The substance of this counterfactual is pretty simple. If I adopt one simple rule: that the BEF is equipped with standard 1945-era equipment and tables of organisation, I get to replace the 50th (Northumbrian) Division, the only designated mobile division in the BEF in 1940, with the only kind of mobile division that existed in the British army in 1945, which is to say, an armoured divisions.
Let the BEF's march to contact on 10/11 May be led by four regiments of these, and it is hard to imagine Army Group B not being in a world of hurt. I wouldn't want to overstate the likely influence of a single armoured division, but there is simply no way that the Germans could win an encounter battle with a force of effectively invincible tanks.
|Hugely fun series of "walkaround" videos of the Comet|
What would have happened next is left to the imagination of the reader, but had I been in Bock's place, I would have pulled Army Group B back to the West Wall, exposing the flank of Army Group A and ending the offensive in the west.*
This counterfactual is an answer to Correlli Barnett, of course, all of thirty years, less one month, late. (Which makes Audit of War a "beach read." Time to set the scene!)
To this you may object that this is a pretty anodyne counterfactual. Perhaps I could punch it up with a protagonist who finds time out from designing future tanks to introduce double-entry bookkeeping, journalism and cheap brandy?
|Who else learned the history of the Gothic Wars from this?|
So Correlli Barnett publishes Audit of War, a book that fascinated me, persuaded me, and changed my life, and the lives of many others, if it is true that it was Margaret Thatcher's favourite book, which it probably wasn't, because it didn't have to be, because as it turns out, Thatcher and Barnett had been soaking in the same marinade for their entire lives.
I also didn't like it, perhaps why I reacted so strongly to it, and why Steve Straker was so indulgent of my obsession. It wasn't until many years later that I realised why.
I posted a "song of the summer of 1986" above, quite intentionally choosing one not yet released in the first week of July. I have a reason for that, although not one I can articulate. It's not quite that it's the one I like most, or that it's the most consequential. Look, here's the list, you go see what you make of it. This is what makes history a tough business. All of history has happened. You're in dialogue with every bit of it, even though you've only given clear thought to a bit of it. I am not going to reject the idea of a universal history, because, without it, you can't expect to make sense of the past, but I do have to say that it is a very dangerous undertaking, as Barnett illustrates. The power behind Audit of War is that it was a book about everything. Barnett has a hot take about everything from coal mining to Nineteenth Century public education. In retrospect, this should have been a big, blinking stoplight. Not to put to fine a point on it, but Barnett had a sweeping theory of technology, a contrarian's negative view of the society in which he lived, and a decades-long collection of press clippings that conformed to his thesis.
The press clippings are the hardest part. You want to say something mean about the Supermarine Spitfire? Drop a line about how it would have had a better performance had it been equipped with four American .50 Browning machine guns, like the Mustang, instead of eight .303s, like Ralph Sorley wanted. American! .50! Mustang! Ralph! Bam! Drop the mike!
Repeat for auto engines, continuous strip mills, coal tar refining and shipyard fastening practice, and you have what looks like an unchallengeable edifice. Consider the exhausting journey of disentangling the .50 cal story. I am lucky enough to be lead to one of H. R. Allen's goofy books, stumble on Arthur Harris' very personal relationship with Rose Brothers, and, finally, doing the very hard work of actually reading myself into mid-century aviation technology, discover in Aviation the desperate and false argument that the American bombers being shot down in unescorted missions over Germany really were so shooting down that many German fighters because .50 cal is so awesome.
This is a lot of work, and even now I cannot put my finger on the evidence that once led me to suspect a conflict of interest in regards to Harris and Rose Brothers. Looking back on that adventure would be more than enough to discourage anyone from pursuing the question of, say, continuous strip mills.
On the other hand, at some point you read the long, wonderful technical chapters at the back of pre WWI numbers of Brassey's Naval Annual, discover the entire meat of Barnett's Jutland technical critique being dismantled and exposed as products of Tirpitz's propaganda machine, spun to excuse the demoralising effect of the revelation that the Kaiser class would repeat 12" guns. And you say, "we know these Pappenheimrs," and are not surprised when it finally does come time to learn about the history of the continuous strip mill in England.
At this point, you are led to the world-weary pose of discovering the long dead theorist who has an apparently purely empirical Barnett in his grip. (I would say, "practical man," but that is an insult in Barnett's world.) It turns out that Barnett's worldview has an intellectual pedigree that goes back to the response of the British establishment to the forced union, or "coordination" of the various Prussian state churches by Frederick William III in 1817. British church people looked at this exercise, imagined its equivalent in Britain; and either recoiled from it or embraced it. And if you were in favour, you conjured up various consequences, particularly in education. Church reform is far from the only reason for the British Nineteenth Century interest in German thought, but you can see the way it influences Barnett in the review above. Honestly, who else now can even hold still and keep a straight face for arguments about how the Evangelical wing of the Church of England broke science in late Nineteenth Century Britain?
Barnett, however, is not on about theology. He's more concerned with. . .
That's probably not the most enlightening version of a concept that I am most familiar with from the late 1970s GDW roleplaying game, Traveller, but it does have the advantage that it is not nearly as complicated as the current official one, which you will find here, where you will learn that in the course of the Twentieth Century, the Earth has passed from Tech Level 5 to . . Tech Level 8? Let's see, we've got your flat screens and video telephones, and apparently our "improved batteries" are pretty improved, and whatever "early fusion" might be, we probably have it. And "Arcologies" are just really big apartment buildings, right? It's the "orbital cities" that don't really seem to fit. Anyway, it seems pretty clear that we moved from Tech Level 5 to Tech Level 6 in WWII. Or some of us did, since there's that pesky Third World.
So, given that, say, the Congo wasn't at Tech Level 5 in 1939, what's stopping Britain from being Tech Level 6 in 1940, and unleasing a swarm of Comet tanks on those poor Germans? Bishop Wilberforce, that's who!
This is the part where I don't make fun of Marc Miller and the lads at GDW: "Tech levels" are meant to be descriptive, and not a theory of history. The "black books" of the original Traveller set certainly don't explain how a society ratchets its way up from Tech Level to Tech Level. They don't even tell us what happened to the Free Trader Beowulf. The problem is that we have tended to take description as prescription. It would be nice if Earth hit Tech Level 9 sometime soon. Commercial fusion power (not to mention "early" antigravity) would really, really help us out. The issue here, I suggest, is that what we're doing right now is waiting for Tech Level 9.
We are waiting so hard, guys, and this is the part where some drilling down might help. Did we really get from Tech Level 6 to Tech Level 6 by waiting hard?
Here's a tank of 1918. That's your Tech Level 5, presumably. Sure looks 5ish.
And here's a tank of 1945. Tech level 6! (If not 7.)
|CC BY-SA 3.0, https://commons.wikimedia.org/w/index.php?curid=285856|
Actually, I'm not sure I don't remember 1986 better than I remember 2007.
So the question is: how did the Comet get that way? Here's a table with weird sizing thanks to the cutting-and-pasting from Word. You'll notice that I've left off the guns, since the only real anomaly here is the tiny (by muzzle energy) weapon foisted on the Sherman, basically the same gun, ballistically speaking, as carried by the T-34, which gives up well over 10% of the weight. The Comet was designed, on the basis of prewar theorising, as a "heavy cruiser," capable of undertaking both the exploitation mission of the "cruiser" and some of the assault role of the "infantry tank."
Cruiser Tank Mk IV
30mm (not specified)
50mm (glacis –hull)
110mm (turret, AusfA)
*Tank experts love to cite "effective armour" rather than the actual thicknesses. They have a point, in that the actual penetration characteristics of a piece of armour depend heavily on the expected angle of incidence of the shell. Since the default assumption for tanks is a point-blank, near level impact, the actual penetration resistance is a straighforward multiplication of the tangent of the slope angle with the actual thickness. I don't think that the quantum chemistry quite holds up, but this is an accurate first approximation, for all that I know. The problem with citing "effective" armour is that it isn't very helpful from an engineering point of view, where we need to know the weight of the piece and its manufacturing characteristics, and the overall shape of the tank is deducible from the dimensions and weight. (The lower it is for its weight, the more pyramidical it is, and the designers would have to be very dumb indeed not to file down the corners at the front.)
So some comparisons are in order. The Cruiser Mk IV, an actual British cruiser tank available in 1940, has a good turn of speed, but not much armour. This is because it is not a "heavy" cruiser. For that, you can compare it most directly to the French Somua S35, which is still not that impressive from an armour point of view, but is certainly a huge improvement on the MkIV. It also has a 47mm antitank gun, roughly baliistically equivalent to the Mk IV's 2 pounder (40mm), but firing a more useful explosive round. Not that a three pound shell is much of an improvemen ton a 2lb. The strangeness of the Somua design, as well as the limits on armour thickness, reflect the French specification's succesful resistriction to just under 20t.
As for the 20t weight limit, General Martel has a lapidary explanation: most rivers in western Europe are canalised. A tank can hardly ford a wide concrete ditch, and so bridges must be thrown across them at locks. Existing modular field bridges have a weight limit of 20 tons. Ergo. . . This also works as an explanation for why the Russian General Staff would throw over the 20t limit, albeit not without putting in place a new limit that would prevent the designers for opting for "all the weight." They also specify engine deck height and track base, on the assumption that fording would be the normal way in which their tanks crossed rivers. A high deck gives greater fording depth, a lower pressure-per-square-inch figure gives ice-crossing and mobility in mud. If you start with generous height and trackbase requirements and then take back from the designer with weight limits, you are going to get a minivan --or, in this case, a tank with a distinctly pyramidal shape, which is good for armoured resistance.
Throw in a 3-inchish gun, and you've got the T-34, much to the excitement of German soldiers in the summer of 1941, who really weren't expecting Russian tanks to be any good.
I've heard the T-34 called overrated and the German response exaggerated. But who won the war? The Russians, that's who. Bearing the rule that you get roughly the performance you pay for in weight, it is hardly surprising that the T-34 was impressive. The German tanks of 1941 were graduallly growing towards 25t, and usually comparisons simply ignore the T-34's two man turret. If you give up an important quality, in this case crew efficiency, you get back savings you can apply elsewhere.
The T-34 is not the only tank of its OMG-what-happened-to-France generation. The Sherman, still in service when the Comet appeared, is of pretty much the same vintage, and if you apply the rule about getting what you pay for. . .
You know what? Let's just move on.
The Comet A-34 was not a revolutionary design. On the contrary, it almost seems to have been built out of the scrapheap. The original proposal was put in 1941 to Leyland Motors (and the Nuffield Organisation), firms already building its predecessor, the Cromwell. It is as good an illustration of the urgency of the war years as anything that the Comet was ordered before the Cromwell was even in service. Notice that: we're talking about how rates of technological progress speed up and slow down, and I have used the word "urgency." To replace the Cromwell smoothly, the Comet had to use as many of the components of the Cromwell as possible --something of a challenge when the components of the Cromwell were not quite determined yet!
The one feature definitely carried on was the Christie suspension used in the Cromwell. Cutting through the jargon, the Christie suspension is a conventional automobile spring-and-hydraulic cylinder combination. This gives a lot of play, and so good cross-country mobility, but tends to increase the height of the machine, so the springs were attached to a bellcrank that transformed their action by ninety degrees, and put in a compartment between the hull and the tracks. At the expense of sacrificing ease-of-maintenance and hull space and giving Sidney Horstmann a slow burn, Christie-suspended tanks got good mobility. Whether this was a good idea or not is an open question, since Horstmann's suspension returned on the Centurion, without any really noticeable problems. On the other hand, we are talking about a procurement decision driven by Lord Nuffield in the late 1930s, so it is perhaps inevitable that he would turn to one of those typically American half-charlatans-half-geniusses (exact proportions of ingredients may be varied to taste) that occupy such a large space of the British Non-conformist imagination. It turns out to be quite exciting to even try to understand what it is that Mr. Christie invented, and we can probably leave it at that.
The second major automotive feature that comes up with the Comet is the engine. The outlines of this story are well known. Before WWII, Rolls-Royce was a company with a large automobile business as a sideline to military aeroengines. Air attacks having forced the company into dispersal, the main works at Derby were emptied out of various divisions, many of which ended up in scenic Belper, just north of Derby. One of those, a "derelict, rat infested, rusty corrugated-iron group of buildings, built on a slag-heap overlooking the main railway line from Derby to Manchester," was selected for teh Chassis Department. Given that war had idled the automobile side, and the designers who worked over there, while other developmental teams were pottering about designing machine guns and cannons, and yet other projects had been abandoned for lack of design staff, you have to wonder what was going on at human resources, even before learning that the new head of the Division was So A. W. Robotham, and former technical assistant to managing director Ernie Hives. Not only that, but the recollections I am quoting from are from a new apprentice hire in the reconstituted Chassis Division Design Office. Evidently, while the division was sitting on its hands, as far as work goes, it was expanding into its new digs. This office was set to finishing a set of car drawings begun before the war, and mailing them to Canada. You know, so, in case of an invasion, when the New World, with all its power and might, stepped foward to the rescue of the Old, it would be able to do so with a new generation of Rolls Royces mid-sized salon cars. (Or, more prosaically, so they wouldn't be destroyed in an air attack.)Robotham, meanwhile, wandered over to Viale's shop and began tinkering with his 2 pounder cannon.
Also, the country was rapidly being turned into a junkyard for surplus Rolls-Royce engines. Time-expired Merlins were bad enough, but there were also plenty of 21L Kestrels from the late production runs, and, even more frustratingly, the all but unused Peregrines ordered for a massive, abandoned fighter contract. Something had to be done with them, and that something was tearing them apart to salvage reusable parts. And there was all of this approximately roofed and staffed space next to the rail-line next to Derby. . .
|It's very pretty, and some were even used.|
One can only imagine the enthusiasm with which the design staff at the drawing office greeted the opportunity to fufill their Dunkirk Emergency Sunday work requirement with the dirty, knuckle-busting prospect of tearing brand-new Peregrines apart for their piston rings and connecting rods! (Probably the people who had pushed for the Peregrine development were a bit embarrassed, too. I'm not quite sure who those were, but the selling point behind the Whirlwind was that it would be able to carry a cannon armament. . .)
Was there an alternative? The Nuffield Organisation had made everyones' lives as difficult as possible a few years before by demanding to be permitted to build a twenty-year-old (American!) 21L V-12 for its Christie-suspension cruiser tank. Now, with cruiser tank production ramping up, there was every prospect of a raft of new factories around the country being drafted into Liberty production, much to the advantage of the Nuffield Organisation. It was, perhaps, natural that the Clan Foundry staff would fiddle around with fitting a Peregrine into a Liberty tank engine mounting. However, to give Robotham due credit, he quickly gave up on the 21L Peregrine and turned to the 27L Merlin. Fifteen years of development, often directed specifically at fitting this much more powerful engine into the space vacated by a Kestrel, had given the Merlin a compact layour that was idea for a new concept: a 27L tank engine to be known as the Rolls-Royce Meteor.
Given that the whole point of the Kestrel-Merlin transition had been a push to use the new technology of pressurised glycol-water cooling, and the recent fiasco of the Covenanter's cooling issues, the rational response to this idea might have been something along the lines of, "Say what?" Instead, after a 27 ton Meteor-equipped tank prototype made 50mph on a closed track at Bovington, it was to throw money at Clan Foundry to solve all the other problems associated with pushing the old Crusader around with 600hp (400hp at the sprockets.) The heroic part of this was an increase in cooling fan efficiency from 30 to 60%.
Meanwhile, as we all know, because he has told us, many, many times, Air Commodore Frank Whittle had basically made a career out of pushing the RAF in the direction of the very rapid development and introduction of the comparatively low-tech "centrifugal" jet engine. This had proved to be something of an uphill battle for Whittle, for a number of reasons, not least among them some personality conflict issues elucidated at this link by Harry "The Hipster" Gibson. This (with less explicit reference to the effects of amphetamine abuse on bipolar personalities) is often invoked to explain why the Air Ministry approached Vauxhall and Rover to run factories to produce Whittle's jet engine, and not any companies which might have had previous dealings with Power Jet.
Or, old-time music aside, something else might have been going on. Three weeks ago now, I talked about the British "Shadow Factories" scheme. This was originally an extrapolation of the Agency factories which had made munitions in WWI. The Government built and owned the facilties, which were run by private businesses, which got a negotiated profit and an option to buy the factory after the emergency was over. This scheme had all sorts of industrial-policy related advantages in terms of encouraging factory development in "distressed areas."
Unfortunately, it also had a key problem, soon singled out by two prominent dissenters, Alvis and Nuffield. (Again.) While building airframes was one thing in terms of Agency experience, building aeroengines was quite another. The Rolls-Royce Merlin (for an example of immediate relevance that was not actually made under the Shadow scheme) was a 27L engine! Probably most car engines made in Britain in 1935 had less displacement than a single Merlin cylinder --which, to put it in perspective, is bigger than a 2L pop bottle. Combine that with the tolerance and weight constraints of the aeroengine business, and automobile engine manufacturers would basically have to learn a new business to involve themselves. Alvis and Nuffield were willing to do that, providing they got to keep the expertise embodied in the new works.
They wanted contracts to build their own designs, in other words. The two dissenters were read out of the business, although Nuffield got an equally large tank production contract a few months later, just as the Abdication Crisis was making the Government politically sensistive, and more compliant partners were sought. One of those was Rover, which was selected to build parts for Bristol aeroengines at a new plant at Acock Green.
One of the complaints heard from Alvis and Nuffield had been that the types of engines they were asked to build were likely to become obsolete quite quickly. They were not wrong. Bristol Mercuries and Pegasusses were to go into clearly long-in-the-tooth designs like the Blenheim and the Swordfish, but also the promising new bomber, the Wellington. but by early 1940, the Wellington had been switched over to the Merlin.
|A Vickers Warwick A/S Rescue variant, because for some reason I havent' a Wellington on my hard drive. And, yes, the Warwick did revert to a Bristol engine; but a sleeve-valve one, and that's an aspect of the story I just haven't time for.|
The Ministry of Aircraft Production, already in the habit of dreading Lord Austin's casual visits to talk about "Where's our profits right now now now," had a problem. The prospect of unemployed factories and unemployed Agencies had been in prospect from at least the midle of 1939, and arguably from the beginning of the Scheme. [See memos and reports reproduced here, starting p. 262]. So finding something for Acocks Green to do was a very urgent matter by early 1940, that had nothing to do with the ability to see the future and appreciate the prospects of the Meteor --and perhaps even less than is sometimes thought about the prospects of the jet.
At the same time, agency matters. Rover's design teams were soon working not only on the engine that would eventually become the Rolls-Royce Nene, but also something that, at least by genealogical courtsey, I will say, "would eventually become the Leyland 2S/350, for which seem somewhat further here, before the style nannies at Wikipedia revise the article into something more "neutral POV."
|The Rover JET1-gas turbine powered car., as restyled in 1952. By Stephencdickson - Own work, CC BY-SA 4.0, https://commons.wikimedia.org/w/index.php?curid=41632870|
This is all a bit sketchy. Having followed the links all sorts of places, I can vaguely gesture to the way in which Leyland and Rover developed their wartime engine experiences down sometimes-parallel and sometimes intersecting paths to finally yield a massive gas turbine engine intended for an abortive British high speed train project cancelled, of course, by Margaret Thatcher. Leyland gets into the story at the beginning, with Henry Spurrier hanging around Clan Foundry and arguing for his own company's proposed diesel as a Liberty replacement. It would take him another decade-and-a-half to get his way, and his company would have occasion to regret its success, but the developmental history of the Chieftain MBT's Leyland L-60 two-stroke, opposed piston multi-fuel diesel seems to trace its history back to the speculative sessions of 1940/1. Although the relationship between high power diesels and gas turbines is not always obvious, it is there. And, for that matter, Rover also experimented with a multi-fuel diesel in the late 1950s, this time a turbosupercharged one which drew directly on its gas turbine experience. After the British Army declined to buy it, it was fitted into an experimental, 129" inch "heavy duty" Land Rover; but the vision of Land Rovers running on peanut oil puttering around vast Groundnuts Scheme plantations in darkest Africa was . . . not to be.
|See how much easier life is when you give up on your personal creative vision and just go with the flow? I wonder if Peter Thiel drives one of these?|
So what I am saying is that Lord Nuffield was completely right when he suggested that participation in the engines shadow scheme was too important to the future of an integrated automobile maker in Britain for the company to participate in it on the Ministry's terms. Rover and Leyland, by agreeing to those terms and then . . . extending. . . them, did eventually get those benefits. Even if all of these science-fictional projects makes the advantage hard to see.
In the final stage of the story, of course, Robotham and his team turn the Meteor over to Rover, and carries the Nene --and the Rover development which became the Derwent-- back to his patron at Rolls-Royce, who, in 1941, announced that his company was going "all in for gas turbines."
And, well, that's it, though I've put the table of organisation and equipment details of the actual counterfactual down in a footnote. It shouldn't be "it," because there is also an interesting story to tell about the Comet's armament, but this post is long enough already, and has more than enough to chew over. When I started researching for this post at the beginning of the week, I thought that armaments, and the Merritt-Brown transmission, would turn out to be the big story, in part because the miracle of the Metor was so obscure. I had no idea about Rover and Leyland multi-fuel diesels and gas-turbine trains, sports cars and even trucks, and I did not see the connection until I fell into the secret of the Meteor: its remarkable cooling system.
Here I come back to State-led work, that of Griffiths and his team at NPL, and their long, mostly futile struggle to create an axial turbine jet that actually produced useful net thrust. The resulting work on the aerodynamic efficiency of compressor fans had direct implications on superchargers, but also on cooling fans. I'm a little reluctant to get into the German equivalent of the Meteor, the Maybach HL230, a 23L bored-out development of specially-designed 21L V-12 gasoline engine. However, I will note that it gave comparable power by running at 3000rpm (compare with the Meteor's sedate, governed 2350rpm). There are some pretty obvious consequences for maintenance when you begin throwing a 23L engine around at 3000rpm! As well, the high gas consumption of the Maybach points to the use of rich-mixture cooling.
So it would seem that cooling was the weak link in the Maybach development, and the late-war German tanks, in general. Conversely, the diffusion of experience with aerodynamically-advanced cooling systems in postwar British engine development in general.
So the way-too-late-to-be-short takeaway here is that if you want to bounce from Tech Level 5 to Tech Level 6 in ten years, you need a massive infusion of taxpayer monies into research and development. And, until proven otherwise, it would seem that wars are the crucial mechanism for sorting out good projects from bad in the absence of market discipline.
It's not like I'm saying anything new, here, of course. I just hope that the reader has got as much of a kick out of all the dieselpunk gadgetry in this post as I have!
*Some cutting and pasting for reading convenience:
|British Armoured Division, 1944: By Noclador - Own work, CC BY-SA 3.0, https://commons.wikimedia.org/w/index.php?curid=8290179|
British Armoured Division, May 1945 - Organization No. VIII Armored Division headquarters Company, with 7 Cruiser or Infantry Tanks 2 AA Tanks 1 Armored Regiment, with 55 Cruiser Tanks 6 Close Support Tanks 11 Light Tanks 6 AA Tanks 9 1 Armored Brigade Brigade Headquarters, with 7 Cruiser Tanks 8 OP Tanks 2 AA Tanks 3 Armored Regiments, each with 55 Cruiser Tanks 6 Close Support Tanks 11 Light Tanks 6 AA Tanks 1 Motorized Battalion 1 Infantry Brigade Brigade Headquarters Company 3 Infantry Battalions Infantry Support Group 1 Independent Machine Gun Company 1 Artillery Brigade Brigade Headquarters Company 1 Royal Horse Artillery Regiment (towed) 1 Anti-Tank Regiment 1 Field Artillery Regiment (self propelled) 1 AA Regiment Engineer Group Headquarters Company 2 Royal Engineer Field Squadrons 1 Royal Engineer Bridging Troop 1 Royal Engineer Field Park Squadron
Equipment holdings, British Armoured Division, May 1944 (same source): Equipment Motorcycles, Solo 853 Cars, misc. 390 Scout Cars 87 Armored Cars 3 Light Reconnaisance 10 Carriers, misc. 261 Trucks, 15 cwt 789 Lorries, 3 ton 1,309 Armored Cmd Vehicles 19 Armored Recovery Veh 14 Ambulances 36 Tractors, misc. 130 Tanks Cruiser 246 AA 27 Light 63 OP 27 Bridge layer 3 Trailers 219 Pistols 2,324 Rifles 6,689 Sten guns 6,204 LMG, Bren guns 1,376 HMG, Vickers Mk I 22 2" mortars 132 3" mortars 24 4.2" mortars 4 PIATs 302 25mm Guns 87 40mm Guns 36 40mm Guns, Self Prop. 18 25pdr guns, Field 24 25pdr guns, Self Prop. 24 (Sextons) 6pdr guns, Anti-tank 30 17pdr guns, Anti-tank 24 17pdr guns, M.10 AT 24
More details about the Comet tank than anyone probably needs, in a very-hard-to-read format. If you actually find yourself squinting to read it, don't bother, just go to the original, here.
The point of main relevance, which can be teased out of this screenshot from a source that repays a much longer visit but whose author forgets to mention his name is that the armour penetration of APCBC rounds fired by an 88mm KwK36, the antiaircraft gun that was the largest gun that the Germans could incidentally use as a field antitank weapon in 1940, is 110mm at 500m range, while the Comet's turret front armouor is 102mm. This may seem like an adequate margin, but it is unlikely that any APCBC was issued to the German air force flak units in 1940. Anything less than the 88 was helpless in the face of the Comet's armour.
Does this mean that 261 Comets would have romped on to Berlin? Suddden attacks by "unstoppable" tanks happened often enough in WWII that we have strong grounds for thinking that they would have produced localised crises rather than general routs. The initial impetus against even the most overmatched force
was eventually dissipated by logistical considerations. (In the Red Army's case, one has to suspect that the tanks in question had been issued without proper maintenance support.)
All this said, the solution to a sudden attack by invincible tanks is to retreat to a defensible antitank stop line. Had Army Group B done that, the war would certainly not have been lost --but the great offensive would have been over.