Denizen

As for the information presented in the drawings on battlefield.ru the following must be said: The drawings are not works of the people behind that website, however the numbers on them, are. Several of those exact drawings appear in their original form in some of the Russian books I used as sources for this debate, however, the numbers represented on them in the books are different. IF you look closy at the armor profile of the IS-2, you will see two different fonts used on the numbers. The italisized numbers are those in the book, the others are not. Incidentally, the book which has the IS-2 profile uses it to represent *every* model of the IS-2, I have yet to see a version-specific diagram of the entire tank. The writing on that site is genrally quite accurate, but the diagrams they present often aren't worth the bandwidth they use up. [ August 09, 2003, 05:13 AM: Message edited by: Denizen ]

Yes and no; it all depends on where the weight of the gun is balanced. The weight of the mantlet is not carried by the front of the turret in the same manner as the turret armor itself, rather the mantlet's weight is genrally balaced as part of the gun with which it moves. *If* the fulcrum of the gun is futher back into the turret than the front face of the turret itself, an increase in mantlet weight will affect the whole turret balance less than than the same weight increase of armor on the turret front. Granted, it will affect the balance of the gun, but this can be counteracted by the weight and shape of the interior gun assmebly. Thus it is not necessarily true to say an increase in mantlet weight and turret weight are one in the same in terms of balance. In other words, the gun acts as a lever inside the turret, and as the mantlet rests on the gun, it is part of that lever. The impact of more total weight on the level will only affect the turret balance at the fulcrum on the lever. So if the fulcrum moves back, the overweight balance on the front of the turret is relieved at least partially, and adding a bit more weight to the lever at the mantlet and a balanced amount on the inside might only bring the complete turret balance up it is former figure, even though the mantlet is now heavier. There is, furthermore, evidence that a movement of the fulcrum to the furthest rear position perimissable may have taken place. The visible weld seam that connects the main turret assembly to the gun mounting moved backward when the change was made to the wide mantlet, even thougth the turret front extened out as far as in the early version. [ August 09, 2003, 04:32 AM: Message edited by: Denizen ]

For purposes of clarity I will rewrite my argument: Ballistic protection between the early and late variants of the IS-2 differed significantly, not only relating to the redesigned hull but to the turret and mantlet as well. The early desgin suffered a number of flaws do to the pace at which the program developed. Not unlike the earliest Panther, the early IS-2 suffered from a variety of protective failures, ranging from the flattened front face of 'curved' turret armor, the un-reinforced mantlet installation which brought about breakages of the mantlet from the turret itself when hit, as well as the various problems of vertical hull plates creating shot traps vulnerable spots. However, what few people seem to realize, is that just like the Panther, or better yet the Sherman, the IS-2 saw its flaws removed througth development based on combat experience. Comparing the early IS-2 and the late IS-2 is a comparision along the lines of the first M4 and the last of the 'easy-eights', meaning that the changes were so significant that the result could hardly be seen as the same vehicle. Indeed by the time the IS-3 finally became availible, the IS-2 had progressed to such a point that the IS-3 was almost redundant. Aside from introducing the frying-pan turret, the IS-3 has no claim to fame. I am first and foremost a historian at heart, and frankly I find it disheartening that most of what the west is recording in histories when it comes to military engineering is the contemporay picture of what we knew when it happened. We need look no further than the fact that a game showcasing the war that cost more lives to Russia than any nation has ever lost in history (excepting native Americans) uses predominantly German source material. True, a few voices have brought about interesting realizations from the east, but this branch of histroy is fading away faster than it is correcting itself. I don't claim to have answers from everything, but in the case of the IS-2 I think history has allowed the significance of an engineering feat to fade into history. The way I see it, the akward child of the KV grew into one of the most capable designs of its time. It had more explosive firepower than a tiger, at the weight of a Pather, with the speed of a Sherman, and the complexity of a panzer IV. Hopefully we can find an answer to whether it had the protection of a tiger, or a tiger II. Moving on, I will take a shot in the dark and ask; does anyone know of the existance of scematics of the particular parts making up the IS-2 mantlet and its connection to the turret? More and more it seems as though all we have to go on for armor thickness is conjecture. Might anyone have any idea where the 100mm mantlet figure came from? Usually armor measurements are lsited as maxiumums, so it seems odd that a german photograph showing 110mm could be the same piece of metal even tanking into account manufacturing techniques. Furthermore does anyone have a armor measurement that is proven to be taken from a late model IS-2? If the late model never made it into western hands, how can we trust old figures? Published data before the cold war ended indicated 100mm largley, and not Zaloga's 160mm which I am inclined to believe he measured, after all I am fairly certain he was the first westerner to discover the mystery KV tank from the finnish army museum. That KV incidentally brings up another issue, the infamous KV-1 that the Germans designated "c" but which has since fallen into the vaccuum of history only to be resurrected by Zaloga's writing. [and photos] I do not think it impossible for details of the last variant of a quickly replaced series to have been erroneously covered by history, but it would seem that some on this board do not share that view. :confused: Possibly I spend to much time looking at pictures! [ August 08, 2003, 12:54 AM: Message edited by: Denizen ]

The debate is reminding me of the T-64/T-72 debacle back in the seventies, for a while even Jane's thought they were the same tank because they looked so similar. To this day enthusiast-level publications still see the T-72 as the T-64 replacement. The devil is in the details; if the stalist russia had made more of an effort differentiate the nomenclature of its desgins there would have been a tank called IS-2.5

Perhaps I have been caught up in semantics, but are you implying that the British never had a late model to measure either? Where then do the western estimates of the late IS-2 come from?

This is really what I have been looking for all along, and as far as I can tell this information does not exist. The simple fact is that not all curved armor had the has the same ratio between thickest/thinnest parts. Similar, but not the same. If you look carefully at photos you will see that the early turret has a broad curved surface on the front end, while the late turret has a visible 'snout' such that the vertical distance between the driver's periscope and the bottom of the turret changes by 15 cm or so, and a simlar thing happens on the top of the turret. It would also appear that the mounting of the gun was moved back into the turret several centimeters as well. The front excesses were effectively shaved off. Together these factors would have had an impact on the cg. Its a subtle change on the outside, one which many a moddler has overlooked, but given the massive weights involved, even a reltively small change in distance could put it back into balance For the glacis there are fewer clues, certainly 100mm would have been enough at that angle, but I suspect the designers may have been reluctant to reduce the overall thickness from the previous hull design out of the fear of not being ready for the 'next threat'. Additionally, given the fact that the post war moderniztion program did not involve replacing the glacis, I have to wonder if the IS-2 would have seen almost three decades of service if its armor was no better (or worse) than the T-54, to say nothing of the later heavies. Even though I am well aware that russian equipment was built to be in service until or even after reaching obsolesence, you have to wonder how the IS-2 outlived it sucessor(s) (thougth lets not talk about the IS-3 in this thread) PS Lorrin I have read your book; you don't need to rewrite it in this thread. [ August 07, 2003, 11:21 PM: Message edited by: Denizen ]

Amdeo: As I mentioned previously, even Russian sources disagree on the thickness of the late model glacis plate, after looking through my books I have found the same 100mm cast hull and 90mm rolled hull, however, the Encyclopedia Tankob disagrees. http://www.armybook.com/summary.html?code=0103008105 While I usually never trust a single source for anything, when books disagree it is only logical to believe the more comprehensive work. As the owner of approximately 150 books directly covering armor, Encyclopedia Tankob is in my opinion, the Jane's of historical armor. With a bibliography that has as many words as some armor books do in their entirety, and an endorsement by a Russian historical society (if that makes any differance to you) this is the source i trust most. It gives a 120mm figure for the hull armor and 160 for the thickest part of the turret. Short of having the blueprint in hand, it won't get any more accurate than that. Unless of course, you are lucky enough to get vacation time. As a sidenote I would like to mention that book has some information on western tanks that is supposedly classified this side of the ocean

rexford: you are correct that RBF does state that the turret had balance problems, however as I mentioned in the first post, the same webpage says just a few lines down that the movement of the gunsight created a new turret complete with armor improvements. Thus the weight problem was only a temporary issue for the *early* variants. The new turret had an enitrely redesigned front, include changes in the cg such that more weight on the front *was* possible. Without the weight argument to resort to then, we can only look at the german/british measurements of the tanks, but if you take another look at the photo from yahoo tankers, you will see it is an *early* variant, thus the thickness of the *early* mantlet was roughly the 110mm figure painted on it by the germans. Could the discrepancy with the British figures then have something to do with measurements coming from both an early and a late tank? With the weight problem resolved, and the necessity of designing another mantlet for the gunsight, it only seems logical that the armor improvements were included as well, as indicated by RBF and the book i mentioned ealier. Oh, and thanks for responding, now we can have a real debate. [ August 07, 2003, 08:22 PM: Message edited by: Denizen ]

First of all, thanks for all of the attention! I will read some more to sort some more of this out tonight, but for the moment I have a few comments: Amedeo: I ran across a reference that that a new turret assembly for the IS-1/IS-85 that mentioned a new assembly to mount the 100mm naval gun as used in the SU-100 but rejected due to its excessive size/weight (different center of gravity than 122mm) Are you certain that the linked refernce is reffering to a change rejected *after* march 1944? We know from pictures that the assembly of the mantlet and indeed the majority of the turret went through a significant change during this period. If the 130mm matlet for the IS-2 was rejected, what were the specifics of the new mantlet they created? I had assumed from photographic evidence that they came up with a whole new turret able to fit the 130mm mantlet, discarding the interim IS-1 turret, just as they came up with a new front hull. As for the thickness of the glacis plate, I avoided quoting a figure ealier beacuse even my Russain sources are in disagreement... I'm looking into this further now

Tero: The early turret mantlet was horizontally narrow, but it extened from the top of the turret to the bottom. Given its lesser thickness, the area of the early mantlet under the gun was certainly a weak spot. While you mentioned 'reports', there are in fact photographs of early IS-2 tanks knocked out, with the whole of the manlet having separaed itself from the turret. The rebuilt mantlet corrected this problem. As for the "drivers vision port", you will note that the tank in its earliest versions (ie IS-1) had a stepped front hull like the KV. While the glacis was sloped, the part of the front hull with the driver's vision port was *vertical*. This error was corrected in the IS-2 from the beginning of 1944 onwards. The new front hull, completely sloped had a vision port flush with the hull surface itself and a protective 'lip' of armor to boot. While the vision port area was a vulnerability in the earlier version, the bulk of the IS-2s were built with vision ports proven to survive nearly every foreign projectile. As for the turret ring, yes the IS-2 was vulnerable if it was hit there, but so was every other tank. The downward curve on the mantlet could have sent projectiles into a vulnerable area at the ring, but changes in frontal protection meant the later versions had as much armor at the ring as any other place on the tank. Having looked at dozens of photos of knock out IS-2s I have only seen serious turret ring damage on the earlier versions, the late version were usually only destroyed by hits to the side of the tank, or of course by bombs. [ August 07, 2003, 02:06 PM: Message edited by: Denizen ]

Sparked by the suprising vulnerabilty of the IS-2 turret front in CMBB, several months ago I set out to research the tank in more detail, in part to find out how its designers could have justified an obvious design flaw in the IS-2 armor protection. We have all seen how well the glacis of the IS-2 resists some of the most powerful shots in CMBB, only to be decidiedly unimpressed by its turret protecion; how could the red army have accepted such an oddity? Limited by the few western publications availible on the IS-2, I found only confusion. Some, like the decades old Russian Tanks by John Milsom, agreed with the BFC take on the IS-2 turret armor thickness, while others, notably Zaloga's Red army handbook gave a wild turret armor figure some 60mm in excess of the data BFC used; 160mm turret front. When I brought this up on the board months ago, I was told that even the experts like Zaloga make mistakes on these things. Well, I certainly could believe that given the errors I had seen made by other 'experts' notably Ian Hogg who in the Greenhill AFV "Data Book" confuses the IS-2 with the IS-3, saying both entered production in 1945 Knowing that the data in such books could be flawed, I studied the availible pictures carefully and noticed something that would turn out to be important. The Differences between the IS-2 models produced at the very end of 1943/very early 1944 and those produced once production escalated in mid 1944 were not limited to the hull. As many will know the early IS-2 variants had the stepped front hull similar to that of the KV, but a close examination will reveal large differences in the turret as well. All of the earlier tanks a narrow mantlet with the gunsight hole on the gunners left and the mg hole on the gunner's right, the two holes being roughly equidistant from the gun itself. However the later tanks had a mantlet that streched to the gunner's left a considerable distance, the sight being on the far left side and the mg on the gunner's right, the sight being a considerble distance from the main armament. This pictoral evidence was enough to show that not only did two different mantlets exist, but the differnce between them was great enough to have changed the internal layout of the turret itself. This led me to believe that rather than being a simple difference in manufacturing technique, there was a change in the tank design that required replacement of the old mantlet. Here however, I ran out of information. Despite the obvious visual difference in the tank, no book I could find even mentioned the existance of more than one mantlet design. I thought about it for a while and came up with the possiblility that maybe the Zaloga turret armor measurement and the Milsom measurement were in facgt measurements of two differnt mantlets. I brought this up on the board some time ago, but it was quickly dimissed by the mention that the curved nature of the mantlet meant that different parts could have differt thinknesses, zaloga picking the small thick part while the Milsom measurement was the majority of the area. This made sense certainly, but it did not explain why the factories went through the pain of significantly changing the mantlet in the first place. Certainly there had to have been some sort of problem with the ealier desgin, but what was it? Playing CMBB it certainly seemed logical for them to have up-armored the mantlet, but this was purely conjecture. Since the later mantlet was visibly larger, it seemed reasonable to rule out the early one from being too difficult to build, so that the raeson for the change would have to be related to battlefield performance. Perhaps the sight was too close to the gun on the early mantlet? This possibility was quickly ruled out (foolishly as it turns out) upon discovering that the T-34 sight was just as close, and countless variations of T-34 had progessed without any movement of the mg. So I came to the conclusion that the mantlet design had to be changed due to weaknesses in protection. Unfortunatley, I had no proof. Living several thousand miles from the nearest IS-2 there was no way to examine it in person. I did however find some hope. On the now well-known baattlefield.ru site, the IS-2 section had a breief mention of the mantlet change, the first I had seen, and furthermore this statement was made: "Statrting in May 1944 a new turret with widened porthole was manufactured, which resulted in the sight being moved to the left. The armor protection of the tank's mantlet was improved and the armor thickness of the sides of the lower hull was increased. Well, I was wrong about the gunsight, but here I finally had information that the the larger late mantlet was indeed thicker than the small one in the early tanks. I got to this stage a few months ago, but then I had to face the inevitable question; how much thicker. Obviously the dozens of books I in my collection had no answer to this question, and neither as it turned out, did battlefield.ru. So then where was I to turn? I scoured the internet and local libraries for any information at all, again, only to find that if the answer was out there it had to be in Russian. So I order a few books in russian, from armybook.com. However, not knowing a word of Russian I knew I was up for a challege. Once my books arrived I began to translate them at a snail's pace for that magical sentace I knew would be there somewhere. And, at long last I've found it! Proof can be found in 'IS tanks' a special issue of the journal Tankomaster, page 55. Here is a literal translation of the sentance, using the Random House Russian English dictionary: "By protection alteration part turret armor increased to 130mm that factor increased more greater" This then means that the base thickness of the late turret was 130mm, and perhaps the thickest parts were more, to explain Zaloga's measurement. It took sweat, tears, and a lot of time but I think I have finally sorted this issue out. The later turret design/mantlet is at least 130mm thickness, far apart of the 100mm thickenss of the earlier one. CMBB uses a 100mm value for both, and given the attention to CMAK now, that egreigious error will likely stay in CMBB forever. Oh well; but please pass the word on, I don't want to know I wasted all those hours translating russian for nothing. [ August 07, 2003, 03:14 AM: Message edited by: Denizen ]

I agree as well... The Tiger was given a unique trait "reinforced turret armor" which gives it an odd advantage in terms of armor protection, as there were reinforced areas of the IS-2 turret in real life, up to 160mm on the late version mantlet (the early mantlet only went up to 110mm) Dont expect BFC to do anything about it though.

The IS-2 has had perhaps the largest amount of conflicting information written about it than any other vehicle of its day. I find it interesting that Steve uses Zaloga's views of IS-2 use but the game does not use Zaloga's data on the IS-2. I don't think that BFC will ultimately be able to resolve this issue by argument or action, more likley it will take some more scholarly study of the history of the vehicle before the situation is resolved. After all, there is still disagreement over the number of machine guns carried on the IS-2! [ December 02, 2002, 02:47 PM: Message edited by: Denizen ]

speaking of the IS-2, it is missing an mg as well; BFC still wont admit the IS-2 had a bow mg.

bump