The Cromwell tank, officially Tank, Cruiser, Mk VIII, Cromwell (A27M),[a] was one of the series of cruiser tanks fielded by Britain in the Second World War. Named after the English Civil War leader Oliver Cromwell, the Cromwell was the first tank put into service by the British to combine high speed from a powerful and reliable engine (the Rolls-Royce Meteor), and reasonable armour. However, the originally proposed dual-purpose high velocity gun could not be fitted in the turret and the medium velocity dual purpose gun fitted proved inadequate. An improved version with a high velocity gun became the Comet tank.
The name "Cromwell" was initially applied to three different vehicles during development. Early Cromwell development led to the creation of the A24 Cavalier. Later Cromwell development led to the creation of the competing Tank, Cruiser, Mk VIII, Centaur (A27L) design. The Centaur tank was closely related to the Cromwell, both vehicles being externally of very similar appearance. Cromwell and Centaur differed in the engine used. While the Centaur had the 340 hp Liberty engine, the Cromwell had the significantly more powerful 600 hp Meteor.
The Cromwell first saw action in the Battle of Normandy in June 1944. The tank equipped the armoured reconnaissance regiments of the Royal Armoured Corps, in the 7th Armoured Division, 11th Armoured Division and the Guards Armoured Division. While the armoured regiments of the latter two divisions were equipped with M4 Shermans, the armoured regiments of the 7th Armoured Division were equipped with Cromwell tanks. The Centaurs were not used in combat except for those fitted with a 95mm howitzer, which were used in support of the Royal Marines during the amphibious invasion of Normandy.
|Tank, Cruiser, Mk VIII, Cromwell (A27M)|
Cromwell Mk IVd in the Kubinka Tank Museum
|Place of origin||United Kingdom|
|Used by||British Army, Israeli Army, Greek Army, Portuguese Army|
|Wars||World War II, 1948 Arab–Israeli War, Korean War|
|Designer||Leyland, then Birmingham Railway Carriage and Wagon Company from 1942|
|Manufacturer||Nuffield Mechanisation and Aero|
|Weight||27.6 long tons (28.0 t)|
|Length||20 ft 10 in (6.35 m)|
|Width||9 ft 6 1⁄2 in (2.908 m)|
|Height||8 ft 2 in (2.49 m)|
|Crew||5 (Commander, gunner, loader/radio operator, driver, front gunner)|
|Armour||3 inches (76 mm) on Mk.IV, 4 inches (100 mm) on Mk.V|
|Ordnance QF 75 mm|
with 64 rounds
|2 x 7.92 mm Besa machine gun|
with 4,950 rounds
|Engine||Rolls-Royce Meteor V12 petrol|
600 hp (450 kW)
|Power/weight||21.4 hp (16 kW) / tonne|
|Transmission||Merritt-Brown Z.5 gearbox (five forward and one reverse gear) driving rear sprockets|
|Ground clearance||16 inches (410 mm)|
|Fuel capacity||110 imp gal (500 l) + optional 30 imp gal (140 l) auxiliary|
|170 miles (270 km) on roads, 80 mi (130 km) cross country|
|Speed||40 mph (64 km/h) with 3.7:1 final reduction drive|
Development of the Cromwell and Centaur dates to 1940, as the Crusader tank was being readied for service. The General Staff was aware that the Crusader would become obsolete, and in late 1940 they set out the specifications for a replacement tank, expected to enter service in 1942, fitted with the QF 6 pounder gun.
Vauxhall responded with the A23, a scaled down version of their A22 Churchill infantry tank. This would have had 75 mm of frontal armour, used a 12-cylinder Bedford engine, carried a crew of five and would have had the same suspension as the A22.
Nuffield submitted the A24, heavily based on its Crusader design and powered by its version of the Liberty engine, a V-12 design dating the late days of World War I and now thoroughly outdated. Nevertheless, as the design was based on the Crusader, it was expected it could be put into production rapidly.
The designs were received and examined in January 1941, with Nuffield's A24 being declared the winner on 17 January. Six prototypes of the Cromwell were ordered for the spring of 1942. These arrived four months late, and by this time the design was already outdated. It was put into production anyway, but in service it proved underpowered. Only a small number were built.
With the start of the war, Rolls-Royce ended car production and set up a design team looking for other ways to use their design capability. The team formed under the direction of Roy Robotham at Clan Foundry near Belper, north of Derby. They began recovering and refurbishing parts from crashed Merlin engines with the intention of using them for non-aviation purposes.
In October 1940, Robotham met Henry Spurrier of Leyland Motors to discuss British tank design. The Tank Board desperately needed a more powerful tank engine to replace the aging Liberty. Robotham and Spurrier decided to attempt to fit a refurbished and re-worked Rolls-Royce Merlin engine to a Leyland tank for testing. Design had three priorities:
They removed the supercharger from a Merlin Mk. III to downgrade the performance to a suitable level for tank use, reversed the direction of engine rotation to match tank transmissions, and fitted the resulting engine to a Leyland-built Crusader.
Delivered to Aldershot on 6 April 1941, the test team had trouble timing its runs because it was so fast, estimating it reached 50 miles per hour (80 km/h). Leyland arranged to start production of 1,000 examples of the engine as the Meteor.
With engine power doubled, it soon became apparent that the additional stresses placed on the Crusader components required significant re-work to increase reliability. Leyland had no spare capacity, and re-work commenced with the help of BRC&W. It was planned to fit this to BRC&W-built versions of their original A24 submission.
Refitting the design of the A24 Cromwell for the Meteor engine was not acceptable to Nuffield, and hence a new specification of tank was created working with Leyland, the A27 Cromwell.
In mid-1941, Leyland changed its mind, concerned about cooling problems. This was a major concern for the Tank Board, as cooling issues had been a major problem for the previous generation of Crusader and Covenanter tanks. The Tank board was still committed to the Meteor, but to avoid dedicating all resources into a potentially flawed design, the design was split into three separate vehicles:
These early design designations of Cromwell I, II, and III are not to be confused with the later production designations of Cromwell I, II, etc. which were production variants of the A27M.
While Leyland continued with the Liberty under A27L, the Tank Board continued with the Meteor engine by placing an order directly with Rolls-Royce. Leyland also suggested using a diesel engine of their own design, although this was later abandoned.
Cromwell's cooling system was a new design and put through over nine months of testing in a variety of configurations. This included the development of new fan drives and inlet louvers, which can be seen on the Cromwell engine deck. The resulting system for a Meteor-powered tank delivered both the necessary cooling performance, and reduced the power lost in driving the cooling system from 90 hp to 30 hp. This made the performance improvement of the Meteor over the Liberty even more pronounced and left room for expected development of the A27.
The first (mild steel) prototype of a Meteor-powered A27M Cromwell was delivered to the Army for trials in March 1942, several months before the A24 that was supposed to precede it, and also prior to the A27L Centaur pilot vehicle. With nearly 600 hp (450 kW) it proved to be exceptionally mobile when tested.
Orders were placed for both A27L and A27M versions as there were concerns about the production rate of the Meteor. Design also commenced on a 17-pounder armed version under specification A30, leading to parallel development of the A30 Challenger.
As all of Rolls Royce's production capacity was engaged in producing the Merlin engine for aircraft, production of the Meteor versin was initially based solely on parts recovered from crashed aircraft, with many engines still showing crash damage. Additional sources for manufacturing the Meteor engine were investigated. Even when assigned reduced production quotas, BRC&W proved unable to meet the demand for Cromwell, and Leyland became the design and production parent of both the A27L and A27M versions including subcontracted work.
Rolls was at this time having trouble meeting demand for the Merlin, let alone the Meteor. Meanwhile, Rover was having troubles developing Frank Whittle's Power Jets W.2 jet engine design due to increasing animosity between the engineers at Power Jets and Rover. Things became particularly heated when Whittle learned that Rover had set up a secret lab to develop their own versions of the design. Whittle had, during the same period, contacted Rolls for help delivering some of the required parts that Rover proved unable to produce.
A solution to both their problems was offered by Ernest Hives, a Rolls board member, who had met Whittle and was fascinated by the jet engine. Hives called a meeting with his counterpart at Rover, Spencer Wilks, and the two met late in 1942 at the Swan and Royal pub in Clitheroe. Hives offered to trade the Meteor for the W.2, an offer Wilks jumped at. Rover set up production at their Tyseley factory, and an additional line was set up by Morris Motors in Coventry.
Production began in November 1942. That month, new names were given to all three designs; the original A24 Cromwell I became the Cavalier, the Liberty powered A27L Cromwell II became Centaur, and the Meteor powered A27M kept the name Cromwell. It would take considerable time for Rover to make ready production lines for the Meteor, and it was not until a few months later, in January 1943, that sufficient Meteor engines were available and the A27M Cromwell began production. The official handover of the Meteor and W.2 took place on 1 January 1943.
Ramp-up of Meteor engine production with Rover and Morris was heavily dependent upon machine tools from the US. This took time to achieve. In the interim, Centaur production continued to avoid closing Cromwell tank production lines.
Cromwell had originally been intended to mount the high velocity QF 6-pounder tank gun as primary armour piercing (AP) armament with a few mounting the Ordnance QF 95 mm howitzer to fire high explosive and smoke shells for close support role.
The earlier introduction of US M3 Grant and M4 Sherman tanks placed a dual purpose 75mm gun into British and Commonwealth service. The 75mm could fire a more effective HE shell compared to the 6pdr at the cost of a reduction in armour-piercing performance. The 6-pounder firing solely AP shells was a backward move in overall capability. Once the Vickers 75mm HV gun was seen to be too big for the Cromwell turret, work was begun in December 1942 on the Ordnance QF 75 mm (a development of the 6pdr that fired US ammunition) for fitting to British tanks. Mark IV Cromwells were delivered with 75mm from November 1943.[c]
To maintain the capability to take on Axis tanks, production was to be split:
Noting the issues with the medium velocity 75mm dual purpose weapon, Vickers had already commenced development of a high velocity 75mm that would fire American 75mm ammunition but at a much higher velocity.
While Cromwell development had been underway, Soviet forces rejected the US Sherman tank that was to be provided through the third protocol of lend-lease. This led to a surplus in Sherman tank manufacturing capacity, and significant pressure was placed for the Cromwell programme to be cancelled in favour of US produced Shermans. This would otherwise see a significant proportion of Sherman tank assembly lines closing.
A complete move to Sherman tanks was not acceptable to British forces who would then be completely dependent on the US for tank production. At the same time, Cromwell with the Meteor engine and a HV weapon was shown to have superior power and armament, while US efforts to produce the Sherman's replacement, the T20 Medium Tank, were not receiving sufficient attention. The impact of ceasing tank manufacture in Britain would keenly be felt by workers and the war economy at home.
A compromise was achieved with a reduction in British tank production during 1943 and 1944, with an increase in consumption of Sherman tanks, the remainder being delivered in parts as spares. Centaur production bore the brunt of this reduction, having only been continued to maintain factories producing Cromwell hulls while the number of Meteor engines were short. It had already been arranged that Centaur production would be phased out when Meteor engine production ramped up. The list of machine tools required for a ramp-up in Meteor production was also agreed, allowing Cromwell manufacture to scale.
At the same time as negotiations with the US, problems were being encountered with the use of the Vickers 75mm HV gun onto Cromwell, with a larger turret ring being required. This was now expected to be introduced in mid 1944, leaving the majority of current Cromwells with the medium velocity gun similar to Sherman. Design of the high velocity variant was split to a separate specification. Intended as just another version of Cromwell, the new A34 version eventually needed significant re-engineering leading to production of the A34 Comet, which used a high velocity gun firing 17pdr ammunition from a smaller gun. In the interim, the A27M version started to ramp-up production.
The first real field test of the design was carried out in August–September 1943, when examples of the Centaur, Cromwell, Sherman M4A2 (diesel engine) and Sherman M4A4 (multi-bank petrol engine) were all tested in Exercise Dracula, a 2,000 mile long trip around Britain. The Shermans proved to be the most reliable, by far, requiring 420 hours of specialist fitter attention over a total distance travelled of 13,986 miles (22,508 km). This corresponds to 0.03 hours per mile. In comparison, the Cromwells drove 11,582 miles (18,639 km) and required 814 hours, or 0.07 hours per mile. The Centaur managed only 8,492 miles (13,667 km) due to constant breakdown, and required 742 hours, or 0.087 hours per mile.
The Cromwell and Centaur were given additional time to work out these problems. The Cromwell's problems were mostly related to oil leaks and brake and clutch failures, an observer noting that these were well-known and should already have been corrected. The crews, however, expressed their love for the design, and especially its speed and handling. The Centaur was largely dismissed, with one observer expressing his hope that units were being equipped with it only for training purposes. The same reviewers unanimously supported the Sherman. A similar test in November demonstrated the Cromwell was improving, while the underpowered Centaur fared no better than the first test.
Alongside Cromwell production, Centaur production design also allowed for the later conversion to the Meteor engine. A small number were retro-fitted for trials as Cromwell III and Cromwell X. As the Cromwell proved itself, larger numbers were fitted with the Meteor engine on the production line as Cromwell III and IV (not to be confused with the earlier Cromwell III design project).
The production model design was finalised on 2 February 1944 when Leyland released specifications for what they called the "Battle Cromwell".
This included a number of minor changes to the basic design, including 6 mm (0.24 in) of extra armour below the crew compartment, the introduction of an all-round vision cupola for the commander, seam welding all joints to waterproof and strengthen the tank, and standardizing on the A27M version with Meteor engine and Merritt-Brown transmission.
The Cromwell Final Specification was applied part way through the production of Cromwell III and IV, changing the appearance and specification of both vehicles. The specification was later improved toward the end of the war with the Cromwell VII, resulting in an upgrade programme.
Centaur and Cavalier never met the requirements to enter front-line service. Most were used for training, although a few notable exceptions were used in action.
Total A27 production consisted of 4,016 tanks, 950 of which were Centaurs and 3,066 Cromwells. In addition, 375 Centaur hulls were built to be fitted with an anti-aircraft gun turret; only 95 of these were completed.
Production was led by Leyland Motors on Centaur, and Birmingham Railway Carriage and Wagon Company on Cromwell. Several other British firms also built Centaur and Cromwell tanks, however, as the numbers required were greater than any one company could deliver. Companies contracted to build the tanks included English Electric, Harland and Wolff, John Fowler & Co., LMS Railway, Metro-Cammell, Morris Motors and Ruston-Bucyrus.
Production of Cromwell and Centaur was split into two different groups. Cromwell was to be built by BRC&W and Metro-Cammell while Centaur was to be built by Leyland, English-Electric, Harland & Wolf, John Fowler & Co., LMS, Morris, Ruston-Bucyrus. Nuffield also switched production to Centaur when Cavalier completed. To increase Cromwell production capacity, English Electric switched from manufacturing Centaur to Cromwell, but remained tooled for Centaur. This resulted in a number of Cromwells being built with Centaur hulls. By January 1943, when production started, Leyland had become the production and design lead for A27 series including subcontractors producing components. Records show that John Fowler & Co. also produced both varieties.
Vauxhall produced two Cromwell pilot models - with a turret similar to that of the Churchill - in the expectation that they would build Cromwells once production of Churchill was terminated in 1943 but Churchill production was extended and Vauxhall withdrew from Cromwell programme.
The frame was of riveted construction, though welding was used later. The armour plate was then bolted to the frame; large bosses on the outside of the plate were used on the turret.
The suspension was of the Christie type, with long helical springs (in tension) angled back to keep the hull sides low. Of the five road wheels each side, four had shock absorbers. The tracks were driven by sprocketed wheels at the rear and tension adjusted at the front idler, this being standard British practice. Some variants were produced with 14-inch-wide (360 mm) tracks; later, 15.5-inch tracks were used. As with previous Christie-suspension cruiser tanks, there were no track return rollers, the track being supported instead on the tops of the road wheels, known as the "slack-track" design. The side of the hull was made up of two spaced plates, the suspension units between them, and the outer plate having cutouts for the movement of the road-wheel axles.
The gearbox had five forward and one reverse gears. The first gear was for "confined spaces, on steep inclines or...sharp turns". The transmission was the new Merrit-Brown Z.5, which offered differential steering without clutching or braking, a major advance on previous designs. It gave the Cromwell superb maneuverability, with only the German Tiger I, using a similar design, able to match it.
The Meteor engine delivered 540 hp at 2,250 rpm giving the Cromwell speed as well as maneuverability. This was the maximum rpm, which was limited by governors built into the magnetos. Fuel consumption on "pool" petrol (67 octane) was between 0.5 and 1.5 miles per gallon depending on terrain.
The driver sat on the right in the front of the hull, with the hull gunner on the left, separated by a bulkhead. The driver had two periscopes and a visor in the hull front. The visor could be opened fully or a small "gate" in it opened; in the latter case, a thick glass block protected the driver. A bulkhead with access holes separated the driver and hull gunner from the fighting compartment.
A further bulkhead separated the fighting compartment from the engine and transmission bay. The engine compartment drew cooling air in through the top of each side and the roof and exhausted it to the rear. To allow fording through up to 4 ft (1.2 m) deep water, a flap could be moved to cover the lowermost air outlet. Air for the engine could be drawn from the fighting compartment or the exterior; it was then passed through oil bath cleaners. It was modified so that the exhaust fumes were redirected so that they were not drawn into the fighting compartment, a problem found when tanks were drawn up together, preparing to advance.
In June 1944, the Cromwell saw action during Operation Overlord, the Allied invasion of Normandy. It had a mixed reception by crews, being faster, with a lower profile and thicker frontal armour plate than the Sherman tank, but also being smaller and more cramped. Cromwell had 3 in (76 mm) of frontal armour compared with 2 in (51 mm) on the glacis of the early Shermans, though it was unsloped and hence less effective in head-on combat On later Cromwells this was further increased, first to 3 1⁄4 in (83 mm), then to 4 in (100 mm).
In common with British tank doctrine of the time, the vehicle was designed to fire on the move. The turret offered hydraulically powered turret traverse motors with proportional speed control. Later vehicles fitted an all-round view cupola for the commander to identify and track targets. Both gunner and commander had Vickers rotating and pivoting periscopes, while episcopes were fitted in the cupola. There was a 7.92 mm Besa machine gun mounted co-axially to the main armament, operated by the gunner. A second was gimbal mounted in the front of the hull, with 45 degrees horizontal and 25 degrees vertical movement. Sighting was by a No. 35 telescope, which was connected through a linkage to the mounting. In the top of the turret was a 2-inch "bombthrower" angled to fire forward. Thirty smoke grenades were carried for it.
Early models of the Cromwell were equipped with the QF 6-pounder (57 mm). Using the new Armour-piercing discarding sabot round, which became available in quantity in early 1944, this gun could penetrate over 100 mm of steel armour at ranges on the order of 1,000 yards (910 m), making it effective against all but the most heavily armoured tanks. However, British tankers had long complained about this weapon's lack of a useful high explosive (HE) round for attacking soft targets like trucks, anti-tank guns and infantry defences. A HE shell had been introduced for the 6-pounder, but it was described as being largely useless - the calibre of the gun was simply too small to carry a useful load of explosive. This was not entirely accidental; British tank policy of the time suggested that different models of the same tank, carrying different specialized weapons, was a better solution to this problem than a single weapon that attempted to do all things.
Experience with the US M3 75 mm gun suggested this thinking was wrong, that a single gun could be used in a "dual purpose" role against both tanks and softer targets. This led Vickers to begin development of a 75 mm weapon of 50 calibres in length, which would fire the same HE shell as the US gun, but with a higher propellant load that would make its anti-tank rounds more effective. However, as examples of this weapon began to arrive in May 1943, it was clear it would not fit into any turret that could be mated to the Cromwell's turret ring.
This problem was eventually solved by the realization that the 6-pounder could be bored out to 75 mm and fire unmodified US ammunition. While this would lead to less anti-tank performance, this was considered a reasonable trade-off in exchange for the rapid introduction of the HE rounds. The resulting ROQF 75 mm could be easily swapped out with the 6-pounder, and newly built models mounting the gun were known as the Mark V. The ROQF 75 mm would be the primary weapon for the majority of Cromwells produced.
A close support version of the Cromwell was fitted with the 95 mm howitzer in place of the 75 mm. This too fired HE, though its primary role was delivering smoke shells, covering the other tanks in the unit.
Some command or OP tanks had the armament removed, leaving space in the turret for further radios. These were fitted with a dummy wooden gun, so as not to appear different to the enemy and attract hostile fire.
Aside from the engine and its ancillaries (fans, radiator, clutch, etc.), both vehicles are very similar designs. While similar however, there were a number of minor variations between Cromwell and Centaur caused by the divergence of design and production.
Increases in Cromwell's design weight from 24 to 27 tons resulted in a reworking of the suspension during the design process, which was not reflected on Centaur. Cromwell had heavier grade suspension with longer suspension arms. Cromwell's shock absorbers and springs were improved against Cavalier, and increased to four (compared with Centaur's three).
The method of track tensioning is a commonly noted difference. Initially, the design based on A24 Cavalier used a worm drive for tensioning. This was noted as being slow to operate, and trapped dirt. BRC&W developed an alternative ratchet mechanism based on the Valentine tank, and this was incorporated into the A27M Cromwell design, also enabling the tank to accept wider 15.5" tracks. Centaur under Leyland continued without this development.
Some of these differences can be seen in Cromwells built with Centaur hulls, although many were removed with the introduction of the Cromwell Final Specification. This included the Cromwell method of track tensioning.
By comparison, Cavalier can easily be identified by the vehicle's rear armour plate, which incorporates Crusader style horizontal angled exhaust louvres. Cromwell and Centaur both have a flat rear armour plate, with exhaust venting to the top immediately behind the engine deck. For this reason, many Cromwell and Centaur vehicles had a cowl fitted to direct the exhaust gases back where they could not re-enter the tank fighting compartment.
An earlier requirement for a 17-pounder armed tank became more important when the Vickers HV 50 calibre 75mm gun failed to fit on Cromwell. A version of Cromwell mounting the more powerful Ordnance QF 17-pounder (76.2 mm) had been commenced early in the development process. This required a much larger turret ring, which in turn required the hull to be lengthened and an additional road wheel to be added to each side for a total of six. The result was the Cruiser Mk VIII Challenger, but these were somewhat unwieldy and produced only in small numbers. While successful, production ceased with the much easier conversion of Sherman Firefly allowing greater numbers to be fielded.
However, development of the Vickers HV 50 calibre 75mm gun continued, with the bore increasing to fire modified versions of the 17-pounder ammunition. This gun and its ammunition were designed specifically to fit in a turret that a reworked Cromwell-sized design could carry. This became the 77 mm HV with only slightly lower performance than the base 17-pounder. By the time this weapon was ready, a number of other changes had been worked into the tank design, producing the Comet, which replaced both the Cromwell and Challenger.
The A24 design specification had originally been constrained by the available tank engines of the time, delivering only 300 hp and limiting the weight. The evolution to A27M increased the weight slightly, but fitting a 600 hp engine almost doubled the power-to-weight ratio and created a very fast tank. This was combined with the Merrit-Brown gearbox that allowed the tank to steer while still powering both tracks, allowing it to maintain speed while maneuvering, while tanks like the Sherman or T-34 lost power while turning and necessarily slowed down.
Cromwell was the fastest British tank to serve in the Second World War, with a top speed of 40 mph (64 km/h). This speed was extremely beneficial in both attack and defence, outmanoeuvring opponents. At least one case is known of vehicle commanders using the vehicle's fast speed to jump large gaps. In The Netherlands, a troop of three Cromwells was able to leap a 20 ft wide canal when surprised by enemy forces
This speed proved too much for even the Christie suspension and in later models the final drive ratio was changed to lower the top speed to 32 mph (51 km/h), which was still fast for its time. Thanks to its excellent engine power and Christie parentage, the Cromwell was very agile on the battlefield.
The Cromwell's armament was changed from the 6-pounder to the dual purpose 75mm. This gave a significant reduction in armour penetration compared to newer 6-pounder ammunition, which was becoming available, but added the ability to fire High Explosive shells, which were more capable against other targets, such as anti-tank guns. The High Velocity 75mm gun was developed in an attempt to give both good anti-tank and HE performance, but in May 1943 proved too big to be fitted to the Cromwell. This issue led to the development of the A34 Comet, while the gun bore was increased to 76.2mm to gain compatibility with the 17-pounder (albeit with smaller shell casings). The lack of a High Velocity weapon proved to be a significant limitation against opponents such as the Tiger, and Cromwell had to rely on mobility.
The dual purpose 75 mm main gun fired the same ammunition as the US 75 mm gun as used on the Sherman, and was also fitted to the Churchill, it had around the same HE and armour-piercing capabilities as the 75 mm equipped Sherman tank. The Cromwell's speed and low profile gave an advantage over the Sherman however, giving the tank the element of surprise and making return fire more difficult. Cromwell crews in North-West Europe succeeded in outflanking the heavier and more sluggish German tanks with superior speed, maneuverability and reliability.
The armour on the Cromwell ranged from 8 mm up to 76 mm thick overall. On all-welded vehicles built by BRC&W, the weight saved by the welding allowed for the fitting of additional appliqué armour plates on the nose, vertical driver's plate and turret front, increasing the maximum thickness there to 102 mm. These vehicles are identified by their War Department numbers carrying the suffix W, e.g. T121710W. The armour compared well with that of the Sherman, although the Cromwell did not share the Sherman's sloped glacis plate.
While the Cromwell was a match for the majority of Axis tanks in use, it was not a match for the armour and armament of the latest German vehicles developed at the same time. British tank design would go through another stage, the Comet, before developing the Centurion tank.
The Cromwell tank entered front-line service with the Allied invasion of Normandy in June 1944. Cromwells landed with the following forces on D+1. They saw extensive action with the British Army, forming part of the 6th Airborne Division, 7th Armoured Division, 11th Armoured Division, Guards Armoured Division, and 1st (Polish) Armoured Division. The tank was also used by the 1st (Czechoslovakian) Independent Armoured Brigade Group as part of the First Canadian Army in Dunkirk.
Cromwells were used as the main tank in the armoured brigades of the 7th Armoured Division, while being used in the armoured reconnaissance regiments of the other British armoured divisions (Guards Armoured Division and 11th Armoured Division) in North-west Europe. It excelled at this task because of its speed and low profile. The tank was praised for its speed and reliability, while its low profile made it harder to spot.
The standard 75mm gun could tackle the majority of German armoured vehicles, and the HE shell was effective, but could not penetrate the front of heavier German tanks such as the Tiger or Panther. Although a rare occurrence on the battlefield, during the Battle of Normandy it was in the British sector where the majority of these German machines were encountered. The issue with the 75mm gun was perhaps most pronounced during the Battle of Villers-Bocage in which the Cromwells were unable to engage German Tiger tanks frontally with any reasonable chance of success. It should be noted however that several Tigers were knocked out by British forces in the battle nonetheless.
The 75mm HV had been intended to rectify this, but prior to entering service it was found to be too large to fit in the Cromwell turret. Instead Cromwells fought alongside the 17pdr armed Sherman Firefly or Challenger, both of which could destroy Panthers and Tigers at standard combat distances. Cromwells (and 75mm armed Shermans) were supplemented by these vehicles at varying ratios per troop of 1/2 to 1/3. Though this provided a good solution to the issue of heavy German tanks, it added an additional level of complexity for battlefield commanders in having to place the 17pdr armed vehicles tactically within a formation. However this complication was not unique to the British army, the US employed similar methods and faced the same issue with their arsenal of 75mm armed Sherman tanks.
This situation persisted until the development of the A34 Comet was concluded, mounting the new 77mm HV gun and removing the need for mixed units. 
In contrast, the Centaur was chiefly used for training; only those in specialist roles saw action. The Centaur IV Close Support version with a 95 mm howitzer saw service in small numbers as part of the Royal Marine Armoured Support Group on D-Day. Originally intended to serve as static pillboxes, these examples retained the engine allowing the Marines to advance the tank inland. A number of Centaurs were also re-purposed as combat engineering vehicles, such as an armoured bulldozer.
The Sherman remained the most common tank in British and other Commonwealth armoured units in Europe. The Cromwell, in turn, was succeeded by small numbers of the Comet tank. This was based on the Cromwell and shared many components but had been designed from the outset to mount a superior gun, the 77 mm tank gun (a version of the 17 pounder with different ammunition). Only the 11th Armoured Division was fully re-equipped with the Comet before the war ended.
Cromwell Tanks were used by Czechoslovakia, Israel and Greece.
Fifty-two Centaur I tanks were donated in early 1946 to the Greek Army, during the opening stages of the Greek Civil War but they were kept in storage due to the lack of trained personnel. In 1947, the first Greek officers returned from training courses in the United Kingdom and training of tank crews began. In April 1948, the Centaurs were organized in three Centaur tank companies initially numbered II, IX and XI, but a year later were renumbered 381, 382, 383 and temporarily attached to Reconnaissance Regiments 391, 392, and 393. The Centaurs saw limited service in the war because battles were fought mainly on mountainous areas, but proved useful in supporting infantry units and in defense of inhabited areas. After the end of the war, in October 1949, the three Centaur companies were organized into the 391 Tank Regiment. The Centaurs were replaced by US built M47s and in 1962 were sold and scrapped. One Centaur is preserved in the Greek Army Tank Museum.
A number of countries also used the upgraded Charioteer version of the Cromwell post war. These saw action in conflicts in the Middle-East.
Development of hull types and armaments occurred independently. Hull types applied to all variants. A single mark could cover up to four types, and a type up to six marks making classification complex. Combinations of mark and type were applied by different manufacturers.
Hull types ranged from Type A to Type F. Each type applied a different package of changes to the hull design to different marks of tank. Changing the vehicle type allowed the introduction of changes without changing the overall offensive capability.
|Cromwell type||Construction||Major features||Cromwell Mark|
|A||Riveted||First version with:
|B||Riveted||As A, but:
|C||Riveted||As B, but:
Later vehicles added:
|As C, but:
On welded vehicles:
|As D, but:
On welded vehicles:
|F||Riveted||As E, but:
Later vehicles added:
A number of further vehicles were based on the Cromwell tank hull, either re-working existing vehicles or built from scratch with the Cromwell as the basis:
Post-war, a number of Cromwells were upgraded to meet the new Cold War threat:
The Cromwell tank design was also used as the basis for the design of following vehicles:
The majority of following British tank designs utilised the Meteor engine and Merritt-Brown steering & gearbox combination initially developed for the Cromwell, lasting all the way through Centurion. This proved to be one of the primary elements in the development of the Main Battle Tank.
Around 56 Centaur and Cromwell tanks survive, ranging from scrapyard wrecks to fully restored museum vehicles.
Around 26 Cromwell tanks exist in various states.
Around 17 Centaurs and 9 Centaur Dozers exist in various states.
Other examples include: