The best 'Re-builds' of WWI Capital Ships for WWII

This is a long and quite technical post, but I needed to do some background research as reference for a series of future articles. this follows on from Part I - Defining a Battleship - where I discuss the 'balance' or armament, armour and speed in detail.

Real Battleships of WWII - Part II - The best 'Re-builds' of WWI Capital Ships for WWII

Following on from the previous article, the more I listened to You-Tubes comparisons of warships by Drachinifel, Navyreviewer, and by Ryan Szimanski, the more I kept coming up with.. 'surely that can't actually be right'.

My 'surely not' discussion of what makes a Real Battleship is in the previous post.

As another  'surely not' example, British ‘rebuilds’ of World War One vintage battleships are often criticised in several books for not going nearly far enough in 1939, while Italian and Japanese 'rebuilds' are congratulated for what was not commissioned until late 1940 or mid 1941 (some of which didn't actually go nearly as far). Some commentaries even make statements about how good American rebuilds were, by sampling a few largely unmodernised ships that were sunk in late 1941 at Pearl Harbour and not re-commissioned until late 1944! 

So 'proper rebuilds' will be the discussion point for this article.

Full Modernisation Rebuilds

Everyone did at least some major refits of their Great War vintage ships. Everyone.

In fact many countries did 2 modernisations on most of their ships. 

Usually they started in the 20's with additional armour, AA guns, torpedo bulges, main gun elevation, fire control, and often engine upgrades (particularly conversion from coal to oil). Even the Soviets upgraded their Gangut class dreadnoughts, but I will pretty much ignore those as being of little relevance to WWII.

By contrast proper late 1930's- early 40's major 'Rebuilds' of Great War ships, are really only those rebuilds that completely changed the combat value in speed, firepower or protection of the vessel: to upgrade it enough to make it genuinely competitive with a 1930's or 40s new-builds. 

I am going to focus on proper 'rebuilds' that created up to date and competitive vessels, not incremental 'improvements' that still left their recipients incapable of facing modern ships. But only a very few of these rebuilds actually brought Great War capital ships up to competitive WWII battleship standards. 

In fact I would argue that some of the best 'rebuilds' were those that converted inadequate Great War dreadnoughts into quite good WWII 'cruiser-killers', rather than pretending to renew them at battleship level.

The Italian Jobs...

The Italians for instance did some very comprehensive, interesting, (and expensive), full rebuilds of their 4 pre Great War design 12" dreadnoughts. The 2 Conte de Cavour's being recommissioned in the late 30's, and the 2 Andrea Doria's in 1940. Uniquely, their 12" guns were bored out to 12.6", and, (in return for the removal of the fifth 'Q' turret amidships), they were all lengthened, re-engined, their speed upgraded from 21 to 26 or 27 knots, and both their deck armour and AA equipment substantially improved. (Though without any Dual Purpose options, they kept an inefficient mixed secondary battery of low angle and high angle guns). 

But the enormous effort and cost may have been misspent. Some commentators note that the expense of each reconstructions was almost enough for a brand new Littorio class battleship, and the delays in armour production for these rebuilds slowed the production of the Littorio's by years. 

And the results were simply not capable of facing any modern ship larger than a Deutschland, or even any older ship with bigger guns or heavier armour than a 12" Dreadnought like the French Courbet class, or the USS Arkansas. They certainly couldn't face any completely unmodernised Revenge, Ise or Nevada and have much chance. Let alone a Nelson, Nagato or Colorado. The main value of their reconstruction was to give them the speed to run away from such opponents.

These Italian rebuilds finished as excellent 'cruiser-killers', and fast enough to run away from most of the pre 30's battleships that could smash them. (Except the 'fast battleship' Hood, and other cruiser killers like the Renown's, Dunkerque's and Kongo's... all of which were frankly much superior combat ships). 

But nothing in the Italian rebuilds made them capable of winning an engagement with any proper WWII battleship, and probably only the Kongo's in the battlecruiser class.

Would the Italians have been better off in 1941 with 4 commissioned (or fitting out) Littorio's, simply backed up by 4 more modestly refitted 12.6" ships; rather than with 4 expensive but not very adequate rebuilds and only 2 Littorio's ever actually making it into service? 

Almost certainly the answer is yes.

The French Gamble...

By contrast the French did very little to their 3 Courbet class 12" dreadnoughts (the only 'capital ships' left by '39 still mounting a pair of side by side waist turrets), apart from a basic modernisation that partially replaced their coal fired boilers with oil ones, increased elevation of the guns, and added some AA. The 3 Bretagne class 13.4" super-dreadnoughts deservedly had a little more work, and Lorraine had her Q turret removed to fit aircraft. But all 5 ships remained slow 20 or 21 knot ships, and their maximum 10" armour belt was a bit dubious for facing even other Great War 12" 13.4", 13.5", 14" or 15" designs, let alone the newer ships entering service post war. 

Frankly the French apparently simply accepted that it was more cost effective to build new Dunkerque's and Richeleiu's rather than copy the Italian expenditure on ships that were a bit too small, lightly armed, and lightly armoured, to face modern battleships. Their minimal upgrades were probably still adequate to take on the Italian full rebuilds, or the German new build Deutschland cruiser killers, but realistically their main value in WWII would have been defensively as convoy escorts, or just for shore bombardment. (Though they could have operated alongside other marginally modernised ships like Texas for Torch or Overlord, or Mississippi at Surigao Strait, without looking at all out of place.)

Would the French have been better off in 1941 (if they had made it that far) with 2 Richelieu's in service (and another completing), 2 Dunkerque's, and the 6 lightly refitted 12" and 13.4" ships, than if they had done an Italian style 5 rebuilds of marginal ships, and not even got one of the Richelieu's complete? 

Definitely.

So what really made 'rebuilds' worthwhile?

Let's concentrate on how effective the total modernised armament of 're-build' were, particularly for WWII operations, and particularly on the rebuilds. 

Specifically, let's look at proper AA for modern war fighting.

Dual Purpose Secondary Batteries

Perhaps if any of the Italians, Japanese or the French had done rebuilds that did a proper conversion to real Dual Purpose secondary batteries, there might have been more value to such rebuilds. Rebuilds like Renown, Queen Elizabeth & Valiant, and eventually Pennsylvania, Nevada and Tennessee, did produce significantly improved ships suitable to front line service against modern builds. But Italy didn't even use DP for the secondary batteries of her new build's, let alone for any of her rebuilds.

So, let's look at DP.

The superb American 5"/38 is often called the best dual purpose gun of the war (which I agree with... mid war), largely on it's high rate of fire for AA, and the vast barrage it could throw up. (though notably it took 1,000 shells per kill, so the actual value was volume of deterrence...) In fact it had a similar rate of fire to the British 4" but a heavier shell, and was much faster than the 5.25", and a little bit faster than the 4.5". But all the British AA guns, and particularly the 4.5" and 5.25" outranged the 5"/38 by anywhere up to 6 or 7 kilometres. 

[Enemy planes had to keep a much greater distance from British ships for most of the war, and, as radar direction (and proximity shells) improved, range counted. Japanese planes flying comfortably out of range of the 5"/38 in 1944 and 1945 could sometimes get a nasty surprise when sniped out of the air with a single shot from one of the British Eastern or Pacific Fleet's 4.5" or 5.25". (If you were facing the Luftwaffe or the Japanese in 1939-43 RN destroyers would have killed for the elevation and rate of fire of the 5"/38, but facing German X-bombs or Japanese Kamikaze's in 1943-5 the USN would have killed for the range and accuracy of the 4.5" or 5.25". Frankly they were all good guns for a given purpose, and each had strengths and weaknesses which must be fairly assessed. The 5"/38 was certainly the best barrage AA gun of mid war: but the radar guided, power loading, proximity exploding, 4.5' or even 5.25", was certainly a better sniping AA gun by late war.)]

The Italians, the Germans and Japanese, never actually advanced as far as DP secondary batteries. For the Germans, there was never any consideration of rebuilding their only old 'capital ships'... the two ancient pre-dreadnoughts that had long since been relegated to coastal gunboat status. The Japanese also failed to fit DP into any of their modernisations. But it is surprising that all 3 of them failed to fit DP secondary batteries to their new builds either! The fact that the Duetschland's, Littorio's, Bismarck's and Yamato's all stuck with an inefficient mixed battery throughout shows how far off the pace their designs were. Not helped by the fact that virtually none of their AA guns were particularly effective. 

[Note Yamato's 6.1" secondary triple turrets were theoretically DP, but they were really too low angle and and slow traversing/firing. Their AA function is more comparable with the flechette rounds ships like the Revenge class could fire – apparently very effectively when you read about the Mediterranean convoy battles – from their single casement guns.]

[As an extra aside, the light 25mm AA guns the Japanese stuck with throughout were also a sign of falling off the pace. The USN dropped reliance on the dreadful 1.1" AA, and their quad 50's as fast as they could (though 1.1" continued to serve throughout the war on some ships), and the RN also sought to replace their quad MG mounts wherever possible , and even gradually replaced the considerably more effective 2 pounder Pom-Pom's: as both navies bought in better 20mmm and 40mm alternatives. (Though the Pom-Poms, like the 5"/38, were sheer rate of fire weapons – rather than the longer ranged and more accurate alternatives like 40mm Bofors or 4.5" and 5.25" respectively – and the octuple Pom-Poms found a new lease of life due to their unmatched volume and sustainable belt fed fire was facing Kamikaze's in 1945, when it was realised the 20mm lacked adequate stoping power for Kamikaze's). But the Japanese were forced to soldier on with the very unsatisfactory 25mm to the end, and it had to not only fill the 20mm slot of the Allies, but also cover the 40mm slot as well. It was deficient at the first, and totally inadequate for the second.]

Advantages of proper DP

The true value of a secondary DP armament is that it is vastly more space and weight efficient than having secondary batteries separated into low angle and high angle guns. Replacing 10-12 single casemented low angle guns, and 4-8 single high angle guns, with 16-20 DP guns in mechanised twin turrets, improves both functionality and efficiency out of all proportion to mere numbers. Even turreted low angle and high angle mixes in their new-builds aren't nearly as efficient. Advantages of proper DP include single magazine's instead of two sizes of shells; single supply shafts; plus reduced weight overall; which also led to considerably better armour options for both gun mounts and ship.

The RN, French navy, and USN did all go for proper dual purpose turrets in all their post Great War and later 1930's treaty designs and builds. But the 1920's Nelson's, the mid 30's Warspite rebuild, and 1940's Richelieu's new builds, still suffered from a more limited ability DP 6" secondary battery, as well as additional proper AA 4.7" or 3.9" respectively tertiary batteries. (The first and last at least had real DP batteries, but in two sizes, so without the magazine and armour advantages of a single calibre). 

The Japanese went half way with their rebuilds, with their modernised ships getting a mix of reduced low angle and limited number of turreted high angle guns. In effect their half way was usually similar to what was achieved with the Warspite (the first Queen Elizabeth to get a full modernisation), which was left with 8 old 6" low angle, and 8 new 4" DP in twin turrets. But while the British 4" AA was one of the best AA guns of the war,  the larger Japanese 5" AA had only half the range. 

Whereas the Dunkerque's, KGV's, North Carolina's, Lion's, South Dakota's, Iowa's, Vanguard, Montana's etc, all had proper single battery DP with all the advantages thereof. 

But no one except the RN managed to get real DP secondary armament into their interwar 'rebuilds' of WW1 ships...

Rebuilds with proper DP

The 1930's rebuilds of Renown, Queen Elizabeth and Valiant, which had proper DP, will  be covered later, so let's finishing looking at everyone else.

The USN did the 1920's re-engine coal to oil and add some AA modernisations to all their ships, but not so much the full 1930's rebuilds. 

They had discussed interwar re-fitting proper DP guns on at least the 'big 5' (the 2 Tennessee's and 3 Colorado's), but never got around to it. The initial plans to do a conversion to 16 5'/38's in twin turrets in the early 1940's all proved too difficult, time limited, or expensive: so the compromise of putting 4 more 3' guns and a few quad 50 Calibre MG's on most ships was all that was achieved. (But the 'Big 5' did – mostly – get extra torpedo bulges between 1940 and 1942 to assist with being substantially overweight from their original design, and thus so low in the water that the effectiveness of their main belts were being compromised.)

So, no USN pre-treaty battleships was actually given  a 'rebuild' with a proper DP armament, until after Pearl Harbour. 

The old 12" Dreadnought Arkansas for instance, and the two 14" New Yorks, were all part of the Atlantic neutrality patrol in 1941, and all avoided being damaged at Pearl Harbour. As a result, apart from their 20's conversion from coal to oil etc, they were never substantially rebuilt. They just had their AA upgraded bit by bit as the war progressed, but never advanced beyond mixed secondary batteries.

The 9 14" super-dreadnoughts of the Nevada, Pennsylvania, New Mexico and Tennessee classes were all re-engined, and up-armoured a bit in the 20's and 30's, and received the 8 single 5" and most of them the 4 single 3" AA guns fit out, but were otherwise unaltered from their 1920's refits by the time of Pearl Harbour. 

Oklahoma and Arizona, were sunk there and never repaired. Pennsylvania was only lightly damaged, so went back into service ASAP with the same equipment, not starting a substantial rebuild until late 1942. Nevada was badly damaged, and went straight into rebuild. Both emerged in 1943 mounting a modern style DP battery of 8 twin 5" turrets similar to the most recent new-build ships. 

The 3 New Mexico's, like the New York's, were in the Atlantic, and not damaged, so never properly rebuilt.  

The Tennessee's had been scheduled for modernisation work in 1940 and 1941, but that was put off by the need to try and intimidate the Japanese. California was sunk at Pearl, and Tennessee damaged. Although Tennessee was put back into service for a few months, both were eventually rebuilt with the full DP secondary armament, going back into service in mid 1943 and mid 1944 respectively. (Finishing by far the most compact and balanced looking rebuild anyone managed: but probably understandable considering they were almost the last finished, so faced none of the compromises of the pre-war rebuilds.)

The 3 16" ships of the Colorado Class were basically 8 x 16" versions of the 12 x 14" Tennessee's. (But, given that the 16" delivered 50% more kinetic energy, this reduction to 8 guns was considered a possible improvement overall.) Substantial 1930's plans for modernisations of the 'Big 5' Tennessee's and Colorado's being eventually – and possibly sensibly – abandoned in favour of spending the money on new ships, nothing was done. 

Of the Colorado's only West Virginia got the full DP conversion in 1942 - September 1944 (again, only because of receiving very substantial damage at Pearl Harbour), with Maryland and Colorado just getting more single AA bolted on like most of the 14" ships. 

So of 15 USN capital ships (well 12 really... as the pre-WWI Arkansas and New York dreadnoughts still on the list were no more worth upgrading than the French Courbet's), only 5 – of the 7 sunk or damaged at Pearl Harbour – were ever actually rebuilt, and most of them were not finished until the last year or so of the war anyway. 

But even then, the 21 knots maximum speed of all these 'Standard' battleships kept all of them limited thereafter mainly to escort and shore bombardment duties for the rest of the war, which suggests that the Naval Board could have been right all along that money might indeed have been better spent on new, and faster, ships.

The Japanese by contrast did 2 major upgrades of all their ships, including a second that sort of fit the 1930's 'rebuild' category... except they don't manage proper DP rebuilds. 

The Fuso and Yamashiro, and the Ise and Hyuga, were re-engined, lengthened a bit, and had the elevation of their main guns increased. Some people suggest that they even came out a knot or two faster, but that is debatable once they start getting weighed down with more and more AA after 1942. (The Fuso class were apparently restricted to about 18 knots by 1944, and when the USN inspected the surrendered Nagato in 1945, they were astonished at the state of disrepair.) 

But these 'rebuilt' ships had very little improvement to their 12" belt armour, and none of them advanced beyond mixed secondary batteries. They were still definitely capable battleships for line of battle slogging matches – if they were close enough to see and hit anything, considering they never received proper radar guidance. But they were hardly equivalent to more modern builds – or proper DP rebuilds – for WWII AA conditions. 

In fact  Drachinifel makes the point that most Japanese battleships had inferior armour to Germany's WWI battlecruisers! Which makes the enormous sums spent on rebuilding them look a bit Italianesque. But in reality the rebuilt ships were excellent given their limitations, and it  appears the Japanese simply accepted they simply had to do the best they could with what they had.

The even more substantial rebuilds of the elegant Kongo class battlecruisers, which started in the mid 30's, (though Hiei was still completing in early 1940): also suffered from lacking a modern Dual Purpose armament. Their lengthening and new engines lifted their 27 knot design, and made them proper 30+ knot ships, but, apart from a bit more AA, the improvements stop there. Their armour remained inferior to any WWI battlecruiser, let alone to anything they might actually face in WWII. Frankly re-designation as 'fast-battleships' is not convincing compared to any real battleship, let alone the Washington Treaty ships they later faced. 

Armour Issues.

Even the substantial armour additions (particularly to deck armour) of the Kongo rebuilds, didn't bring them up to the level of an only slightly modernised WWI Renown class battlecruiser like Repulse, let alone anywhere near the relatively unmodernised Hood. The completely rebuilt Kongo's upgraded slightly from 6" belts and finished with 8" belts, compared to the relatively unmodernised Repulse's 9" and Hood's 12". Which is a problem considering that the British admiralty always tried to keep the Renowns clear of real battleships, because they considered their armour insufficient to face more than the German 11" or Italian 12'6" guns. (Renown shrugged off multiple hits from Scharnhorst and Gneisenau during the Norway invasion while damaging both of them enough to encourage them to withdraw.)

Considering Hood's 12" belt, and even more her deck armour was – rightly – considered in need of upgrade by WWII, the Kongo's compromise on an 8" 'upgrade' to her belt is worrying. (The Dunkerque had a far more modern 9" belt angled at 11 degrees, which was easily penetrated by 2 British 15" shells at Mers El Kebir.) 

Even the completely obsolete and largely unmodernised French and American dreadnoughts had 30%-50% thicker armour than the Kongo's. 

[Worth looking at the previous article to see the discussion of armour QUALITY as opposed to merely thickness.]

Even if the Renown classes 9" belt was apparently pretty close in quality and effectiveness to the 10" - 11" of the older French, and Japanese ships, and the new build Littorio's, and actually not far off the 12.1" or less of most of the American and Japanese battleships: no one really wanted Repulse to try and go toe to toe with even an unmodernised real battleship.

Battlecruiser level vulnerability

But returning to the Kongo's 'upgraded' 8" belt', to quote the Wikipedia article on the Kongo's...

 "Even after these modifications, the armour capacity of the Kongō class remained much less than that of newer capital ships, a factor which played a major role in the sinking of Hiei and Kirishima at the hands of U.S. Navy cruisers and battleships in 1942."

It is fair to note that the reason the Kongo's had such an active war was that they were considered expendable cruiser killers, rather than proper line of battle ships. (Notably the Japanese 'Kantai Kessen', or 'Decisive Battle' plan had, apparently since the Battle of Tsushima, suggested that the aircraft carriers, destroyers, cruisers and even battle-cruisers would do waves of suicide attacks on the advancing US fleet, particularly at night, paring it down – and tiring it out – prior to facing the fresh and undamaged Japanese line of battle in daylight.)

So while most of  the Japanese battleships - particularly the Nagato's - led a pretty inactive war, as they were all held close to the main islands awaiting the Kantai Kessen, only the Kongo's really wandered all over the East Indies, Indian Ocean and South Pacific.

The loss of Hiei at Guadalcanal was actually due to damage from 8" cruiser fire (her steering knocked out by a single 8" cruiser shell, leaving her as helpless given how far from safety she was, as Bismarck or Prince of Wales's torpedo hits left them). 

Kirishima at least managed to put the brand new South Dakota in serious danger when a similar lucky stroke that knocked out the US ships power supply. But she didn't get a chance to finish the US ship off. Instead Kirishima was rapidly reduced to impotence by several radar guided hits from Washington's 16" guns, which left her with no functional main armament and massive flooding. The supposed 'solution' to these Kongo class weaknesses, was that the surviving ships – Kongo and Haruna – received a rough and ready increase to 'protection' with concrete 'armour' added to some spaces!

But have a look at the punishment real battleships could take. Bismarck and Scharnhorst took dozens of hits and still fought. Even the outdated 12" armoured battleship Yamashiro kept fighting back when facing 6 USN 14" and 16" armed battleships 4 8" and 4 6" cruisers at Surigao Strait. These ships give an idea of how even the oldest properly armoured battleship could still go toe to toe with other 14"+ armed battleships in a way an 8" or 9" armoured battlecruiser could not hope to! 

Other Innovations for Rebuilds

Other RN style innovations also led the capital ship field even before anybody did 'rebuilds'. Certainly Nelson style ‘tower-bridge’ rebuilds on Warspite, Renown and the Queens – and of course on the KGV's and Vanguard – were considerably better developments for space, weather protection, and stable mounts for radar and range finders. They allowed superior capacity for fighting a ship than the assorted towers, pagoda's and open bridges of brand new German, Italian, Japanese or American construction coming on line 20 years after Nelson was launched. (Though the French also adopted the 'tower' idea for their Dunkerque's and Richelieu's.)

And there were other design features the RN had settled on interwar, from the Nelson's to the KGV's and Lions, that hadn't made it into most other navies concepts.

The only truly 'post Washington' designs, the Iowa's for instance, still had pre-Nelson style bridges; Hood - Nelson style internal angled belts – which the KGV and Vanguard discarded as too limiting on space and too difficult to repair; Nelson style DP – though in this case the far superior 5"/38 of course; pre-Nelson style armoured conning towers – which the RN had greatly reduced as too much weight too high up for too little purpose, and which, interestingly, the USN stripped out of all their post Pearl Harbour rebuilds; and the Iowa's even still maintained angled fronts of the turrets – which the KGV had replaced with flat fronts, because the angled fronts dated from WWI short range engagements, and actually assisted enemy shells in the expected longer ranged engagements of 30's designs.

[It is also interesting that the 40's designed Alaska class battlecruisers came out with a central hangar and crane fittings, like the British 30's rebuilds and the KGV's, (but a feature dropped in the equivalent early 40's rethought designs for the Lions and the Vanguard). A somewhat weird compromise design (almost like the equally pointless British WWI experiments with Courageous and Glorious in concept), the Alaska's modern 12" guns were probably better than the WWI 14" ones, but the Alaskas certainly had inadequate armour for their own guns – let alone to face modern battleships guns – and also virtually no torpedo protection at all. Given that their AA was more cruiser scale than battleship, they didn't even make particularly good fast carrier escorts. More like Kongo cruiser killers's than the properly modernised DP battery of Renown. Some more Baltimore class cruisers would have probably been much better value for carrier escort. Of the six Alaska's started, only 2 were completed, and neither was used in service for even 3 years, with both being decommissioned by 1947! Szimansky is completely incorrect to claim that they could be considered battleships. They couldn't even be considered battlecruisers. Their only real contemporaries were the Duetschlands, and, like them, the correct title is 'large heavy cruisers'. Even the Italians got better value from their rebuilds than the USN did from these cute, expensive, but not particularly useful new builds.]

Were the Axis rebuilds worth it?

If the goal of the expenditure on rebuilding the Italian ships or the Kongo's was to have fast ships suitable for carrier escorts (remember the Italians and Germans were both building such carriers); and ships that could kick the backsides of enemy cruisers (the original concept of battlecruisers/cruiser-killers); and run away from the much slower French and USN battleships (or the slower 80% of British battleships) whenever they liked: then they were a good investment. 

But, particularly for the Kongo's, if the goal was to give them the sort of AA firepower that properly modernised British and American capital ships provided as carrier escorts, it was a fail. 

If the idea was to make the Kongo's genuine fast battleships capable of facing even the oldest or lightest real battleship, it was probably a worst waste of money than the Italian rebuilds.

In fact I think the Italian rebuilds and the Kongo's were excellent battlecruisers/cruiser killers, and well worth the upgrade money (even without a proper DP fit out). In fact I still thin the Kongo's were the best value capital ships the Japanese deployed in WWII.

But I can't be having with the idea that they were in any way classifiable as actual battleships.

The proper British 'rebuilds'.

In contrast to the commentary in too many books, Britain generally did much better on conversions. 

Or, at least, was doing considerably better on conversions... 

Or at least was starting to, but ran out of time...

A bit of context.

The 4 16" G3 class battlecruisers (fast battleships really given their extremely strong armour protection), and 4 18" N3 class battleships Britain started post war to respond to the Japanese 8-8 program and the USN 10 battleship program, had all the benefits of Britains much greater wartime combat experience, and ability to test captured German battleships. The G3's in particular had, on a displacement of just 48,000 tons, superior armour, guns and speed to any ship produced prior to the 33% larger 63,000 ton Yamato class designed 20 years later. In fact the Yamato's theoretically came closer to the slightly slower but 18" N3 design, but N3 had superior armament and much better armour than Yamato (top quality 15" British belts being much much stronger than uncooked and brittle Japanese 16.1" belts), and the only loss for N3 being 15,000 tons lighter was 4 knots slower speed! (Even the K3 'battlecruisers's' 14" armour belt and 8" decks were probably superior to Yamato's armour, and they did 5 knots faster despite being 15.000 tons lighter!)

In fact, given their superior armour technology, speed, and prototype dual purpose secondary armament of mixed heavy, medium and light AA, both the G3 and N3 were still more technically advanced than the 1940's Yamato design. The British ships as designed in 1920 certainly had a better balanced and more effective AA battery than the Yamato's actual 1941 fit out, which particularly suffered from not having any medium AA at all.! (G3 as designed in 1921 had 16 6" DP in 8 turrets, 6 single 4.7", and 32 2 pounders, and 2 quad MG's. N3 had 16 6", 8 4.7", 40 2 pounders and 4 quad MG's as designed. Both would have had extra AA in 1930's refits, let alone in WWII upgrades prior to December 1941. The 21 years later Yamato only started 1941 with 12 5" in 6 turrets, 24 25mm, and 2 twin MG's...)

According to Drachinifel's You-Tube review of the G3 and N3, had the G3's been built in the 1920's, they would have been "the Queens of the Sea" in WWII, and in the 20's immediately outclassed everything else afloat – including all those expensive new Japanese and American ships – in the same way that the original Dreadnought had outclassed and made obsolete every pre-dreadnought. (Ryan Szimanski commented in his You-Tube review of them, that just the threat of starting to build the G3's let the British "win" the Washington naval treaty, by trading not even started ships for half completed ships. A bit of an exaggeration, but not an unreasonable point.)

The G3's/N3's weren't built. But, as the only truly pre-treaty, unrestricted, comprehensively new, post war designs: they provide the benchmark for measuring everything that came after them. (For comparison – or lack thereof – see the Italian Carricciola's, the American 1920's design South Dakota, or the Japanese Tosa's, just to see what Drachinifel meant by calling the K3's the 'Queens of the Sea'.)

Still the Treaty limited 1923 'O3' class, or Nelson class 'compromise' battleships (sometimes referred to as the 'Cherry Tree' class, because they had been 'cut down' by Washington...) were not only the most powerful battleships afloat in 1939, but had been the first battleships actually built with innovative G3/N3 style features like 6" secondary armament in twin DP turrets. (Though note, although it was theoretically DP from the start, and had excellent elevation, it was not really fast enough in traverse or rate of fire for really effective battery fire DP use early in WWII. It was not until radar directed, long distance, proximity fused, 'sniping' became possible very late in the war, that it was really anywhere near effective as a proper DP secondary battery. Unlike most other 6" secondary armaments – prior to HMS Tiger – it had the elevation and the range for AA, but not the necessary speed of traverse or rate of fire.) 

Whereas the only really good DP secondary battery actual rebuild's by any navy pre-war were the 20 4.5" DP in 10 turrets of Renown (finished 1938), Valiant ('39) and Queen Elizabeth ('40).

Real Comparisons

So in terms of proper DP 'rebuilds' we are only comparing British ships rebuilt pre-war and recommissioned in 1938 and 1941, with US ships damaged or sunk at Pearl Harbour and recommissioned in 1943 and 1944.

With this in mind, it is pretty hard to take seriously the dismissive statements about RN reconstructions offered by too many writers like H. P Wilmott (in Warships - Octopus, 1975)... "Those British ships that were rebuilt failed to hold their speed as the American and Japanese ships had done: although their armour was thickened, little could disguise their all round inferiority to their contemporaries..."

That attitude is reflected, presumably unthinkingly, by too many commentaries. 

Frankly it doesn't hold water. 

Certainly Britain would have liked to get more full rebuilds done before getting into a war, and would have done so, had her war waited until 1941. But the rebuilds she did get done by 1939-40 were considerably better than most other nations produced in time for Pearl Harbour, or even after Pearl Harbour. 

In fact the 10 twin 4.5" DP turrets (the same models as on the Illustrious class carriers and some of the dedicated Dido AA cruisers) used on the late 30's rebuilt Queen Elizabeth, Valiant and Renown, were never exceeded in AA effectiveness by any other battleships DP battery. Not on anything rebuilt after Pearl Harbour, nor really on any brand new ship commissioned by any navy during the war. (They were even superior to new build USN battleships with 20 5"/38, simply due to their much greater range.)

Had the European war start been delayed from a September 1939 start, to a December 1941 start, Britain would have completed or been completing similar 20 x 4.5" in 10 turrets conversions to Repulse, Barham and Malaya. And the Hood rebuild (see Drachinifel again), was probably going to get the same 8 twin 5.25" armament as the KGV's. So the plan was to have 6 or 7 of 8 completely modernised rebuilt capital ships with modern DP armaments (plus the 2 less efficient DP Nelsons) completed or half finished, by approximately the time of Pearl Harbour, compared to none at all with modern DP for the rest of the world's navies.

Not sure how that works with Wilmott's... "although their armour was thickened, little could disguise their all round inferiority to their contemporaries..."

Comparing to the RN's 3 genuine rebuilds, the phrase "all round inferiority" is simply fantasy.

Is Wilmott right that not enough was done?

Having dismissed Wilmott's criticisms of the quality of the RN rebuilds, still doesn't alter his point that the RN (or more accurately the UK Treasury) was lax not to achieve more between the wars. More full DP rebuilds, or at least more substantial upgrades.

It is certainly true that the RN only comprehensively rebuilt 4 of it's 15 capital ships - Renown, Valiant and Queen Elizabeth, and to a lesser extent Warspite – before the war interrupted the process. If that is what Wilmott meant, it might be quite fair to say that more should have been done...  Just unrealistic given treaty restrictions, Depression budgets, and the minor fact that Britain was already years ahead of everyone else at this task...

On the other hand, with Nelson and Rodney already having limited DP, the slightly earlier comprehensive Warspite rebuild only suffering from not having the full DP option, and those 3 proper DP rebuilds, there is also a fair argument that only 4 of the 9 other possible ships - specifically Repulse, Barham, Malaya and Hood – were actually worth substantial re-building. And even having 6 out of the 10 practical possibilities actually completed or under way as fully functional DP ships in 1939 was still way better than the no full DP rebuilds at all in any other navy in 1941. (With the French new built Dunkerque cruiser killers as the only other capital ships in the world with a DP secondary armament in 1939.)

Rebuilding the 4 other suitable vessels would have been good value, but, frankly, thoroughly rebuilding the 5 Revenge class would have been a complete waste of money and resources. The British simply considered them unworthy of major reconstruction compared to the better value of new builds. 

Unworthy of rebuild?

It was also a bit unnecessary. Given their earlier upgrades to armour and other equipment, the Revenge's were pretty competitive, at least with anything of their own vintage. The Revenge's were still far tougher designs than any of the French or Italian or American or Japanese pre-WWI designs like Arkansas, New York, Nevada, Courbet, Bretagne, Conte di Cavour,  Caui Dulio, or Fuso. 

In fact they were tough enough to stand a reasonable chance of slugging it out even with later designs like Nagato, Colorado, Littorio, Bismarck or even the Washington's or Iowa's... at least at closer range.  (In the 1936-8 Parliamentary Debates on Naval Estimates, the fact that the Revenge's were officially to be retired as the KGV came on line was fiercely debated, as their value even only partially modernised was still clear. It was noted in these House of Commons debates that 'circumstances might well change' before then, requiring them to be kept... at least in a suitable role... Which, as Churchill suggested in those debates, was clearly as heavy convoy escorts that would deter any possible convoy raider.) The unmodernised Revenge's certainly chased Scharnhorst's and Littorio's and lesser raiders away from many convoys during the war.

In fact one of the Wikipedia articles on one of the class - Ramillies - is clear that the class was still reasonably competitive... "On 30 May, Japanese midget submarines that had been launched by the submarines I-16 and I-20 attacked the ships in Diego Suarez. One of the midget submarines scored a hit on Ramillies just forward of her "A" turret on the port side. The explosion tore a large hole in the hull and caused extensive flooding, though damage control teams quickly contained it and prompt counter-flooding prevented her from listing badly. Still down by the bow after offloading most of her ammunition, she was nevertheless able to steam to Durban, South Africa, at a speed of 9 to 10 knots (17 to 19 km/h; 10 to 12 mph). There, she was inspected by the Constructor H. S. Pengelly, who noted that "although the vessel is now 26 years old and felt by most to be of little value owing to reduced size and slow speeds, the Ramillies is in exceptionally good shape, and I should wonder whether or not the capital ships of today with their lighter scantlings would survive a blow as well as this old girl, some 26 years after they were built..."

But most importantly, even these 'unworthy of rebuilding' ships had, by 1939-40, been re-fitted with 8 modern 4" AA guns in twin mounts, 16-24 2 pounders and 8-16 MG's... an equal if not superior AA battery to any other WWI vintage ship in any other navy prior to the Pearl Harbour rebuilds. (And they had all received extra AA upgrades between 1939 and December 1941.) Given that the 8 5"/25 calibre individual mounts on all USN battleships had much less effective range and accuracy, and it is best not to mention the 1.1" backup: the next closest AA comparison in other navies in 1939-1941 was the Nagato class rebuilds's, which also had 8 somewhat less effective 5" in 4 twin turrets, and 20 of the very poor 25mm. (And in fact only the 4 rebuilt Italian ships, and the 2 Dunkerque and 2 Scharnhorst class new builds of any other navy actually had roughly equivalent AA to the the Revenge's 1939 armament until the Richelieu's, Littorio's and Washington's started to arrive in 1940-41.)

Were the British rebuild investments worth it?

I have stated that the large amounts spent on the Italian and Japanese rebuilds usually did not lift them to a level that could face WWII contemporaries. Most of the value spent on teh 4 Italian 'battleships' and the 4 Kongo class battlecruisers, was actually just to provide good cruiser killers that could run from most real battleships. (Though I acknowledge that the Nagato's and Ise rebuilds were notably closer to modern standards of battleships than the relatively unmodernised Revenge's or any of the US standards.)

So was the RN also wasting its money trying to bring old battleships up to modern standards?

Well, no.

Frankly the 1939-40 rebuilds – Renown, Queen Elizabeth and Valiant – were, on the basis of their superior DP and AA capabilities if nothing else, simply better rebuilds than anything else afloat until those few USN ships sunk at Pearl Harbour started turning up again in 1943 and 1944. And the Queens were already 3 or 4 knots faster than those USN rebuilds, and of any other WWI ship except the Italian lightweight rebuild 12.6" dreadnoughts (which were incapable of facing them), and the 4 Japanese ships which had similar or slightly better speed, (but without a modern DP armament).

Only the Kongo's might potentially be considered better value rebuilds, mainly due to their upgrade from 27 to 30 knot speed giving their 14" guns the ability to keep up with fleet carriers. But, like the Italian rebuilds, this really only made them of value as the type of ships that Szimanski refers to as 'cruiser killers'. Such rebuilds in no way made them suitable to stand in line of battle against even obsolete battleships. 

The Kongo's real comparison there is with the rebuilt Renown. But Renown was not only faster, but better armoured (Renown's 9" higher quality belt being more like 10.5" when properly compared to Kongo's 8"), and with a vastly superior DP secondary armament, (and therefore far more suitable to carrier escort). So even there, the Kongo rebuilds fail to match their only real contemporary.

The 3 real RN rebuilds, and even the half done Warspite, were definitely good value.

Were the Japanese rebuild investments worth it?

The Kongo's real issue is lack of proper armour. They simply could not face any other still existing battleships more modern than 12" Arkansas or Courbet's. (Probably not even those at most ranges.) Even the Italian 12.6" 27 knot rebuilds would have given them trouble (though it would be an interesting fight), and frankly even the slightly faster, 11" gunned, radar equipped, Scharnhorst's would have kicked their arses. The weakness of their armour made them even less suitable to facing other capital ships than the Queen Mary battlecruiser which, despite having a heavier belt than the greatly rebuilt Kongo's, had exploded when facing 11" dreadnoughts at Jutland. Taking a Kongo within range of 14" or 15' (let alone 16") battleships, was simply suicidal. (See Guadalcanal again.)

It is a pity really, because otherwise the Kongo's could have been as good as fast carrier escorts as Renown. But without a DP armament, they were really only cruiser killer escorts, and could not add much useful AA escort in the way Renown's massive battery could. Considering all the money spent on the Kongo rebuilds, the lack of a good DP secondary battery undermined their end value significantly.

[Side Reflections...]

[Some of these YouTubes reflect on whether having the rebuilt Renown, with one of the best AA batteries in the world, escorting the Prince of Wales in 1941 would have had a substantially different results for Force Z. Not really a dumb question, though the POW's actually very good 5.25" DP had been 'mission killed' early in the fight by a simple power failure. Note that POW – like Bismarck, Vittorio Veneto, and South Dakota – were all modern ships, that were all 'mission killed' early in the war by lucky hits on propellor shafts or by power failure in battle. POW unfortunately by both, which caused her sinking, and Bismarck by just one, but too far from port to recover. Vittorio Veneto and South Dakota were both very lucky to survive similar failures, and in their cases it owed more to having other ships nearby to assist with their survival and recovery, than to any superiority in design. (Notably wartime damage control experience meant that there were no such later failures in other ships of these same classes!)

Another of my old posts queries the really quite stupid assumption that had the aircraft carrier Indomitable been with Force Z, she would have just been lost with POW and Repulse... Obviously an assumption made by people who have never looked a the great Mediterranean convoy battles of 1941 and 1942 where one or two carriers CAP's often held off several hundred German and Italian bombers, sometimes for days at a time... But read that discussion here.]

Could the RN have spent the rebuild money better?

We still have to ask whether it would have been better to devote the same resources spent on these RN rebuilds to new builds instead. But in the RN case it appears not. 

The entire 1920's upgrades of 13 RN capital ships was only about 3 million pounds all up, and even the far more comprehensive mid 30's rebuild of Warspite, was only about 2.3 Million Pounds Sterling. This was a third the price of a mid 20's 7 million for a Nelson new build, let alone a late 30's new King Goerge V class. Even though Renown's more comprehensive rebuild was more like 3.1 million pounds, the 4 rebuilds the RN did get done were practically new ships, quite capable of matching it with most new-built battleships, and they at least were powerful enough for both surface and AA actions to give the sort of combat value not possible from the far less effective Italian rebuilds. 

Getting the other 4 possible rebuilds done for about the price of another 1.5 KGV would have been a real bargain.

There is also the timing value of the RN rebuilds. Rebuilt ships available in 1939 or 1940 were actually vital to holding the line until new builds could come on line. As it was the KGV class suffered a little from being pushed into production in the 1936 and 1937 programs, rather than waiting a year to get the 'treaty clause' upgrades that gave 16" guns to their American contemporaries. But the 6 Lion class of the 1938, 1939 and 1940 programs (which were only dropped when war broke out, as were the USN's 1940 and 41 Montana's and later Iowa's when their war broke out): plus the rush compromise Vanguard in 1941, would have given Britain 10-12 modern ships PLUS 8 completely rebuilt and very effective older ships (plus 2 'modern-ish' Nelsons and 5 minimally modernised Revenge's) by about 1942-3. About 20 completely modern RN capital ships compared to a grand total of about 17 modern ships in the rest of the worlds navies combined. (4 German, 3 Italian, 2 Japanese, 2 French and 6 or 7 American... Which comes to 30 odd fully modern or modernised 'Allied' capital ships versus perhaps 9 'Axis'...)

So clearly the Admiralty considered that, at the cost of about 2.5 new builds, these 8 complete rebuilds  – almost all likely to be complete before Japan or the US even entered the war –would have been a very worthwhile investment. 

Pity they only got half of them done in time.

Still this 'just in time' approach compares to the French being caught out by their new build program not being advanced enough when they went to war, and not having any modernisations to fill the gap. Only the Italians, Japanese and Americans had long enough to get their new build programs actually working before war actually descended upon them.

Other possible rebuilds... had circumstances been different?

There are two specific reasons why the RN rebuilds worked so much better than the Italian ones. The 24 knot Queens, (and even more the 30+ know Renown's and Hood), were simply bigger and more spacious options for rebuild than any of the 21 knot ships (whether British or anyone else's), or any of the relatively under-gunned or under-armoured 12" or 13.4" ship.

Which meant that smaller older ships really weren't worth substantial rebuilds, and could probably make do with a minor 20s upgrade and some extra AA... if they were just to play second rank escort and bombardment roles like the Arkansas, New York, Courbet, Bretagne, Gangut, etc, classes.

Consider for instance the RN's 13.5" battleship fleet of WWI veterans, all scrapped pre WWII, (though several of which had stayed in commission until the early 30's), and all of which were better ships than those 5 classes of 10 ships named above. The lack of even some of these extra 13.5" ships was a sever problem in WWII.

Note that, unlike the French, Italian and US navies, which all had little choice but to kept 12" dreadnoughts in service into WWII to maintain some numbers: the RN had considered all of their 12" guns dreadnoughts ready for scrap post WWI. (Most of them had been pretty worn out by war service anyway, so the RN had no fantasies about any value in ever rebuilding them.) 

But  – had they not got the Washington Treaty through – the RN could easily have kept up to 13 of the 13.5" gun super-dreadnought or battlecruiser designs – many of them competitive with, if not considerably superior to, any of their contemporary French, Italian, Japanese or US 12", 12.6", 13.4" (or possibly even 14") Dreadnoughts that were still in service in WWII. 

(The only other Dreadnought of much value that any other navy might have kept in service, was the 26,000 ton 12" dreadnought Wyoming - sister to Arkansas. Possibly the previous 22,000 ton class of the Utah and Florida might also have been considered... but these ships were all more comparable to the completely obsolete Courbet's than to the more useful Bretagne's. The Japanese 21,000 ton 12" dreadnought Settsu – with her six turrets in a hexagon layout... four in side by side pairs – might also compare with a Courbet. Or at a pinch, the 19,000 ton Italian Dante Alighieri. But nothing else in existence would have come anywhere close to matching one of these British 13.5" super-dreadnoughts. But even keeping every single 12" Dreadnought scrapped by every other navy in the world in service, would only total 7 more 12" Dreadnoughts, compared to the 13 13.5" super-dreadnoughts and battlecruisers the RN disposed of between the wars.)

Several of the 12 British 13.5" super dreadnoughts could have been kept. The 3 surviving 1911 King George V class and the 4 1912 Iron Duke class – all 25,500 tons – were suitable for minor upgrades like the Revenge class. And possibly even the 3 surviving 1909 22,000 ton Orion class that preceded the KGV's. All were superior to any of the 12" designs like Arkansas and Courbet and Bretagne still in service in WWII. They were all probably just as good as the 14" armed New York's, Nevada's, and Fuso's. The last 7 at least – the KGV's and Iron Dukes – could probably even match adequately with the Ise's. They were certainly capable of keeping the more lightly armed or armoured modern Deutschland's, Dunkerque's, and Scharnhorst's (or modernised Kongo's) clear of any convoys... 

[This is where I query the line used by everyone from Wilmott to Szimanski , that the RN's numerical superiority post WWI was based on "worn out 12" (Wilmott) – and 13.5" (Szimanski) – ships in need of  replacement". Certainly Britain planned to scrap the dozen or so 12" ships, even the relatively modern Agincourt (the 28,000 ton wartime build taken over from Turkey, which was a potentially excellent rebuild option). But at least 10 of the 13.5" guns (if not all 13) were as valuable, if not more valuable, than many of the more obsolete ships kept going by other navies. Putting these 11-15 vessels into the reserve fleet would have been exactly the same decision that the USN made with the Iowa's in the 60's and 70's, (before Reagan brought them back for his 600 ship fleet in the 80's.) 

I think it was probably sensible to trade all the 12" and probably even some of these 13.5" ships (the 3 Orions presumably) for the Washington Naval Treaty, even if it allowed the US to achieve naval parity for no actual cost (which sort of makes a joke of Szymanski's suggestion that it was the UK that 'won' at Washington). 

But if the Washington treaty had not gone ahead, it is probable that not all of these 13 odd 13.5" vessels would have been scrapped. (In fact although the 1909 model Orions were immediate victims of the Washington conference, the 1911 model Iron Dukes were still in service until after the 1930 London Conference, and the 1910 model KGV's were only deleted late 20's. Without the Treaties, the last 7 at least might have served in WWII.)]

Imagine Germany even bothering to build commerce raider like the Duetschland's if the RN had a 7-10 extra 21 knot 13.5" capital ships in the reserve fleet for convoy duty? Theoretically these 13.5" ships could all have had the sort of 'remove Q turret and upgrade' rebuild of the Italian Dreadnoughts, but in reality if the RN considered the Revenge's not worth the effort, these ships would certainly have remained 'reserve fleet' units with certainly no more than the 8 4", 16 2 pounder, 8 MG (probably in direct swap for Q turrets space and weight) upgrades like those of the slightly bigger Revenge's. IE: 'merely' better WWII AA than any contemporary US, French, Japanese battleship...

But, even if they had been kept, none of the ten Orion, KGV or Iron Duke super dreadnoughts would actually have been any more worth rebuilding than the Revenge's. Only the 3 28 knot 'big cat' battlecruisers – Lion and Princess Royal (scrapped in the 20's – Washington Treaty) and Tiger (scrapped 1932 – London Treaty), all of them similar in design to the Kongo's – would have been worth substantial rebuilds, all delivering very nice fast additional ships that could have been given a Renown style work-over to make 'cruiser killer' carrier escorts with considerably better fleet AA defence than the Kongo's or Alaska's. 

Because the key element of making a rebuild truly worthwhile was really the extra length and space of the faster ships – the Queen's and the battlecruisers – which allowed more space for upgrades, particularly after re-engining and re-boilering released considerably more space below decks. The 20 4.5 DP guns could be fitted to these larger ships without much compromising speed, and indeed with significant increases in both armour and range. 

Real Value?

Frankly the DP AA armament of the 3 full rebuilds that Britain got done pre war was just as good as the post Pearl Harbour American rebuilds, and close to as good as brand new 'Treaty' British, French and American ships: and it is simply a shame that the Repulse, Hood, Barham and Malaya didn't get the same rebuilds in time.

[Drakinifel has a cute YouTube on 'what if' Hood had suffered battle damage engaging Bismarck, but not been sunk by a fluke shot'. Presumably she would have immediately gone into repair and been given the refit that had been planned for her pre-war (originally scheduled for 1942 to allow KGV's to complete, then moved to a late1941 slot anyway). The suggested rebuild was to come out with the 16 5.25" DP batteries in the same format as the KGV. Perhaps even using the far faster modernised auto loading 5.25" models being produced for Vanguard. It is obviously disappointing that the Hood, Barham, Repulse and POW were sunk outright instead of just damaged enough to be rebuilt. Had any of them been able to be salvaged like some of the Pearl Harbour ships, or escaped similar battle situations and battle damage for repair – like Gneisenau, Vittorio Veneto, Nelson, Ramilles or South Dakota – some interesting results might have transpired... With some of them possibly even refitted in American yards like the Nelson, Illustrious and Indomitable?]

So the proper DP RN rebuilds were a considerably better investment than the half arsed Kongo's, or even the more comprehensively rebuilt, but frankly inadequate, Italian dreadnoughts. 

And anyone doing damage repairs during wartime probably also got value from doing proper DP rebuilds where possible.

Had Capital ships reached their peak?

But  it is worth commenting that the brand new post treaty restriction WWII ships like the Iowa's, Vanguard, and even Yamato's, all looked surprisingly inferior in various ways to the (48,000 ton) K3/N3 battlecruisers/battleships Britain had started laying down in 1921. 

Szimanski makes the good point that although the Yamato's were bigger and tougher than Iowa's, their advantages just don't add up to justify an extra 15,000 tons (full load) of resources and expense. And he is quite correct, but then he fails to note that the same argument applies to Iowa's. At 15,000 tons heavier than (full load) KGV's, they had slightly superior DP and AA (as built, not by end of war additions), and maybe 3 or 4 knots greater speed (but only in good weather), but much inferior armour. For 15,000 tons advantage! 

The KGV's modern 14" guns repeatedly punched through considerably heavier armour than the Iowa's carried (the Bismarck's was at least 15% better, and Scharnhorst's more than 25% better), and were guaranteed to defeat Iowa's; whereas KGV's armour was much more likely to be able to withstand Iowa's guns, given that it was the only treaty period battleship design with armour actually designed to withstand 16" guns!

In fact for the Iowa's 6,000 tons extra over Vanguard, the Iowa's had inferior DP and AA weapons, greatly inferior armour, and indeed inferior speed in anything but calm weather for short spurts. For 6.000 tons more! 

The 13,000 ton smaller (full load) Richelieu's – despite lacking as good a DP secondary battery as the Iowa's – were both faster in most weathers, and much better armoured than Iowa's. 

Even being 19,000 tons more than a Nelson doesn't alter the fact that an Iowa's  6-8 knot speed advantage won't help much if the Nelson's 14" armour is pretty good against Iowa's guns, compared to Iowa's 10.5" equivalent being very marginal against Nelson's. 

(In fact Yamato, at almost 25,000 tons heavier than Nelson, only gets 4 knots advantage, and probably has less effective armour: and in most sea conditions, at most ranges, and certainly in anything other than perfect daylight line of sight: you would probably have to back Nelson's technically superior armour and radar guided guns against Yamato any time...)

As Szimanski notes, significantly greater tonnage, for minimal extra capacity, just reveals significantly inferior design effectiveness! 

That means you Bismarck, Iowa and Yamato...

The Iowa 'battleships' could have matched speed – in good weather – and main guns with similar sized K3 'battlecruisers', but with 30% - 40% lighter effective armour, couldn't even go close on protection. (Meaning that in reality it was an Iowa battlecruiser compared to a K3 battleship, not the other way around!).

The Yamato's, with heavier guns, and even a bit more armour, but 5 knots slower than a G3, actually come out a bit more like the N3 designs. But again, is that all you can manage 20 years later and for 15,000 tons more!

Although even bigger designs were played with during WWII, (62,000 tons for Montana's, 92,000 tons for one 'improved' Yamato's and one late war redesign Lion, and a purely fantasy 140,000 tons for one of the German H class): the battleship had apparently reached its logical balance of size and power versus cost effectiveness with the K3 and N3 designs, and the cost ineffectiveness of going much further was pretty conclusively demonstrated by the events of WWII. 

When the Admiralty dismissed the later wartime designs as uneconomic, it was simply because the cost of ever bigger ships for ever better defensive capability, would quickly outweigh the benefits of the strict limits of their offensive capabilities. (They decided when designing the K3/N3 that the offensive power of 8 or 9 heavy guns, simply wasn't worth the cost of more than 50,000 tons of investment... certainly not worth 70,000 or 90.000... the fact that you could keep building ever bigger and ever more expensive, did not mean that you should!)

The K3 design (with its plentiful tonnage and deck space for a possible DP upgrade), was probably close to the last word in how battleships might be formatted in an age of steadily rising airpower.

So some final comments on 'rebuilds'.

The Italians did some truly elegant work on rebuilding obsolete ships, but at dubious cost effectiveness considering the results could barely face the second or third rank capital ships of other navies. Frankly, although they got very nice cruiser-killers out of it, spending the same resources on new builds – as the French tried to – would probably have had a better return. But they had to answer the new Dunkerque's, and do it faster than new Littorio's were possible, so there is at least logic for attempting such rebuilds.

The Americans did some excellent rebuilds, but only on ships badly damaged or sunk at Pearl Harbour, and most of those weren't back in service until very late, and saw little wartime service except convoy escort and shore bombardment. Although doing the rebuilds while doing the necessary repairs made sense, the USN, possibly equally sensibly, didn't invest many resources in rebuilding their slow 'standard' ships pre war. Concentrating on getting 10 more modern battleships functional for 1941-44 instead was definitely a better choice. Lucky they got those precious 2 extra years of peace to get the process in train!

The Japanese 'rebuilds' saw substantial refits, particularly of engines, and in some cases lengthened hulls: which usually actually lifted their speed. But not much change to main armament or mixed secondary batteries, and certainly inadequate changes to armour for modern war fighting. The Fuso's and Ise's armour were barely adequate to face other modern capital ships, and the Kongo's apparently completely inadequate to cope with even heavy cruisers. The Nagato's were considerably better, but probably not actually enough better than even the partially refitted Queen's or Colorado's to make much difference. (Certainly not as good as the completely rebuilt Queen's and Colorado's with their  proper DP batteries.)

The only really valuable interwar rebuilds then, were the Renown, Queen Elizabeth and Valiant, all completed in 39 to 40, ie: in time to serve throughout WWII. (Amusingly, the newly rebuilt Queen Elizabeth, which was sunk in Alexandria harbour just prior to Pearl Harbour, and – like several USN ships sunk at Pearl and rebuilt – was repaired in a US shipyard and then re-commissioned in mid 1943; could easily have been further upgraded during that repair had that been appropriate. But in reality only the light AA battery of 40mm/20mm was significantly altered during this post rebuild 'refit', as there really wasn't much of greater value that could be achieved on such a hull, than had already been done.)

Ideal rebuilds never actually happened though. The Italians enlarged their ships, and increased their speed, but with inadequate guns or armour to face modern battleships. The Kongo's, with good guns already, were enlarged, and had speed increased, but their DP was very limited, and their armour was disastrous. The Queens were given slightly better protection, much greater range, and truly excellent DP, but not enlarged to allow faster speeds. And the Renown was fast and with great DP, but still lacked the armour to fight proper modern battleships. And the American post-Pearl Harbor rebuilds were still too slow, and in most cases weren't back in action until the war was almost over.

But there doesn't seem much doubt that a proper DP rebuild of a suitably sized and armoured  WWI ship was still a damn good investment for WWII.

If you could get it done in time to be of use...