design), required a new fully cast turret to take it (the 95 mm Close Support (C.S.) gun version could be fitted to either turret).

Probably the biggest change from these P series vehicles to the first production vehicles would be the frontal armor. The 2.25” (57 mm) glacis was seen as being inadequate and this was increased to 3” (76 mm) for production vehicles, even though this thickness change is virtually imperceptible from the outside.

Production of the A.41 ‘Centurion’ would start in November 1945 from that August 1945 order, with serial production proper starting in 1946. Deliveries of that new tank started with the 6th Battalion Royal Tank Regiment in February 1946. This tank, the culmination of the British lessons of WW2, would go on to serve in dozens of armies over the following decades, and seeing combat all over the world. In the Centurion, and as proven by its trials on Operation Sentry, the British truly had produced one of the greatest tanks of all time, simple, rugged, reliable, and adaptable.

Survivors

Not many Mk.1 or even Mk. 2 Centurions survive today and even fewer of this first trials batch, just one in fact. Today, only P.9 survives as a pre-series Centurion. P.9 is preserved in The Tank Museum collection, Bovington, UK.

Centurion P.9., a Woolwich Arsenal-built tank, Index No. T352416, at The Tank Museum Bovington. Note that the driver’s windscreen is in the erect position.
Source: Flikr
A Centurion Mark I, similar to the ones that saw testing during Operation Sentry.

A.41 P-Series specifications

Dimensions (L-W-H) 25’ 2” long, 29’ 7” long over gun, 11’ 0.75” wide, 9’ 2.75” high
Total Weight 46.9 tonnes
Crew 4 (Driver, Commander, Gunner, Loader)
Gun Elevation Range +20 to -12 degrees
Speed 23 mph/h
Range 90 miles
Engine Rolls Royce Meteor Mk.4A petrol 635 bhp at 2,550 rpm
Radio No.38 AFV set, No.19 set, Infantry telephone
Fuel 120 gallons (545.5 liters)
Ground Clearance 20 inches
Trench Crossing 11´
Turret 360-degree rotation
Step 3’
Ford 4’ 9”
Armament 7 pdr., 7.92 mm BESA / 20 mm Polsten cannon, .303” Bren machine gun, 2” smoke bombs, multi-barrel smoke discharger
Armor Hull Glacis: 57 mm @ 55 deg., Nose: 57 mm @ 45 deg., Sides: 51 mm @ 12 deg., Rear: 38 mm @ 7 deg., Floor: 17 mm, Roof: 29 mm (hull front) 16 mm (centre), 14 mm (rear), Turret Mantlet: 127 mm, Turret Front: 127 mm, Turret Sides: 76 mm @ 10 deg., Turret Rear: 76 mm @ 10 deg., Turret Roof: 25 mm @ 78 deg. (front), 25 mm @ 90 deg. (centre), 25 mm @ 78 deg. (rear).
Total Production 6

Sources:

Report 38/TECH L1A/2/5, 21st Army Group British Liberation Army, AFV Technical Report No.26, June 1945
War Office Doc. 291. ‘Tank Data’
Dunstan, S. (2003). Centurion Universal Tank 1943 – 2003. Osprey New Vanguard. Osprey Publishing UK.
Dunstan, S. (2020). British Battle Tanks 1946-2016. Osprey Publishing, UK
Dunstan, S. (1980). Centurion. Ian Allen Publishing, UK
Ware, P. (2012). Images of War Special: The Centurion Tank. Pen and Sword Military, UK

2 replies on “Operation Sentry – The First Centurion Trials 1945”

There is or was a Centurion Mk.2 in an Egyptian museum. They were supplied with allegedly 28x Centurion Mk.3 but with only 5 or 10 APDS rounds per tank, which is why we never encountered them in the 1956 war. Why they have a Centurion Mk.2 in a museum is interesting if they were supposedly sent Mk.3…… The CIA OOB for 1966 for the Egyptian army incidentally lists them as Mk.2.

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