London Naval Treaties have larger limits

[Johnrankins]

No to a significant or useful degree.

The tens of thousands if not hundreds of thousands of people hired doing so would feel differently. 104,000 naval personal would be needed alone , with the multiplier effect we are probably talking 200,000 + people having jobs. We aren't just talking a couple of battleships but a few of them plus a lot of cruisers, subs and destroyers. It would add up . It would also make the Wallies considerably more prepared for ww2 , particularly against Japan. Besides no one program was going to eliminate the Great Depression by itself.

 

[NOMISYRRUC]

Here are the OTL tonnage quotas of the 1930 London Naval Treaty.

IOTL heavy cruisers were 15 British Commonwealth, 18 USA and 12 Japan. Note that the US:Japan heavy cruiser ratio is 3:2 in hulls if not tonnage.

These are the tonnage quotas ITTL according to the most recent revision of the OP.

Subs are limited to 2,600 tons , with each country allowed 3 at 3,600 tons for a total of 70,000 tons. The UK is limited to 20 heavy cruisers with a total tonnage of 230,000, the US with 24 up to 270,000 total tons, Japan with 16 totalling 170,000 tons. Light cruisers are limited to 250,000 for the UK, 200,000 for the US and 150,000 for Japan. US and UK are allowed up to 200,000 tons of destroyers each while Japan is limited to 140,000 tons.

AIUI nobody wanted submarines that big IOTL except the French who didn't sign the treaty. I don't see why any of the major navies would want submarines big ITTL. AFAIK they wanted bigger tonnage quotas so that they could have more submarines, but not bigger submarines. In a way that's self-defeating because it could result in fewer submarines being built from a larger tonnage quota.

However, cruisers remain limited to 10,000 ton until the Second London Treaty increases it to 12,000 tons. Therefore:

United States
24 x 10,000 = 240,000 tons plus 30,000 tons that can't be used.

United Kingdom/British Commonwealth
20 x 10,000 = 200,000 tons plus 30,000 tons that can't be used.

Furthermore, the Royal Navy didn't want any more eight inch gunned heavy cruisers displacing 10,000 tons. They wanted six inch cruisers displacing 7,000 tons because they were cheaper to build and because they could build more 7,000 ton cruisers out of a given tonnage quota. The OTL RN didn't want better cruisers, it wanted more cruisers.

Japan
16 x 10,000 tons = 160,000 tons plus 10,000 tons that can't be used.

It's probably more than that because four of the OTL Japanese heavy cruisers displaced less than 10,000 tons. That's why their heavy cruiser quota wasn't 120,000 tons.

However, the 3:2 ratio of US to Japanese heavy cruisers has been maintained.

This is the difference between OTL and the OP in tons.

These are the percentage increases over OTL.

 

[NOMISYRRUC]

Here are the OTL tonnage quotas.

This is what I think they should be ITTL.

These are the increases over OTL in tons.

These are the increases as a percentage of OTL.

 

[Johnrankins]

Here are the OTL tonnage quotas of the 1930 London Naval Treaty.
View attachment 547395

IOTL heavy cruisers were 15 British Commonwealth, 18 USA and 12 Japan. Note that the US:Japan heavy cruiser ratio is 3:2 in hulls if not tonnage.

These are the tonnage quotas ITTL according to the most recent revision of the OP.
View attachment 547406

AIUI nobody wanted submarines that big IOTL except the French who didn't sign the treaty. I don't see why any of the major navies would want submarines big ITTL. AFAIK they wanted bigger tonnage quotas so that they could have more submarines, but not bigger submarines. In a way that's self-defeating because it could result in fewer submarines being built from a larger tonnage quota.

This is a "Japan is more threatening earlier scenario" and bigger subs mean longer ranges for the Pacific.

Japan's invasion of Manchuria is even more successful than OTL and invades the rest of China a year earlier than OTL which is more successful as well. Both are due to the fact that China is more divided and Japan is somewhat less harsh. This allows Japan to start building a bigger navy and worries both the US and UK more about the balance of power in Asia. Meanwhile Hitler is somewhat smarter about trade than OTL and trades more with the USSR for more metal and oil. Doenitz and Raeder convince him to increase the speed of building up the Kriegsmarine by 20% while the Heer and Luftwaffe are sped up as well as compared to OTL. With the naval race speeding up Mussolini shifts some of his army spending into the navy.

However, cruisers remain limited to 10,000 ton until the Second London Treaty increases it to 12,000 tons. Therefore:

United States
24 x 10,000 = 240,000 tons plus 30,000 tons that can't be used.

United Kingdom/British Commonwealth
20 x 10,000 = 200,000 tons plus 30,000 tons that can't be used.

Furthermore, the Royal Navy didn't want any more eight inch gunned heavy cruisers displacing 10,000 tons. They wanted six inch cruisers displacing 7,000 tons because they were cheaper to build and because they could build more 7,000 ton cruisers out of a given tonnage quota. The OTL RN didn't want better cruisers, it wanted more cruisers.

Japan
16 x 10,000 tons = 160,000 tons plus 10,000 tons that can't be used.

It's probably more than that because four of the OTL Japanese heavy cruisers displaced less than 10,000 tons. That's why their heavy cruiser quota wasn't 120,000 tons.

However, the 3:2 ratio of US to Japanese heavy cruisers has been maintained.

Let's up the quota to 15,000 per ship , add 80,000 tons to British light cruisers while subtracting from the heavy.

 

[NOMISYRRUC]

Let's up the quota to 15,000 per ship , add 80,000 tons to British light cruisers while subtracting from the heavy.

Let's not.

 

[NOMISYRRUC]

This is a "Japan is more threatening earlier scenario" and bigger subs mean longer ranges for the Pacific.

You're giving the Japanese the same allowances as the USA and UK so it doesn't help them.

A different 1930 Treaty with bigger tonnage quotas and different replacement rules is feasible because the all the navies would have wanted more ships if their governments were willing to pay for them.

Increasing the allowed size of individual ships in the 1930 Treaty is in 3 letters A, S and B, because they didn't want bigger ships IOTL and they wouldn't want bigger ships in any non-ASB alternative timeline.

Two 15,000 ton cruisers absorb 30,000 tons of Treaty quota. That's the equivalent of three 10,000 ton ships, four 7,500 ton ships (Leander) or five 6,000 ton ships (Arethusa).

There was still a relationship between size and cost in the 1930s (i.e. it's before the "steel is cheap" era). 15,000 ton cruisers are going to be considerably more expensive limiting the number that can be built on cost grounds as well as the size of the tonnage quotas.

So what you have effectively done is given all sides ships with the same improvements in quality, but because they extra size has consumed the larger tonnage quotas and because the ships are more expensive the number of ships is the same in spite of the larger budgets of TTL.

Therefore, no change to OTL if all the battles are fought by the same number of larger ships.

 

[Johnrankins]

You're giving the Japanese the same allowances as the USA and UK so it doesn't help them.

A different 1930 Treaty with bigger tonnage quotas and different replacement rules is feasible because the all the navies would have wanted more ships if their governments were willing to pay for them.

Increasing the allowed size of individual ships in the 1930 Treaty is in 3 letters A, S and B, because they didn't want bigger ships IOTL and they wouldn't want bigger ships in any non-ASB alternative timeline.

Two 15,000 ton cruisers absorb 30,000 tons of Treaty quota. That's the equivalent of three 10,000 ton ships, four 7,500 ton ships (Leander) or five 6,000 ton ships (Arethusa).

There was still a relationship between size and cost in the 1930s (i.e. it's before the "steel is cheap" era). 15,000 ton cruisers are going to be considerably more expensive limiting the number that can be built on cost grounds as well as the size of the tonnage quotas.

So what you have effectively done is given all sides ships with the same improvements in quality, but because they extra size has consumed the larger tonnage quotas and because the ships are more expensive the number of ships is the same in spite of the larger budgets of TTL.

Therefore, no change to OTL if all the battles are fought by the same number of larger ships.

What about getting rid of tonnage quotas altogether in 1930 then? They build what they want.

 

[NOMISYRRUC]

What about getting rid of tonnage quotas altogether in 1930 then? They build what they want.

No. Because I've spent days in "spreadsheet" hell working out a feasible TL.

 

[Johnrankins]

No. Because I've spent days in "spreadsheet" hell working out a feasible TL.

Point taken.

 

[NOMISYRRUC]

These are the OTL tonnage quotas.

These are the TTL tonnage quotas from the current version of the OP.

These are what I think the TTL tonnage quotas should be.

Cruisers

The British Commonwealth had the joint largest battle fleet and the world's largest merchant fleet. The Royal Navy calculated that it needed 25 cruisers for fleet work and 45 trade protection cruisers for a total 70 cruisers. Therefore, it wanted a cruiser that was fit for purpose, but it also had to be cheap enough to be affordable in the numbers required and to squeeze the maximum number of ships out of the tonnage quota. That's why I haven't increased the tonnage quota for heavy cruisers and put all the increase into light cruisers. The grand total of 500,000 tons is just enough for 70 cruisers if the light cruisers are a mix of Leanders and Arethusas.

The United States had a battle fleet that was the same size as the British Commonwealth's, but a smaller merchant fleet (and shorter trade routes). Thus the United States Navy didn't want as many cruisers as the Royal Navy. This was a stumbling block at the disarmament conferences of OTL because the USA wanted naval parity with the British Commonwealth, but it didn't want to build a large number of cruisers that it didn't want. Fortunately the Americans required cruisers with greater endurance than the British because they had to operate in the Pacific so it was possible to reach an agreement where they would be allowed similar tonnages, but the USA would build big cruisers and the UK small cruisers.

AIUI the USA wanted 24 heavy cruisers so I have increased their Category A tonnage quota to 240,000 tons (24 ships of 10,000 tons). The reason why I asked for the change from a 16 year service life to 20 years forward from 1st January 1920 to 1st January 1921 is to allow the 8 oldest Omaha class cruisers to become overage by the end of 1941 instead of the end of 1945. This would allow the construction of 24 Brooklyn class cruisers by the end of 1941.

The 12 heavy cruisers that the IJN possessed IOTL had the following displacements.

Therefore, I have increased Japan's Category A cruiser quota by 40,000 tons from 108,400 tons IOTL to 148,400 tons ITTL. This will allow them to build another quartet of 10,000 ton heavy cruisers and maintain the OTL ration of 3 American heavy cruisers to 2 Japanese heavy cruisers.

IOTL the Japanese cruiser quota was equal to 65% of the American cruiser quota. Therefore, I have increased their Category B (light) cruiser quota to 163,600 tons to maintain this percentage.

Destroyers

This is the only part of the OP as originally posted that bears any relationship to the aspirations of a first rate navy IOTL. That is the Royal Navy wanted 200,000 tons of destroyers, but ended up with 150,000 tons.

 

[CV12Hornet]

The 12 heavy cruisers that the IJN possessed IOTL had the following displacements.

Therefore, I have increased Japan's Category A cruiser quota by 40,000 tons from 108,400 tons IOTL to 148,400 tons ITTL. This will allow them to build another quartet of 10,000 ton heavy cruisers and maintain the OTL ration of 3 American heavy cruisers to 2 Japanese heavy cruisers.

Which the Japanese will be very happy about, since their plans for the Night Battle phase of the Kantai Kessen demanded at least sixteen heavy cruisers. This also has obvious benefits for the TTL Mogamis being built from the start for 10,000 tons.

They also now have about 70,000 tons of spare light cruiser tonnage. Good chance we see the Tones carry the 155mm gun, and also an earlier analogue to the Aganos for the two cruiser squadrons assigned to the battle line and to replace the Kumas as leaders to be converted into more torpedo cruisers.

 

[McPherson]

No. Because I've spent days in "spreadsheet" hell working out a feasible TL.

Ever written a 4,500 word ATL block and watch it vanish into the ether? Yup. So I second the motion!

 

[NOMISYRRUC]

Which the Japanese will be very happy about, since their plans for the Night Battle phase of the Kantai Kessen demanded at least sixteen heavy cruisers. This also has obvious benefits for the TTL Mogamis being built from the start for 10,000 tons.

They also now have about 70,000 tons of spare light cruiser tonnage. Good chance we see the Tones carry the 155mm gun, and also an earlier analogue to the Aganos for the two cruiser squadrons assigned to the battle line and to replace the Kumas as leaders to be converted into more torpedo cruisers.

I broadly agree.

IOTL the Japanese ordered 4 Mogami class in the First Fleet Replenishment Programme of 1931 and the 2 Tone class in the Second Fleet Replenishment programme of 1934. They used the 51,000 tons of "replacement tonnage" that was available.

My suggestion for the TTL Treaty increases the light cruiser allowance by 63,150 tons to 114,105 tons. That's enough for 12 ships with an official displacement of 9,500 tons. However, if it is combined with the extra 40,000 tons of heavy cruisers that are allowed 154,105 tons are available which is enough for 16 ships with an official displacement of 9,630 tons. Furthermore, the Takao class had an official displacement of 9,850 tons rather than 10,000 tons increasing the tonnage available to 154,705 tons, enough for 16 ships of 9,670 tons.

Therefore, I think the Japanese would build 16 cruisers with an official displacement of 9,670 tons, but they won't try to keep to that limit when designing the ships. I think that they will order 8 Mogamis armed with fifteen 6 inch guns in 1931 to the rebuilt Mogami design of OTL. Then in 1934 they'll order 4 Tones armed with eight 8 inch guns and 4 Tones armed with twelve 6 inch guns.

IOTL the IJN hand 18 large cruisers (all heavy) in December 1941 to fight the 27 large cruisers (18 heavy and 9 light) in the USN. ITTL the Japanese will have 28 large cruisers (16 heavy and 12 light) but the Americans will have 48 large cruisers (24 heavy and 24 light) on that date if they build all the ships that the are allowed to and I think they will.

They would need another 4 large light cruisers to maintain the 3:2 cruiser ratio. However, 154,705 tons divided by 20 ships equals 7,735 tons per ship.

IOTL the 10 light cruisers of the Nagara, Sendai and Yubari classes didn't become overage until 1942-45. However, ITTL the 4 Nagaras laid down in 1920 and displacing 20,680 tons became overage 1938-39 instead of 1942-43 because the "16-year rule" was changed from ships laid down before 1st January 1921 instead of 1st January 1920. This would be used to order 4 Agano analogues in 1934.

However, that was before I worked out that the TTL Treaty limits would increase Japan's inferiority in large cruisers. Therefore, I think that it's more likely that the Japanese will order 20 large cruisers to be completed by the end of 1939 in their 1931 and 1934 Navy Laws. 175,385 tons were available, which is enough for 20 ships with an official displacement of 8,769 tons per ship and about the same as the Mogami class as built.

 

[CV12Hornet]

Therefore, I think the Japanese would build 16 cruisers with an official displacement of 9,670 tons, but they won't try to keep to that limit when designing the ships. I think that they will order 8 Mogamis armed with fifteen 6 inch guns in 1931 to the rebuilt Mogami design of OTL. Then in 1934 they'll order 4 Tones armed with eight 8 inch guns and 4 Tones armed with twelve 6 inch guns.

I mean, they can plan that but I don't think they have the money, especially with the Yamatos taking priority in construction. They do need more and more modern small cruisers, which would be more financially palatable.

They certainly can't build 8 large cruisers all at once. They never demonstrated the capacity to do so.

 

[NOMISYRRUC]

I mean, they can plan that but I don't think they have the money, especially with the Yamatos taking priority in construction. They do need more and more modern small cruisers, which would be more financially palatable.

They certainly can't build 8 large cruisers all at once. They never demonstrated the capacity to do so.

I don't know enough to disagree about the building capacity or financial sides of your argument.

However, the extra cruisers are built under the 1931 and 1934 Fleet Replenishment Programmes and the first pair of Yamatos were in the 1937 Fleet Replenishment programme. IOTL 4 out of 6 Mogami/Tone class cruisers were completed before the Yamatos were laid down. So they don't compete for resources. See below.

Also Mogami and Mikuma won't have the defects that they had IOTL and won't need to be rebuilt, while Suzaya and Kumano will not have to be modified whilst under construction, which aught to save some money. Furthermore, they aren't rearmed with 8 inch guns ITTL, which saves money and allows the turret makers and dockyards to do something else.

I'm not against the Japanese building smaller cruisers if that fits their OTL wants better than what I have suggested. However, the Japanese being the Japanese will want to use all the tonnage that's available by the earliest possible date. Would 154,105 tons of medium size cruisers be any cheaper than 154,105 tons of large cruisers? It might be harder to build a larger number of small cruisers because more slipways would be needed.

 

[CV12Hornet]

I don't know enough to disagree about the building capacity or financial sides of your argument.

However, the extra cruisers are built under the 1931 and 1934 Fleet Replenishment Programmes and the first pair of Yamatos were in the 1937 Fleet Replenishment programme. IOTL 4 out of 6 Mogami/Tone class cruisers were completed before the Yamatos were laid down. So they don't compete for resources. See below.

Ah, right, forgot about that timing. That said, they are still competing against the battleship rebuilds and the Soryu and Hiryu.

Also Mogami and Mikuma won't have the defects that they had IOTL and won't need to be rebuilt, while Suzaya and Kumano will not have to be modified whilst under construction, which aught to save some money. Furthermore, they aren't rearmed with 8 inch guns ITTL, which saves money and allows the turret makers and dockyards to do something else.

Not nearly enough to fund four more heavy cruisers.

I'm not against the Japanese building smaller cruisers if that fits their OTL wants better than what I have suggested. However, the Japanese being the Japanese will want to use all the tonnage that's available by the earliest possible date. Would 154,105 tons of medium size cruisers be any cheaper than 154,105 tons of large cruisers? It might be harder to build a larger number of small cruisers because more slipways would be needed.

I do think small cruisers fit Japan's more immediate needs better. IOTL they only had two torpedo cruisers for working with the heavy cruiser squadrons. I'd think they'd want at least four and knowing their divisional structure might go for eight. But we'll stick with four. Add another four to help defend the battle line, nine to lead destroyers, and two for submarine flagships, that's 19 ships. Japan had only 17 light cruisers at the time. Four new CLs would allow for four Kumas to be rearmed as torpedo cruisers while also retiring the Tenryus.

Assuming 6500 tons like the Aganos, that the Tones are 6" ships and listed at 10,000 tons, toss in two Katoris... Well, that leaves Japan with another 59,000 tons. Another two Katoris and two Ooyodos alongside the Tones would knock it down to 32,000 tons. And then the Treaties suddenly cease to be meaningful.

For money? Delete the Mogami rebuilds and having to tinker with designs on the slips. For slip space? Small CLs had the advantage of being able to be built at many more smaller yards, notably the Sasebo Naval Arsenal, which OTL built three of the four Agano-class cruisers. There was also the Uraga dock company, assuming it stayed in business interwar, and the Yokohama yards that built the Katoris...

 

[NOMISYRRUC]

Not nearly enough to fund four more heavy cruisers.

It's worse than that because it's 4 heavy cruisers and 6 large light cruisers for a total of 16 instead of the 4 large light cruisers and 2 heavy cruisers built IOTL.

I accept that it won't be enough. It goes without saying, which is why I didn't. It will help though.

 

[NOMISYRRUC]

I do think small cruisers fit Japan's more immediate needs better. IOTL they only had two torpedo cruisers for working with the heavy cruiser squadrons. I'd think they'd want at least four and knowing their divisional structure might go for eight. But we'll stick with four. Add another four to help defend the battle line, nine to lead destroyers, and two for submarine flagships, that's 19 ships. Japan had only 17 light cruisers at the time. Four new CLs would allow for four Kumas to be rearmed as torpedo cruisers while also retiring the Tenryus.

Assuming 6500 tons like the Aganos, that the Tones are 6" ships and listed at 10,000 tons, toss in two Katoris... Well, that leaves Japan with another 59,000 tons. Another two Katoris and two Ooyodos alongside the Tones would knock it down to 32,000 tons. And then the Treaties suddenly cease to be meaningful.

For money? Delete the Mogami rebuilds and having to tinker with designs on the slips. For slip space? Small CLs had the advantage of being able to be built at many more smaller yards, notably the Sasebo Naval Arsenal, which OTL built three of the four Agano-class cruisers. There was also the Uraga dock company, assuming it stayed in business interwar, and the Yokohama yards that built the Katoris...

How many hulls is that? My brains been pickled from working out what I think the cruisers and destroyers might be.

The money saved by deleting the Mogami rebuilds and tinkering with the designs on the slips would also saves money to build more larger cruisers.

What you wrote about the slipways at the other yards might well be true. For what it's worth the Tone class was 85ft 3in longer than an Agano at the waterline.

646ft 4in Mogami class​

649ft 7in Tone class​

564ft 4in Agano class​

405ft 2in Katori class​

 

[NOMISYRRUC]

Japanese Destroyers

In both timelines they had 125 destroyers displacing 134,781 tons, but the TTL version of the 1930 London Naval Treaty meant that the Japanese could build an additional 34,500 tons of destroyers by the end of 1936 as follows.

IOTL 12 destroyers were built under the First Fleet Replenishment Programme of 1931 and 14 under the Second Fleet Replenishment Programme of 1934 for a total of 26, which I thought were to replace the 26,960 tons of "replacement tonnage" that could be built before the end of 1936. However, when I did the arithmetic the tonnage built exceeded the tonnage allowed by a considerable margin. (The displacements are the standard displacements in Jane's Fighting Ships 1939. They are what the Japanese said their standard displacements were, rather than their actual displacements.)

However, the last of the ships built under the 1934 Programme weren't completed until 1938. Another 6,080 tons became overage in that year and the underage destroyer Miyuki of 1,700 tons lost in a collision in 1934. However, these only reduce the discrepancy to 2,148 tons. It could have been that the Asashio class were intended to be additional ships of the 1,368 ton type, which reduces the discrepancy to 828 tons.

The Japanese also built 4 torpedo boats under the 1931 Fleet Replenishment Programme and were to have built another 16 under the 1934 Fleet Replenishment Programmes which displaced less than 600 tons and therefore weren't counted in the tonnage quotas. However, they were not a success and 8 of the 16 boats in the 1934 Programme weren't built.

If the two programmes were intended to replace ships that became available by the end of 1938 a grand total of 69,240 tons "replacement tonnage" would be available by the end of 1938. This was enough for 51 destroyers of 1,368 tons or 46 of 1,500 tons.

Therefore, ITTL the Japanese build 46 destroyers of the Aashio type, which officially had a standard displacement of 1,500 tons, but actually displaced 1,961 tons. 16 would be built under the 1931 Fleet Replenishment Plan instead of the 12 destroyers and 4 torpedo boats ordered IOTL. The other 30 would be built under the 1934 Plan in place of the 14 destroyers and 16 torpedo boats (8 cancelled) in the OTL version.

IOTL the Japanese had 120 surface torpedo craft at the start of the Pacific War. That is 108 destroyers and 12 torpedo boats. 68 destroyers would be of the Fubuki to Yugumo classes. ITTL they would have had 128 surface torpedo craft consisting of 128 destroyers and no torpedo boats. This would include 88 destroyers of the Fubuki, Asashio, Kagero and Yugumo classes.

 

[McPherson]

I will only comment that the Japanese are about 8 slips short. They have to build them to build the added cruisers. So where? Sasebo and Yokusuka are maxed out. Kure?