Friday, 4 March 2016

Cromwell: English Dictator in Soviet Fields

Over the years of the Great Patriotic War, over 5000 British and Canadian tanks were sent to the Soviet Union. Most of them were so called Infantry tanks, with thick armour and low speeds. Light tank shipments were limited to 20 Tetrarchs. As for Cruiser tanks, they never made it into the Red Army. Despite an initial desire to receive Cromwells, they only made it to the trial stage. Read on to discover why these tanks were rejected.

Intelligence Reports

The first proposal to send Cruiser tanks to the USSR was made in the spring of 1942. The British offered as a supplement to Matildas, Valentines, and Churchills: Cruiser Tank Mk.VI, or, since spring of 1941, Crusader. This successor to the Cruiser Tank Mk.III entered production towards the end of 1940. This was a completely new tank, and a much more successful one than its predecessor. At the same time, it retained some of their drawbacks, like weak armour and not exceptionally reliable Nuffield-Liberty engine.

GABTU made a request for information from appropriate organizations. In addition to official channels, foreign intelligence was activated, and obtained exact information on the production volume and the factories that make the tanks. At first, the tank was rejected due to its gasoline engine. Other tanks shipped to the USSR had diesel engines. In addition to this, information regarding the German evaluation of the Crusader in North Africa was obtained. The Germans considered the tank quick, but lightly armoured.

Cromwell IV, registration number T.187888, Kubinka Proving Grounds, September 1944

Meanwhile, the War Office has been thinking about a replacement for the Crusader since 1940, the same year it entered production. Requirements were given to three companies: Vauxhall, Nuffield, and Birmingham Railway Carriage & Wagon Company (BRC&W). The best result came from Nuffield, the A24. The Crusader served as the foundation for this 27 ton vehicle. The tank was adopted under the index Cruiser Tank Mk.VII or Cavalier, but the tank's fate was sealed from the very beginning. The fault of this was the same Nuffield-Liberty engine. This drawback opened up a path to the Crusader III, armed with a 6-pounder (57 mm) gun.

The problematic vehicle was not discarded, and it was decided to keep working on it. The result was two more tanks, both with the index A27, but with an extra letter. The A27L was the Centaur tank, produced by Leyland and equipped with the Nuffield-Liberty engine. The A27M was the Cromwell tank, produced by BRC&W and equipped with a Meteor, a reduced power version of the Merlin aircraft engine. The new engine was not only more reliable, but one third more powerful.

Soviet specialists encountered this new tank in 1942. On November 13th, a  member of the trade representative commission in Great Britain, K. Olkovskiy, visited the Chobham proving grounds. Here he saw two experimental Cromwell I tanks without armament.

These tanks showed smooth driving on cross-country terrain. However, they were plagued by minor defects in the gearbox, and after 5 km off-road, the water in the radiator started boiling. Suspension springs broke several times. At Olkhovskiy's request, he was given the specifications for this vehicle. He did not believe the specified mass of 27 tons, and left with a general impression that the demonstration was staged to show that the vehicle was not ready. In his opinion, the British did not want to send this tank as a replacement for Matildas or Churchills. In reality, the tank was simply not ready. It took another year to perfect it.

The tank is covered in directions for shipping. A sign covering the whole rear instructs workers to not transport the tank on the upper deck.

In March of 1943, GRU agents learned about the mass production of Cromwell, Centaur, and Cavalier tanks. A report was composed that made its way to GBTU through director of the 3rd GRU Directorate, Major-General V.E. Khlopov. According to this report, by March of 1943 8-10 thousand Cromwells have been built, and 45 units were built each day by 15 tank factories. This information also came from Olkhovskiy. 

Based on this new information, Khlopov suggested that new tanks should be bought instead of Matildas. On April 3rd, the chief of GBTU, Colonel-General Fedorenko, sent a proposal to Molotov to purchase Cromwell tanks instead of Matildas. The trade representatives and GRU agents in Britain were instructed to find more information about these new tanks. It was quickly discovered that the Centaur used the Nuffield-Liberty engine, and interest in that tank waned. There was, however, a proposal to ship the Centaur, judging by a letter from the British War Mission in the USSR.

Same tank, viewed from the front.

According to the document, the British were ready to send Centaurs, but instead, the War Office proposed sending more Shermans. These were British equipped M4A2s (with British radios and some changes in equipment), indexed Sherman III in the British Army. Effectively, the British were offering to resell tanks that were shipped to them by the Americans.

According to the correspondence, that was the end result. Even though the British were happy to show the Centaur to Soviet representatives in Britain, the whole affair petered out, since GBTU was more interested in Shermans, even if they were British variants.

Better Late than Never

The next time anyone thought of Cromwells was in the spring of 1944. In a letter sent on March 17th, Deputy People's Commissar of External Trade, I.F. Semichastnov, asked Fedorenko's opinion about purchasing these vehicles. The letter highlighted the fact that the Cromwell was the best tank produced in Great Britain. By then, supplies of British vehicles ended.

This time, things went further than just letters. GBTU ordered six tanks, some of which were used for mobility trials, some of which were shot up to test their armour, and at least two were sent to various institutions for disassembly and study. For various reasons, the six tanks arrived in Baku only on August 18th, 1944. According to documents, they should have been loaded on trains on August 24th, but there was a 5 day delay.

The Cromwell's engine and transmission compartment.

Let's stop for a second to look at what vehicles exactly were shipped to the USSR. Many flame wars were fought over which modification of the tank was sent. Claims that these were Cromwell VIIs are incorrect. The vehicles were Cromwell IVs, the most numerous variant. These tanks were built in May of 1944, so the USSR was getting brand new vehicles. The only strange part is that their hull modification is specified as E in the documents. The engine compartment roof is indeed of the E type, but the assistant driver's hatch is consistent with B and C type hulls.

By the time the Cromwells arrived in the USSR, tanks of this type have already been fighting in Normandy for two months. Only the 7th Armoured Division had Cromwells as its main fighting force. In the 11th and Guards tank divisions, Cromwells composed about a third of the park, while the rest was made up of the British Sherman "workhorse", the M4A4. The 1st Polish Armoured Division also had a similar ratio of tanks. The Czechoslovak Tank Brigade also had some Cromwells. This unit was almost entirely composed of British vehicles.

In general, British tankers were sceptical towards Cromwells, preferring the Sherman. American tanks were more reliable, more fuel efficient, and had a better designed turret and hull.

Dirt road mobility trials.

Soviet intelligence did not know about these opinions, but some information leaked through. According to this information, the exhaust system was poorly designed, and rising fumes betrayed the vehicle's location, especially in moist weather. Special tin screens were designed quickly, but they limited the gun's depression when firing backwards and their lifespan was very short.

The mudguards were also poorly designed, as they constantly bent and were torn off on dirt roads. The remaining shiny metal also revealed the vehicle. The driver's emergency exit hatch also earned some complaints. The gun mantlet was deemed poor, as there was an instance where the mantlet was penetrated through the BESA mount, leading to the death of the loader.

A Year Too Late

The Cromwell IVs arrived at Kubinka in early September of 1944. Brief trials of vehicle number T.187888 began on September 8th. The trials lasted until September 11th. Their goal was to verify the tactical-technical characteristics of the tank. Information regarding the penetration of the 75 mm Mk.V gun on the Cromwell was also obtained.

Cromwell IV on an incline.

The gun on the Cromwell IV was a result of British and American cooperation. It was based on the 6-pounder gun, but the caliber and ammunition used were American. Its penetration was less than that of the long-barrelled 57 mm gun, but only slightly, and it solved the issue with a lack of HE rounds. This gun was well received by the army, and some existing Cromwells and Churchills were re-armed with it.

As a result of trials, the aimed rate of fire of the tank was about 9 RPM from standstill and 7 RPM at a speed of 9-12 kph. The target for the Cromwell was a Tiger E. At 500 and 600 meters, the M61 shell penetrated the side of the turret completely. At 650 meters, the shell made a 75 mm deep dent and two cracks. To compare, the 75 mm American gun on the M4 Sherman could penetrate this armour at 640 meters, and the 76 mm F-34 couldn't penetrate it with a stock shell at 100 meters.

While driving across swampy terrain, the Cromwell did not get stuck, but it did not behave as confidently as an M4A2 Sherman or a T-34.

The visibility of the crew was good, due to a large amount of Mk.IV periscopes. The commander's working conditions were deemed adequate. The gunner's workspace was given a much higher grade, due to his ability to easily aim and traverse the gun simultaneously. The gunner also had access to a hydraulic turning mechanism.

The loader's conditions were much worse. Only the ready rack on the turret basket was easy to work with. In order to load rounds from the main ammunition rack, help from the rest of the crew was needed. The turret was also very cramped. The diameter of the Cromwell's turret ring was only 1524 mm, compared to the T-34-85's 1600 and M4 Sherman's 1753 mm. As for the driver's compartment, it was also deemed satisfactory.

Cromwell towing a T-34 on a forest road during trials.

The cramped turret was only the surface compared to the truly destructive verdict regarding its design. This verdict also applies to the hull. While even Japan already started using entirely welded designs, British tanks were still assembled on a frame made of 13 mm thick steel, which the armour was riveted to. Only the front and rear hull plates were welded on to the side plates using angle brackets, which were riveted for additional robustness. Certainly, this method was more convenient for the Birmingham Railway Carriage & Wagon Company, but the Cromwell was not a wagon or a cistern.

The turret plates were also riveted to a frame. The outside, with its massive protruding rivets, was unmistakable, but this offered little solace to the crew. The tank's case worsened due to its blocky hull. It seemed that the tank's designers knew nothing of the T-34 and its sloped armour plates. Long story short, the evaluators had nothing good to say about the Cromwell's hull and turret.

In the winter of 1945, tank number T.187866 was partially disassembled and shot at.

During the first stage of the trials, the tank travelled 128 km. The maximum speed obtained was 52 kph. In the same conditions, the M4A2 Sherman reached a speed of 48 kph, and the T-34 reached 55 kph. The tank handled easily. However, the Cromwell spent a lot of fuel. Over 100 km, it consumed 280 liters, while the M4A2 consumed 180 liters and the T-34 170 liters.

Full trials began in late October and lasted until the end of the month. During this time, the tank travelled 340 km on an asphalt road, 1339 km on dirt roads, and 152 km off-road. The average speeds were 44.7 kph, 22.7 kph, and 24.3 kph respectively. On a highway, fuel consumption reached 225 liters for 100 km, on dirt roads 353 liters, and off-road up to 370 liters. Comparative trials off-road and on swampy terrain showed that the Cromwell's narrow tracks make it perform poorly when not on roads.

The front plate of the Cromwell after taking fire from the German 75 mm KwK 42 L/70 gun used by one of its main adversaries, the Panther.

The results of the trials were less than satisfactory. Yes, the Cromwell IV was the best tank made in Great Britain at the time. The problem was that the "Englishman" was inferior to the Sherman in all respects except speed. Supplies of the M4A2 with a 76 mm gun in late 1944 further widened the gap. The conclusion was obvious: "The Cromwell IV tank cannot be recommended for import." Tanks and their components were spread out over various factories and institutes. Tank number T.187887 remained at Kubinka and can now be seen at the Patriot park.

In the winter of 1945, tank number T.187866 was partially disassembled and shot up. It turned out that the front plate could protect from Soviet ZiS-3 and F-34 guns, but the sides could be penetrated from over two kilometers. Of course, the odds of meeting a T-34 were much lower than those of meeting a Panther, whose gun penetrated the armour of the tank at any distance.


  1. Easily accessible information on Cromwell is harder to find than the Sherman or T-34, but this is a pretty damning indictment!

    1. There's also this British report of "Exercise Dracula" in '43 over at The Chieftain's Hatch:

      It's fairly scathing; the reliability/maintenance angle is a particular sticking point. :/

  2. "The target for the Cromwell was a Tiger E. At 500 and 600 meters, the M61 shell penetrated the side of the turret completely. At 650 meters, the shell made a 75 mm deep dent and two cracks. To compare, the 75 mm American gun on the M4 Sherman could penetrate this armour at 640 meters, and the 76 mm F-34 couldn't penetrate it with a stock shell at 100 meters."

    But according to the superior American gun couldn't get 75% of its projectile through an 80mm plate at 100m.

    1. IIRC that chart has the M3 Lee's gun tested, with the L/31 M2 rather than the L/40 M3 the Shermans use. Assuming both tests were with the heavy capped round and the "overcharge" propellant load, the increased length on the Sherman's gun could increase velocity enough to do it.