RE: On German tank armor

This is the third and final response that will be made to the gaming blog, For The Record. They have written alot of misleading articles on the subject of WW2, so its only natural that they are made the target of a thorough debunking. FTR has been used as a platform to spread revisionist history to unsuspecting readers. One of the main culprits is the individual known as EnsignExpendible. He is a Russian emigre who owns the Red Army themed blog, TankArchives. In theory, the website is supposed to be a neutral resource that translates Soviet reports from WW2. In practise, however, these memos are often selectively filtered and interpreted, and are accompanied with unnecessary opinions from the author. TankArchives consistently exaggerates the performance of the Red Army during 'the great patriotic war', while deflating the performance of the Heer it fought against. This theme is present in nearly every single article featured on the website. When expounding his propaganda on FTR, EnsignExpendible makes extensive usage of his own blog to buttress his faulty arguments. He misrepresents the war on the eastern front to such an extent that it no longer bears any resemblance to reality.

Moreover, he has repeatedly been shown to be dishonest, mendacious, and exceptionally ignorant on certain subjects. In his whopper of an article, the Ensign seeks nothing less than to single handedly rewrite the entire historical consensus about Germanys tanks. His thesis is that from the beginning of the war to the end, the Reich was consistently churning out tanks with substandard armor. He rejects the mainstream theory that their armor quality only declined late in the war. TankArchives theory is that -get this- it was of low quality right from the start. How he came to this preposterous conclusion is anyones guess. In any event, his thesis is built on a mountain of stupidity, ignorance, and hasty generalisations. His poor understanding of metallurgy and ballistics has been demonstrated before, and this article will prove to be no exception. TankArchives has created a Potemkin village that gives off the illusion of strength and soundness where there is none. Much like the Soviet Union itself, it is a colossus that will shatter under the weight of its own inconsistencys.

TankArchives and his Soviet 

propaganda victory

The stupendous claim

Within his article, TankArchives summarises a number of Allied studys conducted on German tank armor. He cites two American metallurgical reports on the Panther, and three Soviet ballistics tests on the Tiger II, Tiger I, Panzer IV and Panzer III. In this way, he attempts to provide a sortof chronology on the quality of their armor, and determine whether or not there was a difference in the early and late war plates. His theory that German armor was of consistently low quality throughout WW2 is put to the test. He quotes a number of passages from the reports in question, showing the substandard and deficient nature of the sampled armor. To an uninformed observer who doesn't know better, TankArchives seems to successfully make his case. But his victorys is entirely illusory, and can only be maintained through the false consensus he builds. A closer examination of the relevant facts causes his entire theory to implode in on itself like a house of cards. To refute it is actually remarkably easy. All we need to do is look through the metallurgical reports that TankArchives cites as evidence, and see whether or their explanation for the flawed armor matchs up with his theory.

The first report he cites is Metallurgical Examination of Armor and Welded Joints from the Side of a German PzKw (Panther) Tank. Heres what it has to say: ''The extremely poor shock properties are traceable to the nonmartensitic microstructure resulting from hardenability inadequate to permit full hardening upon quenching. The steel has been heat treated to a tempered bainitic microstructure containing banded segregates rich in ferrite.'' It also says this: ''Inferior toughness as evidenced by brittle fractures and low impact resistance has been reported in several investigations of German armor that were 2"1 and greater in thickness. The inferior toughness was traced in some instances to an inadequate hardening treatment, and in others to temper brittleness combined with incomplete quench hardening.''

The second report he cites is Metallurgical Examination of a 3-1/4″ Thick armor Plate from a German PzKw V (Panther) Tank. Heres what it has to say: ''However it exhibited extremely low toughness (as indicated by the fracture and Charpy tests) making it susceptible to shattering under a shock type ballistic test. The inferior toughness was attributed to a combination of incomplete transformation to martensite upon quenching and temper embrittlement...'' It also says this: ''It will be shown that the extremely low toughness in the plate under investigation is a result, in part, of temper embrittlement, a factor which may have been partly responsible for the inferior toughness in the German armor previously investigated.''


The logical rebuttal

Theres alot of jargon being thrown around here, but the conclusions are damning. Both reports state unequivocally that the brittleness of the tanks armor was caused by improper heat treatment and quenching. The steel mills were unable to achieve consistent quality control with their armor, and were unintentionally churning out many flawed plates. Why does this matter? Because these issues have been explicitly documented to only have occurred from early 1944 onward. This fact by itself completely disproves TankArchives theory that Germany was churning out flawed armor plates from the beginning of the war to the end! This is the key point. Before 1944, there was no evidence whatsoever of problems with armor quality. Whereas after 1944, it has been well documented that steel mills were unable to maintain quality control of their armor. And we know precisely what caused this decline, too.

''By 1944-45 the precarious supply situation of critical alloy materials facing Germany resulted in a program of intentional systematic reduction of nickel, tungsten and molybdenum in the composition of armor steel... Throughout the entire thickness range (the upper limits of which remained conformal with the ever increasing anti-armor calibers and shell types to a maximum of 250mm) first nickel-free and then low alloy steels were introduced in compliance with carefully determined heat treating methods in the smelting of this "standard" steel for all plants.'' [1]

''Improvisations by the German armor industry in the face of declining alloy content included multiple time quenching of plates in order to provide control over heat treatment, a process which must be conducted with care and precision to be successful. Times for immersing and removing steel from quench baths was specified to the second. Given the size and weight of plates such as the Panther glacis, inconsistency from one part of a plate to another would be a natural consequence. As alloy content dwindled, the margin for error in armor heat treatment narrowed.'' [2]

''As the war progressed, Germany was forced to curtail the use of certain critical alloys in the production of armour plate, such as nickel, tungsten, molybdenum, and manganese. The loss of these alloys resulted in substantially reduced impact resistance levels compared to earlier armour... The loss of molybdenum, and its replacement with other substitutes to maintain hardness, as well as a general loss of quality control, resulted in an increased brittleness in German armour plate, which developed a tendency to fracture when struck with a shell.'' [3]

The facts really do speak for themselves. They reveal that from 1944 onward, the Germans suffered shortages of alloying elements that forced them to use a different method of heat treatment for their armor plates. In theory, this interrupted quench technique would enable them to produce armor of the same quality as what they'd had before the crisis. But in practise, this technique was temperamental and finicky. Some mills were unable to maintain quality control, and churned out flawed armor as a result. This is what led to the armor of some German tanks suffering catastrophic failures in battle. It didn't affect all of the panzers made at that time, but it affected them frequently enough to be noticed by the Allys. And since this phenomenon only occurred in early 1944, TankArchives entire thesis is invalidated from the outset. His belief of German inferiority was a product of his own ignorance, bias, and poor research. But the story doesn't end here... There are still loose ends that remain to be tied up. Before this 'hypothesis' can be considered truly debunked, we will need to go one step further and look at the Soviet tests that he falsely cited as proof of substandard armor.

Tiger II destroyed by Russian

women with bazookas

Tiger II armor

TankArchives mentions a Soviet test involving the Tiger II tank, which was fired on by a variety of different weapons. He criticises how its armor held up. ''The front plates of the hull and turret, as demonstrated in the trials, are low quality. When the armour was not penetrated, the armour formed large cracks, and large fragments broke off the rear side.'' There are alot of problems with this statement. One issue is that the tests were conducted in November 1944. The temperatures on that day were -10 celsius, which may have adversely effected the ductility of the armor. Another issue is, of course, that the Soviets were only able to pierce the tanks glacis with the most powerful gun in their arsenal, the 122mm A-19 gun. And even then, it could only achieve penetations from 500 meters. The 100mm BS-3 gun only managed to penetrate when it hit weakened portions of the glacis, or the connections between the upper and lower front plates. The 152mm ML-20 gun didn't manage to penetrate the glacis at all, and some of the shells actually bounced off it! To be fair, the Tiger II did experience burst weld seams and spalling of the armor. But given the caliber of the shells being fired at it, this is hardly surprising.


Tiger I armor

TankArchives mentions a test involving the Tiger I tank, which was fired on by a variety of different weapons. He criticises how its armor held up. ''As a result of hits from 57, 85, and 122 mm guns, the armour cracks and fragments break off... The welding seams are very fragile, and are destroyed when the armour is hit by armour piercing shells.'' Again, there are alot of problems with this statement. One issue is that the Soviets were only able to pierce the tanks glacis with the 85mm S-53 and 122mm A-19 gun. The 85mm gun penetrated the armor from 1000 meters, but only caused cracks when it hear near the edge of the plate (and next to a previous shot). The 122mm gun penetrated the armor from 1500 meters, and caused cracks from the sheer force of impact. However, every other weapon that was fired against the tanks front armor failed. The 57mm Zis-2 gun didn't penetrate, and neither did the 76mm F-34 gun. Regular APBC and APHE shells failed, and so did the special HVAP ammunition! This was a very discouraging result for the Soviet testers. It revealed that the T-34 tanks main gun was completely helpless against the Tigers front armor... The issue of burst weld seams and spalling of the armor was less pronounced than in the Tiger II tests. There is no indication of brittleness in the plates.

Panzer III and Panzer IV armor

TankArchives mentions a test involving the Soviet 45mm anti-tank gun, which was used against three vehicles: The Stug III, the Panzer III, and the Panzer IV. He has no scorn for how the Stug IIIs armor performed, but is quite disparaging of the other two tanks. ''Then the PzIII is swapped in, and the performance is absolutely abysmal. Huge cracks from the same anaemic 45 mm peashooter, the front armour plate falls off, breaches up to 120 mm in size form... The PzIV doesn’t do much better.'' Lets take a look at the article in question and see whether he is giving an accurate description.

-The Panzer III being tested is an Ausf. H, which has 30mm applique armor on top of its 30mm base armor. Two shots against the front failed to penetrate, but do knock the applique armor loose.  Afterwards, more shots are fired against the turret and hull side. One of them penetrates the turret hatch, opening a crack in the armor. Two of them penetrate into the hull, striking near the turret platform and opening another crack in the armor. On its face, this seems to prove TankArchives assertion that the armor was brittle.

-The Panzer IV being tested is an Ausf. H, which has 20mm applique armor on top of its 30mm base armor. Three shots against the front fail to penetrate, but do open up cracks on the back side of the armor. Afterwards, more shots are fired against the turret side. Several penetrations are scored, but there is no cracking. Repeated hits knock the applique armor loose. Overall, these results seems to validate TankArchives belief that the the Panzer IVs armor wasn't much better than the Panzer III. But these are only first impressions!

In order to determine whether or not the plates were acting in a brittle or ductile manner, we need to know something about armor failure modes. This is a complicated subject that is also influenced by the type of projectile that strikes the armor. (In this instance, the 45mm anti-tank gun fired uncapped, blunt nosed shells) What will a deeper examination of these test results show?

First, lets look at the hits against the Panzer IV. The claim that cracking on the back face of the armor indicates brittleness is not true. What we're actually seeing is evidence of something called a star crack. These are associated with the initial stages of a ductile failure mode, either ductile hole growth or petaling. But in this incident, the 45mm shells ran out of energy before they could penetrate. This is not a sign that the Panzer IVs armor was brittle.

Next, lets look at the hits against the Panzer III. The claim that the front armor had fallen off is misleading, as this was merely the applique armor being knocked loose. And as for the cracking of the side armor, its interesting to note where these cracks occurred. The shells struck near stress points like the turret hatch and the turret platform. Hatchs are known to act as stress concentrators that allow cracks to propagate unimpeded for large distances. This is not a sign that the Panzer IIIs armor itself was brittle.

Holes in a metal plate act 

as a stress concentrator

Quotes from Heinz Guderian

In a final bid to solidify his theory, TankArchives attempts to show his readers that German armor was running into quality problems even in late 1941. He provides a quote from Heinz Guderians book to prove this: ''Frontline officers suggested that we should build tanks exactly like the T-34 in order to correct the unpleasant position of our armoured forces, but this position did not receive support from the engineers... Additionally, our hardened steel, whose quality was dropping due to a lack of natural resources, was inferior to the Russians' hardened steel.'' That almost sounds convincing... However, its important to keep in mind that this quote comes from a Russian translation of the book.

In the German and English translation of his book, Guderian didn't say anything about the quality of German armor deteriorating. What he actually says is this: ''The officers at the front were of the opinion that the T34 should simply be copied, since this would be the quickest way to put to rights the most unhappy situation of the German panzer troop: but the designers could not agree to this... Also, as far as steel alloys went, we were at a disadvantage compared to the Russians owing to our shortage of raw materials.'' [4] In his own words, therefore, Guderian believed that resource shortages made it impractical to copy the armor composition of the T-34 tank.

So really, his comment has nothing to do with the 'inferiority' of German armor. Guderians concern lay with the perceived superiority of Soviet armor. The T-34 tank used an MZ-2 steel alloyed with lots of rare elements, which was only practical because of all the USSRs natural resources. At the time, the Germans were quite envious of this type of armor. MZ-2 steel could be heat treated to very high hardness levels without a loss of toughness. [5] This gave it the ability to shatter the uncapped Pzgr shells that were used in 1941, thus rendering excellent protection. However, this situation quickly changed after the Germans introduced the improved Pzgr 39 shell. This was a capped projectile with a hardened nose, which could easily penetrate the high hardness armor of the T-34. This type of plate was so ineffective against Pzgr 39, in fact, that it provided less protection than rolled homogenous armor. In retrospect, it can be seen that the Soviets relied on an innovation that quickly became obsolete.



Sources

[1] The Panther & Its Variants, by Walter Spielburger. (Page 82)

[2] World War II Ballistics: Armor and Gunnery, by Robert D. Livingston. (Page 8)

[3] Eastern Front: Encirclement and Escape by German Forces, by Bob Carruthers.

[4] Panzer Leader, by Heinz Guderian.

[5] WAL Report: Review of Soviet Ordnance Metallurgy. (Page 4-5)

World war 2 tank armor

Introduction

This article will give a brief overview of the types of armor plate used on tanks during WW2, and examine some of the different ways it could fail when struck by an armor piercing shell. Different types of projectiles can cause the same plate to fail in different ways, so we'll also need to go into detail about that. Then we'll go over the importance of thickness/diameter ratios, how they influence the effect of armor sloping, and how shell normalisation actually works. Finally, we'll look at manufacturing defects that can compromise the quality of an armor plate. The field of armor and ballistics is complicated, but not so much that a basic understanding can't be gleaned.


Types of tank armor

Generally, there are two different types of armor that were used on tanks and AFVs during WW2. The first type of steel armor was heated until the point it was red hot, and was then forged into the required shape. This is rolled homogeneous armor. The second type of steel armor was heated until the point it melted, and was then poured into the required shape. This is cast armor. Both types of armor had to be heat treated and tempered until they gained the desired metallurgical propertys, such as tensile strength, hardness, etc. The alloying elements introduced into the steel -such as manganese, tungsten, nickel, chrome, vanadium- would influence its final form. Rolled homogeneous armor (RHA) had a uniform level of hardness throughout the plate, usually about 250-350 BHN, depending on how thick it is. Face hardened armor (FHA) had two different hardness levels in the plate: The surface was about 450-650 BHN, while the rest was about 250-350 BHN.

FHA is useful against projectiles with a diameter smaller than the plate thickness, I.E., an undermatching shell. It also has the ability to shatter uncapped projectiles and defeat them. However, FHA has the disadvantage that it is more prone to cracking, which gives it lower multi hit protection than RHA. Moreover, FHA plates offers inferior protection to an equivalent RHA plate when hit by capped shells. Another type of tank armor is the so called high-hardness armor. This is similar to FHA, except the hardening extends through the entire depth of the plate, and not just the surface of it. It has a uniformly high level of hardness throughout the plate. For the most part, only the Soviet Union used this type of armor during the war. It had the same strengths and weakness' as FHA did, but taken to the extreme. High hardness armor was only useful against undermatching or uncapped shells. Interestingly enough, cast armor could also be heat treated to achieve the same levels of hardness.


Modes of armor failure

What are some of the different ways that armor plate can fail? The first thing to keep in mind is the difference between penetration vs perforation. When a shell perforates, it passes completely through the armor plate and flys into the vehicle itself. When a shell merely penetrates, however, it does not pass through the plate: It produces a crater and knocks off pieces from the back side of the plate. This effect is known as scabbing or spalling. This is a less serious mode of failure.

In instances when a shell actually perforates the armor, you have to distinguish between ductile and brittle modes of failure. This is absolutely essential. Brittle failures are more dangerous than ductile failures. We'll detail some of the different categorys below. Please note, however, that the type of projectile which strikes an armor plate will strongly influence the manner in which it fails. A shell with an armor piercing cap will usually cause ductile failures in the plate, while uncapped shells will usually cause brittle failures in the plate.

-For ductile failures, there are three different categorys. Plugging, ductile hole growth, and petaling. Ductile hole growth is when the plate (at the impact site) is holed from front to back. Petaling is when the back of the plate folds out. Plugging is when the back of the plate is ejected into the vehicle, along with the projectile.

-For brittle failures, there are two different categorys: Brittle fractures, and brittle plugging. Brittle fractures is when the plate (at the impact site) is shattered from front to back. Brittle plugging is when the back of the plate is shattered and ejected into the vehicle, along with the projectile.

Note: With ductile types of plugging, the shell is still intact and exhibits little or no change of shape. With brittle plugging, the shell is not intact and exhibits a major change of shape. The size of the plugs knocked off the backside of the armor are also larger.

Modes of armor failure

Types of armor piercing shells

There are a few different types of projectile designs, which have different advantages and disadvantages. There is the standard armor piercing (AP) shell. And the armor piercing capped (APC) shell. This is an AP projectile fitted with a cap that prevents it from shattering. There is also armor piercing ballistic capped (APBC). This is an AP shell fitted with an aerodynamic windscreen to improve its ballistic coefficient, but does not prevent it from shattering. Then there is an AP shell fitted with both types of caps (APCBC). This not only enhances its ballistic coefficient but also prevents it from shattering.

Note that most of these designs have a tiny cavity at their base, which is filled with explosive. This works to burst the shell behind the armor plate, increasing the damage it does. The other type of shell is armor piercing high explosive (APHE). This is a regular AP shell, but with a larger explosive filling. Then there is armor piercing composite rigid (APCR). These types of projectiles have a dense tungsten core and an aluminum body. They have excellent penetration, but poor aerodynamics.

As a general rule, projectiles without an armor piercing cap tend to defeat armor through brittle fractures and brittle plugging. When they do succeed in punching through an armor plate, they leave jagged holes wider than the caliber of the shell. Projectiles with an armor piercing cap tend to defeat armor through ductile hole growth, petaling, or plugging. When they punch through an armor plate, they leave neat holes that are the same width as the shells caliber. Keep in mind that these distinctions are not absolute, and there are instances when capped and uncapped shells can defeat armor in different ways than this.

Its also important to note that the nose shape of the projectile can also have an influence on how it interacts with the target plate. Blunt nosed projectiles have an increased tendency towards plugging (of both the brittle and ductile variety). Sharp nosed projectiles have an increased tendency towards petaling and ductile hole growth. [1] The difference in nose shape also influences their effect on unsloped vs sloped armor. Blunt nosed projectiles are superior against sloped armor plates, whereas sharp nosed projectiles are superior against unsloped armor plates.

Types of armor piercing shells

T/D ratio and sloping

Failure mechanisms for armor are largely dictated by the T/D ratio, where T is the armor thickness and D is projectile diameter. (Simply divide the former by the latter) The T/D ratio dictates that the more the thickness of the armor plate exceeds the diameter of the projectile, the harder it is for the incoming shell to achieve a penetration. The converse is also true of course, and the more the diameter of the projectile exceeds the thickness of the plate, the easier it is for the shell to achieve penetration. To put it simply, larger shells have an advantage over relatively thinner plates. Whats more interesting is that T/D ratio can also determine whether or not the degree of sloping in an armor plate is effective or not.

One way to demonstrate this is by looking at the hull front of a Sherman tank. Early models had a 51mm thick glacis sloped at 56 degrees, for an LOS thickness of 91mm. Later models had a 63mm thick glacis sloped at 47 degrees, for an LOS thickness of 92mm. Even though there was practically no difference in either plates line of sight (LOS) thickness, the later model of Sherman actually offered superior resistance. Because of the more favorable T/D ratio, they had a higher chance of withstanding hits from 75mm APCBC projectiles. The 51mm thick glacis was equal to 98mm of RHA, while the 63mm thick glacis was equal to 118mm of RHA. (Assuming there were no flaws in the armor itself) [2]

Another important phenomenon to understand is shell normalisation. There is a popular misconception that when a shell hits an inclined armor plate, it will turn by a few degrees before digging into the armor, thus reducing the acute angle it has to negotiate. Such that a 50 degree slope becomes a more manageable 45 degree slope, or some other such reduction. In fact, this is not what actually happens. Normalisation only occurs after the shell has dug into the armor, not before. So when a projectile hits an inclined armor plate, the net result is that it ends up making an S-shaped hole. The difference in the angle of the entrance and exit hole is what leads people to believe that 'normalisation' has taken place.

This is not how normalisation works!

Manufacturing defects

The last factor we'll examine are manufacturing defects that occur at the mill where armor plates are heat treated and tempered at. These mechanical flaws in the structure of the armor will reduce its resistance to impacting projectiles, sometimes by a small amount, sometimes by a severe amount. There are a number of different factors that can lead to substandard armor plate being produced. Early in the war, the U.S. experienced problems with manufacturing defects. The Sherman tank made extensive use of cast armor, not only in the turret but in the hull as well. These armor castings frequently suffered from hot tears and shrinkage cracks. [3] RHA plates were not without problems either, and were sometimes found to be riddled with stringers and laminations. These problems stemmed mainly from the huge expansion of the U.S. tank industry, which went from producing over 300 tanks in 1940, to over 23,000 tanks in 1942. The sheer quantity of armor plate required meant a decline in quality control.

Later in the war, the Germans also had their fare share of trouble with manufacturing defects. By early 1944, they were suffering from a shortage of alloying elements like nickel, tungsten, molybdenum, and manganese. This forced them to reduce the quantitys of these critical alloys, or to find substitute alloys. In order to ensure that their armor plates did not suffer from brittleness or flaws, a different method of heat treatment also had to be utilised. The Germans eventually settled on the so-called interrupted quench process. [4] This required great precision in the tempering of the plate, and if the timing was not within a certain margin, the plate would be mechanically flawed. It was not always possible to detect armor with defects. The steel mills were unable to achieve consistent quality control, and were unintentionally churning out many flawed plates.

The Soviet Union experienced some notable problems with manufacturing defects, as well. These issues weren't as ubiquitous as those plaguing the Sherman tanks, but they still cropped up relatively often. The Americans noted their presence in a number of different metallurgical reports. Some of these difficultys can be linked to the fact that much of the USSRs industry had to be hastily evacuated to the Urals in 1941, in order to avoid being captured by the invading German army. The rest can be linked to the fact that Russia was technologically less advanced than the other great powers. Armor castings (especially on the KV-1 tank) tended to have issues with hot tears and shrinkage cracks. RHA plates were sometimes not adequately cross-rolled, and were incompletely quench hardened. [5] This resulted in uneven hardness levels in an armor plate, an undesirable feature. The high hardness armor of the T-34 was noted for its tendency to create spall.


Sources

[1] World War II Ballistics: Armor and Gunnery, by Robert D. Livingston. (Page 15 and 16)

[2] World War II Ballistics: Armor and Gunnery, by Robert D. Livingston. (Page 28)

[3] World War II Ballistics: Armor and Gunnery, by Robert D. Livingston. (Page 6 and 7)

[4] World War II Ballistics: Armor and Gunnery, by Robert D. Livingston. (Page 8 and 9)

[5] Metallurgical Examination of Armor and Weld Joint Samples from Russian Medium Tank T-34 and Heavy Tank KV-1. (Page 1 and 9)