Monday, 25 October 2021

A Questionable Finish

The American tank industry finished WW2 in a strange position. On one hand, the Americans achieved an impressive amount. Starting the war with a few hundred light tanks and a few dozen medium ones, the Americans quickly caught up and in some ways even overtook the leading tank building nations of the world. The Medium Tank M4 was one of the finest medium tanks in the world when it was built. The Americans also achieved great things in SPG development. However, the Americans were in a difficult position by the end of the war. The looming crisis was not so obvious in 1945, but if one digs a bit deeper then the situation in American tank building begins to seem a lot more dire.

Achievements of the arsenal of democracy

It's wrong to say that everything was bad with American tank building. Overall, the Americans came at least third and were leaders in some aspects. Before talking about problems, it's worth listing their achievements. This can also show where the problems came from.

Like the Soviet T-34, the Medium Tank M4 remained the main American tank until the end of the war.

By 1943 the situation in American tank building was far from ideal, but better than what was happening to the Germans. The combat debut of the Medium Tank M4 took place in the fall of 1942. This tank became the second most numerous tank of WW2. It was an evolution of a chassis that came about before the war. The decision to avoid changing it was wise, as it allowed production numbers to remain high. The Americans showed that they were adaptable and capable of quickly compensating for any difficulties. Production initially relied on radial aircraft engines, but by 1943 a whole series of engines were in use. The USSR solved its engine shortage by building several factories that produced engines from the V-2 family. Meanwhile, the Americans used four different types of engines in their medium tanks (there was also a fifth one used on the M4A6, but its age was a short one). The cost of this was the need to build a different hull, but four different manufacturers (Continental, Ford, Chrysler, and GM) solved the engine problem.

Recall also that the Americans built 49,000 Shermans in 3.5 years, while the USSR had from 1940 to 1946 to build 61,000 T-34/T-34-85. Tanks from the T-34 family were built at six factories in total (seven if you include factory #183 in Kharkov), but the Medium Tank M4 was built at a dozen different plants. American tank factories were also not working just for themselves, but also for the British, as over 17,000 tanks were sent to the UK.

M4A3E8, the peak of evolution of the Medium Tank M4. These tanks served for a long time after WW2 ended.

The Medium Tank M4 was the greatest achievement of the American tank industry. This workhorse had an impressive modernization reserve. Without much trouble the Americans installed a new turret on their medium tank, making a vehicle that was no worse than the T-34-85 and definitely better than the Pz.Kpfw.IV, its main opponent in 1943-45. The hull was also modernized, which improved the conditions in the driver's compartment, and the HVSS suspension solved the issue of increasing ground pressure. After the war it turned out that the Medium Tank M4 could accept even a 105 mm gun thanks to its 1750 mm wide turret ring, a record in its class. To compare, the Pz.Kpfw.IV expended its modernization resource by the end of 1942. The fact that the modernized M4 chassis was suitable for the next generation of SPGs was also important. Some of them entered service right at the end of the war.

The Light Tank M24, the best light tank of WW2, served even longer.

The Americans were even more successful at building light tanks and SPGs. It helps that these tanks were not intended to be cheaper and smaller medium tanks, but rather used for reconnaissance and other special tasks. Development hit a snag with the Medium Tank M7, but went a different way after the desire to have thick armour cooled off. The Light Tank M24 ended up being not just the best light tank of WW2, but also a good platform for SPGs. These SPGs did not make it in time for WW2, but came in handy in Korea, where they achieved great results. The use of light tanks for SPG chassis became a priority for the Americans later on.

Gun Motor Carriage M36, the best tank destroyer the Western Allies had at the end of the war. This vehicle was often used as a tank, since it was not much different from one conceptually.

Medium tank destroyers were also a successful direction. Tank Destroyer Command backed projects like the GMC M18, but practice showed that this was not the right move. Its armour was not even thick enough to protect from heavy machine guns. It was also impossible to install any gun heavier than the 76 mm M1 on this chassis. There were some experiments, but all ended as failures. On the other hand, the GMC M36 ended up being the best American tank destroyer. This vehicle was not built from scratch, but rather as a conversion of the GMC M10, M10A1, or the Medium Tank M4A3. This optimization allowed rapid production of these tank destroyers which were also often used instead of tanks,

The Heavy Tank T26E3 ended up as the only new generation tank that managed to see battle.

The Americans were the only ones among the Allies who managed to not only build a next generation medium tank, but use it in battle. This was the Heavy Tank T26E3 or M26. It took a great effort to create this tank, but recall that the T-44 was also mired in adversity and never made it to the front anyway. The British Centurion also came too late to fight. The T26E3 was not without issues, but it performed quite well in the last year of the war and served for some time after that. Many American tanks built in the second half of WW2 ended up with quite long careers. Many of them were only retired in the 1950s, and other nations continued to use them for much longer. The Light Tank M24 and Medium Tank M4 finally retired not too long ago.

Half a step behind

We did not start with 1943 by accident. This year was the most difficult for American tank building. Failures were experienced in several directions at one. For one, the heavy tank program hit a dead end. The Heavy Tank M6 was deemed to not meet modern requirements, and thus not built in large numbers. The program to create a new light tank ended with a new medium tank, as mentioned above. This delayed the debut of the new light tank by a year. This was not such a big problem, as light tanks were used for secondary objectives, but the medium tanks were a bigger issue. The Medium Tank T20 concept was solid, and the tank was modern for its time. Nevertheless, it paled in comparison to the Panther. The same can be said for the Soviet T-43.

The late appearance of the T26E3 is simple to explain. The tank was the result of the fifth attempt to build a new vehicle, and the new tank was already pushing the limits of its chassis.

Reliability was the biggest issue of the Medium Tank T20 and its family. Various defects cropped up regularly. Each vehicle had its own Achilles' heel: an unreliable transmission, overloaded suspension, complex electrical system, etc. The result was a false start in the form of the Medium Tank T23 that was even accepted into service, but turned out to be too complicated for front line service.

Suspensions also caused a lot of headaches for the Americans. It was clear that the torsion bar suspension was optimal after they had the chance to inspect the Soviet KV-1 and German Pz.Kpfw.III. This suspension was relatively quickly introduced to light tanks, but medium ones were harder. The same was true for the Medium Tank T25E1 with its new 90 mm gun. Interestingly enough, the Medium Tank T26E1 was the most successful tank of the family, since it was built with a reinforced suspension from the start. The tank was now officially a heavy, not just because it weighed 40 tons compared to the Medium Tank T20's 30, but also because it had tougher front armour than the Tiger

In Korea the Pershing was famous for its amount of technical issues.

The Heavy Tank T26E1 ended up as the leader in the race for a new medium tank, but with a number of caveats. Yes, this was the most reliable tank in its family, but nowhere close to the level of the Medium Tank M4. The Ordnance Department was aware of this, and so "Zebra Mission" (the operation that included the tank's combat debut) included a large amount of technical support. The tank's reliability became a problem in Korea when 60% of losses were caused by breakdowns. American tankers considered the more reliable M4A3E8 to be the best tank of the Korean war, not the M46 Patton, the Pershing's successor. Of course, the conditions in Korea were different, but the reliability was an interesting factor. The Pershing also had other issues.

The first battles showed that the Heavy Tank T26E3's armour is insufficient. It later turned out that it was impossible to improve it any further,

As mentioned above, the Heavy Tank T26E1 and Heavy Tank T26E3 were built with the Tiger's armour in mind. Unfortunately, 4" of hull armour and the 4.5" thick gun mantlet turned out to not be enough. The first battle between the two tanks ended up with a knocked out Pershing. The Tiger was not even its most dangerous opponent. The Panther was the Pershing's equivalent by weight, but it had superior armour to the Pershing. The Pershing could only knock out a Panther from over a kilometer away by the very end of the war, while the Panther could knock out the Pershing at a larger distance. Officially, the Pershing's armour protected it only from the 75 mm Kwk 40 L/48, and even then not at all ranges. The American tank did not catch up to the Panther. Furthermore, there were no reserves for thickening the armour. The M46 Patton was merely an improved M26. The tank's mobility improved due to a more powerful engine, but some of the Pershing's design flaws persisted. Even the Patton's reliability was far from ideal in the Korean War.

Heavy Tank M6A2E1, a desperate attempt to build a heavy tank. This tank used the stock turret of the Heavy Tank T29.

There were plans to build 6000 of these tanks. This required production of 600 M26es monthly. While Fisher Tank Division managed this figure, the Detroit Tank Arsenal delivered just over 150 tanks at the best of times. Even if production of the M26 didn't end with the war, the 6000 unit mark was still unattainable. The Medium Tank M4 remained the main American medium tank. This was also true for the USSR, where the T-44 did not replace the T-34-85, and the T-54 had to be polished over the course of five years. The T-34-85 only stopped being the USSR's main tank in the 1950s.

Super Heavy Tank T28, the heaviest and most useless American tank,

The problem was that the Americans had nothing better than the Heavy Tank T26E3. As a result, projects that started multiplying like rabbits after the discovery of the Tiger Ausf.B were all based on the T26E3. There was also an attempt to breathe life back into the Heavy Tank M6, although the Heavy Tank M6A2E1 built by the end of the summer of 1944 was nothing more than a mobile test lab. The Ordnance Department also tried to make something out of the Super Heavy Tank T28 project. This vehicle was reclassified as the Gun Motor Carriage T28 since it had no turret in February of 1945. The result was the heaviest, best protected, and slowest American vehicle of WW2, and also the most pointless. It must have been built only out of stubbornness. 

The Heavy Tank T26E4, the only true American heavy tank to see front line service. 

There were six more heavy tanks in development in the spring of 1945 in addition to the M6A2E1 and T28, some of which were based on the T26E3. The Ordnance Department set up a sort of a race, hoping that at least one tank would make it into battle. In part they were right, the Heavy Tank T26E4 ended up on the front lines in March. It was heavy only from the point of view of armament, although the 3rd Armored Division gave it additional armour. This tank saw battle and even beat some opponents. It was even mass produced, although the order for 1000 tanks was cut down to just 25. The second "upgrade" was the Heavy Tank T26E5, which had improved production rather than armament. This tank was not produced in large numbers and did not see battle. It turned out that the cost of thicker armour was not just mobility, but also reliability.

Heavy Tanks T29 and T32, both unsuccessful attempts at building a heavy tank on the T26E3 chassis.

There was a third variant of the Pershing that combined both improved armour and armament: the Heavy Tank T32. The idea was not a bad one, but its authors forgot one important thing. The result was a brand new tank rather than an upgrade of the T26E3, which further pushed out the deadline. Rather than a new batch of M4A3E2s that the army wanted the result was one prototype that appeared months after the fighting ended and another that appeared in January of 1946. By then this tank was about as useful to the army as an umbrella to a fish. The armour was indeed strong enough to resist the 88 mm Pak 43, but the gun of the Heavy Tank T32 still couldn't penetrate the front of a King Tiger, not to mention the absolute nightmare that trials turned into. The chassis had to be fundamentally altered and the new components were quite ill-mannered.

Trials showed that the tank was quite unreliable. The 105 mm T5E1 gun was also not a reliable means of defeating the latest German tanks. The American heavy tank was still worse than the King Tiger.

The story of the Heavy Tank T32 is not as disappointing as the "Big Three": Heavy Tanks T29, T30, and T34. Work on these tanks began in August of 1944. The first tank was the Heavy Tank T29 armed with the same 105 mm T5E1 gun as on the Heavy Tanks T28 and M6A2E1. An alternative with a 155 mm T7 gun turned up almost immediately. As for the Heavy Tank T34, work began in January of 1945. It differed from the T29/30 due due to its 120 mm T53 gun with AA gun ballistics. In everything else the tanks were identical. The designers didn't want to make their lives difficult and started with the Heavy Tank T26E3 and its 102 mm thick front armour. The result was quite strange: the tanks had up to 280 mm thick front turret armour and a hull that was only thick enough to resist the 75 mm Pak 40 and KwK 40. This kind of approach is puzzling.

The Heavy Tank T30 had a more reliable engine, but its gun was not a good choice.

The weak front hull armour was only one problem with the T29/T30/T34 family. The army was eagerly awaiting these vehicles. The Ordnance Committee ordered 1200 Heavy Tanks T29, which shows how badly the army needed these tanks. In reality, only two turrets were built in 1945 (and were installed on the Heavy Tank M6A2E1). The results of trials of those turrets were far from idea. Time went on and the plans for production of the T29 radically changed. On August 23rd, 1945, the Ordnance Committee cut the order at Pressed Steel Car Co. from 1152 units to two, one of which was not assembled completely.

The work then moved to the Detroit Tank Arsenal. All materials on the heavy tank were transferred there. The arsenal built 8 of these tanks. By 1946 it was clear that it was not useful for anything but experiments. In reality the first of these tanks were only delivered in 1947 and the trials turned into a real battle with the engines and transmissions.

Power pack with a Continental AV-1790-1 engine and CD-850 transmission, the best outcome of the Heavy Tank T29/30/34 program.

One of the biggest issues of the "Big Three" was that there was no reliable engine or transmission for these vehicles. A power pack with a 12-cylinder Ford GAC engine and EX-120 transmission was quickly designed, but trials of the Heavy Tank T32 showed that the EX-120 was quite unreliable. As for the Ford GAC with its roots in aircraft engines, it worked well on the 54 ton T32, but constantly broke down when it came to the nearly 65 ton Heavy Tank T29. The T29 would not have made it into battle by early 1945 even if the American tank industry made an impossible leap forward.

As a result of trials of the Heavy Tank T32 Allison urgently created the CD-850 transmission. It took two years to polish the design. As for the engine, the Continental AV-1790-1 was the victor among three potential engine types by 1948. The 120 mm T53 gun was chosen as the victor years after the tank it was put into was abandoned. It's hard to call the development of the next generation American heavy tank anything but a complete failure. Compared to this, post-war struggles of Soviet heavy tank builders look like minor inconveniences.

Another outcome of the Heavy Tank T29/30/34 program: the T53 gun that evolved into the M58. This gun was later used on the Heavy Tank M103.

The summary of all these events is not flattering. The Americans failed colossally. Development of heavy tanks ended with nothing and attempts to create a new medium tank resulted in a small modernization accepted into service in 1944.

"Cut up the excess"

The tank drama is only one fragment of the overall picture in American armour manufacturing towards the end of WW2. The development of new tanks didn't mean that other programs with even longer timelines didn't exist. Armed forces in different nations often have the same opinions about the same processes. A great example is the investigations conducted by the AGF (Army Ground Forces). This organization had its own special opinions about some types of armaments and military vehicles. For instance, the considerable delay in the production of the GMC M36 was their fault. As a result the best American tank destroyer appeared on the front lines only in October of 1944 and not in June.

A tank destroyer on the Medium Tank T23 chassis. This vehicle did not proceed past a model since the 90 mm gun could be used on the GMC M36. In early 1946 it turned out that tank destroyers were no longer needed.

The AGF launched its own research program into the future of armoured vehicle development on January 2nd, 1945. It was headed by Lieutenant Colonel Frederick C. Brecket from the Armored Medical Research Laboratory in Fort Knox. It was strange that this job was assigned to a man who did not work with tanks directly. Nevertheless, the report completed by June 2nd, 1945, was quite interesting. Brecket obtained information on the status of the tank industry, newest developments, and information on the enemy's armoured vehicles.

The end result was reminiscent of something. He concluded that the army needed tanks that weighed 25, 45, 75, and 150 short tons, or 22.7 tonne light tanks, 40.8 tonne medium tanks, 68 tonne heavy tanks, and 136 tonne superheavy tanks. This was quite similar to the infamous E series, but without the E-10 tank destroyer and a light tank instead of the E-25. Brecket also favoured small caliber guns with high muzzle velocities, same as the Germans. 

Chrysler K, an attempt to make a new heavy tank that was quickly cancelled.

Brecket's proposals were never built in metal, but the attempt itself showed that the American tank program was lost. The new generation of SPGs was also stuck. While the SPGs on the Light Tank M24 chassis were simply too late to fight in the war, SPGs on the T26E3 chassis just didn't turn out. The situation with tank destroyers also stagnated, especially since the tanks and tank destroyers ended up having the same armament. The Americans were not alone in this, as a similar situation developed in other nations.

The Light Tank T37, one of the outcomes of Stillwell's Council. This vehicle later evolved into the Light Tank M41.

The War Department had to unpack all this nonsense. The War Department Equipment Board formed on November 1st, 1945. It was better known as Stilwell's Council, headed by Joseph "Vinegar Joe" Stilwell. This general had a very harsh reputation, but his suggestions were reasonable. The board prepared a list of items that were high priorities for American tank building in the first five years after the war on January 16th, 1946.

To start, the ideas of superheavy tanks, tank destroyers, and anti-tank artillery were done away with. The first item needs no explanation. As for the second, the board concluded that a tank is the best tank destroyer. The board also suggested development of new specialized tank engines, which Continental successfully did. Development of a new generation light tank (the Light Tank T37) and SPGs on its chassis (155 mm HMC M44 and 105 mm HMC M52) was also launched.

The War Department Equipment Board launched the development of new tank engines.

Even though the board did not exist for long in its initial form (Stilwell died on October 12th, 1946) it had a lot of impact on the development of post-war American tank building. The late 1940s were spent working on new components (largely new engines and new armament). The 90 mm M3 and its derivatives remained the main weapon of American medium tanks for a long time. The qualitative leap of the early 1950s would not have been possible without this preparation. In many ways this leap was also triggered by the Korean War that broke out in 1950.


  1. This article peddles some basic, verifiable falsehoods and needs to be corrected.

    Yuri pashlock is either speaking from ignorance or lying about the armor of the T29 heavy tank and its relatives. He speaks of its 102mm of armor without remotely accounting for the slope of the armor. Its sloped at 54 degrees from normal, giving it a equivalent thickness of 170 ish mms. This can resist far more than the piddly 75 L48 panzer IV popgun. This armor is impenetrable to the PAK 40, the kwk 8.8 L/56 of the Tiger, and the kwk 7.5 L/70 of the Panther. It even stands up well to the kwk 8.8 L71 BECAUSE THAT IS THE GUN IT WAS DESIGNED TO RESIST.

    Also, he states that Panther can defeat pershing at greater ranges than vice versa. This is also wrong. It is well known that T33 ammo could bust a Panther at over a kilometer, but the Panther would have trouble with the 145mm of effective armor even at half a kilometer. You can argue that Panther can defeat the pershings turret at range, but the opposite is also true. He then states that there were no reserves for increasing the armor before admitting a paragraph or two later that oh yeah, there is a very heavily armored Pershing.

    By God, this article is embarrassing. Usually Yuri does good work but with this turd, I'm going to have to watch everything he does like a hawk.

    1. Hey that's almost my exact thought as well.
      I pretty much wanted to write exactly that xD

    2. I thought the effective frontal turret armor of the Pershing to be more like 200 mm (114 mm mantlet over 102 mm turret, plus being rounded there are slope effects). The largest part of the front hull is 102 mm @ ~45 degrees, which is over 170 mm effective. The lower hull is only 76 mm sloped at about an average of 40 degrees, so maybe it's like an effective of 120 mm, but lower hull hits are rare. The Pershing is a somewhat rare tank in that the front turret is tougher than the front hull (which makes it ideal for hull-down positions).

      That's not the armor protection of an IS-3, it's not a King Tiger (though the armor quality may be better) and I even wouldn't rank it as high as an IS-2 model 1944. But it's not terrible, and way better than either the Tiger I or Panther. I'm with you, I like the US 90 mm's APCBC round against the Panther's front better than I like the Kwk42's round against the Pershing's front.

    3. Yeah, I was irritated that he somehow said the Panther carries more armor than the Pershing - while the Pershing has more armor on literally every surface both in raw thicknesses and in line of sight terms.

      And if Yuri wants to play the game of US armor castings having big faults in WW2 (they certainly did), he's going to have to forget all he's written about the numerous constructional and metallurgical failures in Panther armor.

  2. Is there somewhere a good book or something about tank engine development? A lot of countries seemed to struggle to produce a good tank because they lacked the right engine

  3. “ The result was the heaviest, best protected, and slowest American vehicle of WW2, and also the most pointless.”

    Well, I still like the Doom Turtle, so there.