Monday, 21 December 2020

The Best of the "Varangians"

The first American Lend Lease tanks arrived in the USSR towards the very end of December 1941. The volume of shipments was small at first, but this changed in the spring of 1942. American light and medium tanks began arriving in large amounts and were widely used in battle by that summer. The Medium Tank M3, known as the M3S or M3sr, was the most common American medium tank shipped in 1942, but towards the summer the Americans began to shift production to the more successful Medium Tank M4. Its diesel variant, the Medium Tank M4A2, became the most common foreign tank used by the Red Army.

A complicated American

The diesel powered Medium Tank M4 came about due to the vastly increased demand for medium tanks. They were built not only for the Americans, but also for the British. The American diesel tank was largely meant for the British. They initially wanted to produce the Matilda tank at American factories, but the Americans refused this proposal after examining the tank. A decision followed to produce special variants of American tanks for the British.

The most famous such tank was the Grant I, created in part by L. Carr, a tank specialist from the Department of Mechanization. He was also the father of the American tank diesel engine. The GM 6-71 2-stroke water cooled 6.98 L engine was chosen as the optimal candidate. This engine was used on buses initially, but during the war its applications became broader. A pair of these engines indexes GMC 6046 was used first on the Medium Tank M3A3 and M3A5. These tanks never saw battle, but the fate of the next diesel tank, the Medium Tank M4A2, was different. The Fisher Tank Arsenal delivered the first vehicles of this type in April of 1942. Due to a high level of parts commonality changes to the chassis were minimal. The biggest changes had to do with the rear hull plate and engine deck. Five different factories produced the M4A2. 8053 tanks of this type were produced until May of 1944, of which 4616 (more than half) were built at Fisher.

Assembly of a Medium Tank M4A2 at the Fisher Tank Arsenal, summer of 1942. The first M4A2 tanks to arrive in the USSR were of this type.

The Americans had no need for a diesel tank. The Army used gasoline engines and diesel was more common in the Navy. It's no surprise that the US kept just 640 tanks of this type. A large amount of the these was used by the Marines. As for the others, the majority (5041 tanks) was sent to the UK. The Sherman III as they called it became the second most common foreign tank behind only the Sherman V (M4A4). 

As for the USSR, they first heart of the Medium Tank M4 in November of 1941 when trials of the Medium Tank T6 were still underway. The intelligence summary reported that a diesel engine was under development. More detailed characteristics became available in April of 1942, but they only described the Medium Tank M4A1. Information about various engines for the M3 tank arrived in mid-May. The USSR rejected nearly all of them, with the only exception being the M3A4. According to their information, it was equipped with "two 2-stroke diesel engines, 210 each, same as used on the Canadian "Valentin 7" tank). In reality, the M3A4 was equipped with Chrysler A57 Multibank engines, the M3A3 and M3A5 were the ones with diesels. The GABTU's decision on this matter is interesting. They opted to order 100 of these tanks per month to gradually replace the M3s with gasoline engines.

The first 26 M4A2 tanks arrived in the USSR in November of 1942 as a part of Operation FB.

Deliveries of the diesel powered Medium Tank M3 never happened, but the GABTU began a storm of correspondence regarding the Medium Tank M4. The GABTU wanted to know if it was possible to equip it with a diesel engine. By mid-August, the GABTU was in touch with the People's Commissariat of Foreign Trade. Realistically minded tankers wanted to know if the tanks can be equipped for winter. The USSR already learned about the M4A2 at that point. Unlike the Medium Tank M3, the new tank was only called M4A2 in correspondence (the name "Sherman" was not used in either letters or front line reports). There was only one exception: in May of 1943 a representative of the British Military Mission in the USSR Lieutenant Colonel Turner offered Sherman tanks to the USSR. Essentially, the British were reselling the same tanks that they got for the Americans. It is not clear how this proposal ended up, but there are serious suspicions that there were some Sherman IIIs among the tanks delivered to the USSR. Delivery of sand coloured vehicles and some with heavy wear was recorded, but more about that later.

Installation of the British Wireless Set No.19 in the Sherman's turret bustle. These radios were installed in the USSR en masse.

The Soviet interest in the winterization of the M4A2 was ill-fated. A months-long pause in deliveries followed the destruction of the infamous PQ-17 convoy. PQ-18 set out only in the fall of 1942. American tanks reached the USSR much later, during Operation FB in November of 1942. The British tried a new tactic with singular ships. Although the operation was deemed a failure and they returned to the previous practice of full blown convoys, these ships still delivered a large amount of vehicles to the USSR, including 26 M4A2 tanks. The next batch of 10 vehicles arrived through the southern route by the end of December.

The tanks that came in through the north were sent to the Gorky Armoured Vehicles Center, although not right away. Issues with injectors were discovered quickly. These broke after 5-10 hours of work. An investigation followed which Americans were involved in almost immediately. It turned out that there were three different kinds of injectors. The S type meant for Valentine tanks (140 hp), A type for tractors (165 hp), and M for GM 6046 engines (220 hp). Issues arose with M injectors. Attempts to use S injectors were made. Reliability was not significantly affected, but speed dropped by 10-15% and fuel expenditure rose by 12-20%. The Americans offered to retune A type injectors and start shipping those. Several hundred injectors were sent to the USSR by aircraft.

M4A2 tanks shipping out to the front lines, September 1944. The tanks had dust shield equipped, but like in the American army these did not stay on for long.

Further investigation discovered that the engines were being used incorrectly. However, this was the American theory. The Soviet theory was different. Study of defective engines revealed low production quality of some components. The spare pistons and rings appeared to be hand-tuned, which raised some questions. There were also other issues that arose during the winter. All this led to tanks that were shipped through northern convoys not being ready for battle until the summer of 1943.

Later events confirm that the American side was not entirely honest. Out of 29 tanks that arrived through the south in May-June of 1943, 13 had defective radiators. Tanks arrived with locks, but without keys, so the locks had to be broken off. The Americans themselves later admitted that there were manufacturing problems with their injectors. Information about use of the M4A2 in the US also seeped through, and their experience was also far from perfect. It turned out that many turrets were poorly fitted, most radiators were leaky, ball bearings in road wheels were defective. Defects with drive sprocket crowns coming off were widespread. Furthermore, the sheet metal shield that was supposed to deflect exhaust turned out to be an excellent ramp for bullets, deflecting them upwards into the radiators. This information came in January of 1944 from Major General Deane, the head of the American Military Mission in the USSR.

Sketches of old and new M4A2(75) tanks made by Soviet military QA, summer of 1944.

Further deliveries of the M4A2 were a mere trickle, especially compared with the M3. 26 tanks arrived in January of 1943 (20 through the north via convoy JW-51A and 6 through the south), 69 in February (all through the south), 9 in March (all through the south), 9 more in April (all through the south), 52 in May (all through the south). Deliveries then ended for half a year. This is easy to explain. The USSR was allocated about 200 tanks (211 arrived in practice) assembled in July-August of 1942. After that the American tank industry had no time for the USSR. They had their own army and the British to worry about. The peak of production for the British lasted from February to July of 1943, after which American factories switched to supplying the Soviet Union again, albeit with some pauses. Including the 3-4 month lag between production and delivery, the USSR received only Canadian Valentine VII tanks between June and October of 1943 that the British themselves had no need for.

Deliveries resumed only in November of 1943, and a large portion arrived through a strange route. 149 M4A2 tanks arrived in Vladivostok while only 32 arrived in Baku. 45 more came in through the south in December. There are no precise records of northern convoys for this period, but based on overall deliveries for 1943 (469 by the GBTU's count) only 78 tanks came through here in November-December of 1943. Vladivostok was not used as a transit point for foreign tanks for long. Only 229 tanks came through here, 80 of which came in the second half of 1944.

Modernized M4A2(75) tanks began arriving in the USSR in July-August of 1944.

Full fledged deliveries of the M4A2 began in 1944. Only 4 tanks arrived in Baku in January of 1944, but 64 came in February, 97 in March, 137 in April. The northern route was the main delivery method. 800 tanks were delivered via Baku in 1944, but 1465 came through the northern convoys. Not all of them were M4A2, as delivery of the M4A2(76)W began in late September of 1944. Since the delivery records did not distinguish the two, it is hard to arrive at an exact number of M4A2 tanks delivered. The GBTU's records only add more confusion, as their numbers differ. There is also no difference between the M4A2 and M4A2(75). Soviet QA discovered the change only in the summer of 1944. According to American sources, 1990 tanks of this type were sent to the USSR.

QA logged changes made to the arriving tanks since November of 1943. Changes included a new air cleaner, applique armour on the sides, metallic tracks, and the disappearance of the Thompson SMG from the tanks. M4A2 tanks with 51 mm breech loaded mortars began arriving in December. Alarms rang in Baku when in late April of 1944 heavily used tanks arrived in the USSR. It's hard to tell whether these were formerly British tanks or American tanks used for training. Complaints about incomplete equipment were also common. These were sometimes filed by Soviet units, but equally often missing tools were noted on tanks that just arrived in the USSR.

Modern and reliable

One M4A2 tank that arrived in November of 1942 was sent to Kubinka, where the NIBT proving grounds had returned by then. The tank with registration number U.S.A. W-3021079 produced at the Fisher Tank Arsenal in August of 1942 was selected for trials. Unlike the Medium Tank M3 that waited for almost half a year for trials, its replacement did not have to wait. The tank embarked on trials by December 19th, 1942.

The M4A2 tank at the NIBT proving grounds, December 1942. This tank has metallic T49 track links equipped.

The condensed winter trials program spanned 500 km of driving: 100 on a highway, 250 on a dirt road, and 150 off-road. Since the tank had rubber tracks without grousers, trials with removable grousers installed would be conducted separately. Crew comfort, reliability, and convenience of ammunition storage was tested. The gun stabilizer was tested separately. A technical description of the vehicle was composed in parallel with trials.

The testers noted that the tank was quite tall.

The new American tank piqued the interest of specialists at the proving grounds. Unlike the M3 medium, which had a riveted hull, the M4A2's hull was welded together. Testers also noticed that it was lower, although it was still quite tall. The fighting compartment and driver's compartment were laid out completely differently. Even though the running gear migrated over from the M3, there were sill some differences. Also unlike the M3, which had an uncomfortable AA cupola, the M4A2 had a Browning M2HB .50 caliber machine gun on a pintle mount on the commander's cupola.

The tank had a large amount of observation devices, which resulted in good visibility.

The tank drove for 74 km before trials began and 665 more between December 19th and February 8th, 1943. The tank was tested with two sets of tracks. The first 421 km were covered with metallic T49 tracks that didn't need removable grousers. With them, the M4A2 drove for 203 km on a highway, 92 km on dirt roads, and 126 km on snow off-road. After that, the stock T41 tracks with removable grousers were reinstalled, after which the M4A2 drove for 117 km on a highway, 73 km on dirt roads, and 54 km off-road. Regular diesel fuel was used. American oil in the engine was replaced with Soviet EL oil, but in the transmission American oil was retained.

The M4A2 can be distinguished by the shape of the rear plate and presence of mufflers.

The M4A2 drove in rather severe conditions. The air temperature was between -12 and -22 degrees. The winds were high and transitioned into blizzards. The highway used for testing was covered in packed snow. Nevertheless, the tank reached a speed of 45 kph on steel tracks. This was just 3 kph lower than top speed stated in the manual, although it couldn't hold it for long either way. The top speed on rubber tracks with grousers fell to 31.8 kph. The problem here was the grousers, although the Medium Tank M3 with the same tracks and no grousers only reached a speed of 32.4 kph. The average speed of the M4A2 with metallic tracks was 29.1 kph, fuel expenditure was 195 L per 100 km. On rubber tracks the speed fell to 25.6 kph, fuel expenditure rose to 306 L per 100 km. The difference between diesel and gasoline engines was already obvious. The Medium Tank M3 used 387 L per 100 km of fuel on the highway without grousers and 582 L per 100 km with them.

The gun stabilizer attracted some attention. Trials showed that it improved precision when firing on the move.

The M4A2 also showed itself well on dirt roads and in snow up to 40 cm deep. In these cases the average speed on metallic tracks was 22.4 kph and 19.1 kph on rubber tracks with removable grousers. Fuel expenditure was 268 and 396 L per 100 km respectively. In these conditions, the M3 consumed between 570 and 715 L per 100 km.

The high caliber AA machine gun was also a welcome addition.

Driving off-road in snow up to 40 cm deep was the toughest trial. The average speed with the two types of tracks was 17 and 16.5 kph respectively, fuel expenditure was 350 and 474 L per 100 km. The difference between the M4A2 and M3 grew greater. With grousers, the latter consumed 965 L of fuel per 100 km. The M3's average speed on a dirt road was the same as what the M4A2 could achieve with metallic tracks off-road. Cases of broken off grousers were recorded, most often when driving on the highway. Installing grousers every 5 track links improved traction, but pressure on the grousers increased and they broke off quicker. The metallic tracks with parallel bar grousers were not perfect either. The tracks became packed with snow during the trials, after which the tank slipped on a snow covered road, fell into a ditch, and flipped over.

Off-road mobility was high, but only with grousers.

Trials showed that both types of tracks give similar results off-road, with the exception of special trials. The tank could climb a 15 degree slope with metallic tracks but a 25 degree slope with rubber tracks and removable grousers. The Medium Tank M3 with rubber tracks and no grousers showed the same result as the M4A2 with metallic tracks. Rubber tracks with grousers also showed better results when driving at a tilt. They could be used at an angle of up to 22 degrees, while the steel tracks slipped after 17 degrees.

The tank flipped over during mobility trials.

Overall, the tank was reliable. Only three breakdowns were recorded during the trials, and none of them were related to injectors. However, the proving grounds specialists noted some issues. Water drained from the cooling system directly into the tank, which resulted in the formation of an icy crust that locked the control rods in place. The observation periscopes became packed with snow during off-road driving. This was especially bad for the driver and assistant driver.

Driving up a slope with rubber tracks and removable grousers.

Visibility and crew conditions were studied separately. The dead zone from the driver's station was 14 m long, which was not that bad. The presence of a rotating loader's periscope was a bonus. Similar periscopes were installed in the driver and assistant driver's hatches. The gunner's periscope doubled as a gun sight. The visibility was deemed good, better than on the T-34, but the gun sight was not considered as good. It only had markings for AP shells and no way to introduce corrections in the vertical plane. The crew stations were reviewed highly. No issues were recoded with the gunner and commander's stations. The loader's biggest issue was the difficulty in taking ammunition out of the side racks. The description did not include the fact that the fighting compartment was enclosed in a turret basket, which made using the escape hatch in the floor difficult. No flaws were recorded in the description of the driver's station or his assistant's.

Diagram of turret blind spots.

Trials of the armament yielded interesting results. The hull machine gun had no sights, as per American tradition. The assistant driver fired at a 2 by 2 meter target from 100 meters, aiming with tracers and observing through his periscope. 86 bullets hit the target out of 100. The coaxial machine gun scored 85 hits out of 100 in the same conditions. Trials of the 75 mm M3 gun showed that the peak rate of fire is 20 RPM. The main gun was also fired on the move, with and without the stabilizer. Thanks to the stabilizer and good crew placement, the gunner hit his target 47% of the time with a rate of fire of 3.87 RPM. With the stabilizer turned on, the rate of fire increased to 5.17 RPM and the accuracy rose to 87%. The hydraulic turret traverse mechanism was also rated highly.

The same tank in the summer of 1943. Rubber tracks were reinstalled.

The M4A2 was given high grades. The tank measured up to the T-34 and surpassed it in some aspects. In the spring of 1943 it also turned out that the T-34's gun couldn't penetrate the side of the Tiger tank, while the 75 mm M3 gun could penetrate it from 400-650 meters. Of course, there were drawbacks. It was hard to service the tank in the winter, the hull was very tall, and the tracks had bad traction in mud. Nevertheless, the overall grade was high. There were also some features that Soviet tank designers were interested in, namely the turret traverse and stabilizer Factory #183 and ChKZ management requested one tank each for study. IS tanks were tested with an American turret traverse mechanism.

Driving on a tilt with metallic tracks.

This was not the end of trials for the M4A2. Summer trials began on May 28th, although they were stopped on June 3rd due to a breakdown. It took a while for parts to arrive and the trials only resumed on July 29th, lasting until August 18th. The tank was tested with two types of tracks again. Initial plans consisted of a 1700 km run, but the total volume of trials including the winter ones reached 3050 km. Destruction of road wheel tires was recorded starting at 1758 km and the right track made of steel links tore at 1930 km. There were also issues with the engine, as a result of which the trials were stopped for repairs. Regardless, the reliability of the tank was deemed to be high. Soviet tanks showed worse results in the same conditions. Testers noted that the American tank was easy to quick to service.

An attempt to drive up a 31 degree incline using rubber tracks and grousers.

Due to issues with the steel tracks, trials proceeded without them. The top speed on rubber tracks was 50 kph, higher than the official top speed. The average speed on a highway was 39.7 kph, and 20.1 kph off-road. Fuel expenditure was 167 and 246 L per 100 km respectively, resulting in a cruising range of 310 and 210 km.

A late production tank tested at the NIBT proving grounds in 1944.

As expected, mobility during the summer improved. The tank could climb a 25 degree slope on rubber tracks without grousers. The steel tracks turned out to have the same limit. With grousers the rubber tracks could be used to climb a 28 degree slope, but the traction was insufficient to go any higher. The tank could drive at a 23 degree tilt without grousers or 26 degrees with them. The M4A2 could also successfully tow an M4A4 tank that was being tested at the same time on a dirt road.

The same tank seen from above.

Conclusions differed little from the winter tests. Reliability and mobility were high. However, there was one unfortunate trend. Wear on road wheel tires was high when metallic tracks were used. American documents show that they had the same problems. It's not surprising that American tanks continued using rubber tracks until the metallic T47 track with an inner rubber pad was created.

Big, comfortable, reliable

The career of M4A2 tanks that arrived in the USSR different little from that of the M3. Tanks that came in through the north were sent to the Gorky Armoured Vehicle Center. There, they were assigned to the 190th Training Tank Brigade (5th Training Tank Brigade as of January 1943), from where they were issued to combat units. This was the case at first, but later the deliveries stalled due to issues with injectors. The first combat unit to receive M4A2 tanks was the 92nd Tank Brigade, which received 16 M4A2 tanks in December of 1942, but they were quickly returned due to technical issues. As of March 20th, 1943, the 5th Tank Brigade had 40 tanks of this type, 35 of which were operational and 5 were in repairs. Repair Base #97 had 4 M4A2 tanks. The first unit to use the M4A2 from northern convoys in combat was the 229th Tank Regiment. It had 31 tanks as of April 10th, 1943. Later, it received 8 more tanks. In the North Caucasus M4A2 tanks were issued to front line units almost immediately. 9 tanks were assigned to the 563rd Independent Tank Battalion on January 4th, 1943. On January 12th 2 tanks were sent to the 5th Guards Tank Brigade, and tanks from the 563rd battalion soon followed them. The 5th Guards Tank Brigade was the first Soviet unit to really used these tanks in battle.

Early 1944. One of the first M4A2 tanks that came in through the northern convoys after the break in the summer and fall of 1943.

The use of M4A2 tanks on the North Caucasus Front in the winter and spring of 1943 was rather rare. The first real use of M4A2 tanks in combat was in the summer of 1943 during the Battle of Kursk. The only unit with these tanks was the aforementioned 229th Tank Regiment. It is usually stated that it fought as a part of the 48th Army, but that is not the case. By early July the regiment was included into the 13th Army, which fought in the north of the salient. The regiment was supposed to support the 148th Rifle Division, but in practice ended up supporting its neighbour, the 74th Rifle Division. The regiment did not take part in the battle for Ponyri, remaining in reserve. The regiment lost 14 tanks burned and 17 knocked out between July 15th and 18th with 117 men lost. The report stated that tanks were chiefly lost after being hit with HEAT shells, which caused ammunition detonation that tore off the tanks' turrets.

Tanks from the 5th Guards Tank Army. They still have both dust shields and AA machine guns. According to reports, these were removed.

In addition to the report on performance in combat, the 229th Tank Regiment compiled a report on other characteristics of the M4A2, as they had many months of usage to report on. The tank was quiet and smooth to drive, but it had issues when driving at a tilt. There were cases where the road wheels would run up on track connectors, which resulted in damage to both the wheel and the connector. The rubber tracks also slipped in swampy terrain. The tank was easy to drive, but the turning radius was high. The armour was rated as good, but the tank presented a very large target.

The turret received mixed reviews. The front of it was good, but the rear was criticized. Hits to the rear would destroy the radio. The driver and assistant driver's direct vision ports were also criticized. These ports were removed in late 1942 and replaced with additional periscopes. According to the regiment, it was easy to use the tank, but repairs were difficult. Interestingly enough, there were no complaints about mass issues with injectors. The armament was satisfactory, but the HE shell was considered weak. Interestingly enough, these tanks had British Wireless Sets #19, but these radios were installed in the USSR rather than the UK. Overall, the tanks were deemed modern, sufficiently fast and armed, and reliable.

An M4A2 from the 8th Guards Mechanized Corps in Lublin. The AA machine gun was removed.

As shipments of the M4A2 tanks stopped in the summer and fall of 1943, their use was rare. Out of 505 tanks that arrived from November 1942 to December 1943 only 37 were lost irreparably. Half a year later the situation was very different. 1065 tanks arrived in the USSR in the first half of 1944 with 499 lost irreparably, 108 of which were lost in May and 127 in June. Total losses of M4A2 tanks for 1944 add up to 1145. This was the most out of any foreign tank, with the Valentine taking second place (776 tanks lost in 1944). These numbers show the role the M4A2 tank played in Red Army operations. The 3rd Guards Mechanized Corps had 110 M4A2 tanks by June 22nd, 1944, the 1st Mechanized Corps had 136 tanks of this type. The M4A2 was actively used in Operation Bagration and other operations. It was also used by independent tank regiments in cavalry divisions.

M4A2(75) tanks from the 6th Tank Army in Romania.

A report on the use of M4A2 tanks in tank corps dated August 1944 makes for an interesting read. The report considers the American tank a good weapon against infantry and anti-tank artillery. Its gun was too weak against enemy tanks: the Tiger could penetrate its front armour from 1.5 km while the M4A2 could only penetrate its side from 600 meters. The ammunition racks were not very convenient to use, as a result of which tankers often piled up ammunition on the turret basket floor. As for the AA machine gun, it was not used in battle and was stowed inside the tank instead. This was because the machine gun could not be locked in position and often got in the commander's way. It could also be removed without the crew noticing. Other units also report the removal of AA machine guns. Most photos of M4A2 tanks taken in 1944 do not feature the Browning M2HB.

The armour of the tank was considered hard and ductile. Cracks and spalling did not occur when it was penetrated. Unlike in early 1943, there were no complaints about injectors, but the engines often overheated due to misuse. There were also issues with the drive sprockets and peeling of the road wheel tires. Despite these issues, commanders of mechanized corps rated these vehicles highly. They were reliable in battle, capable of long marches, had good visibility and were comfortable for crews.

One of the first tanks to reach Vienna, March 1945.

The M4A2 was actively used by the Red Army until the very end of the Great Patriotic War. Only three tanks delivered to the USSR remain: two in Russia and one in the Ukraine. However, only a handful of surviving samples of other foreign tanks sent to the USSR survive as well.

1 comment: