"Thought Exercise: No London Naval Treaty(Alternate History)" Topic

So, I'm been posting this idea around to various naval gaming and naval history sites I'm on for feedback. It's a what-if question that's pretty straightforward: If there is no London Naval Treaty signed, what does WWII at sea look like? Are there any major changes?

The LNT failing isn't that far 'out there' as far as alternate history goes. There had been an earlier attempt to Geneva in 1927 to get nations to sign on for a very similar treaty but negotiations broke down. For our purposes we'll assume negotiations break down in London too.

My understanding that without the treaty, we see the following effects:
1. No extension of the WNT battleship 'building holiday', so new Battleship to replace existing ships would be laid down starting in 1931.
2. No distinction drawn between 6" cruisers and 8" cruisers, no limits on cruiser construction
3. No additional limits on submarine construction
4. No additional limits on destroyer construction

The WNT would have remained in force until 1936 at least, and then a power could withdraw by notifying the other signing powers of their intent. For our purposes let's assume that all the powers adhere to the WNT until at least 1938 or so and then some nation (Japan being a likely culprit) publicly breaks with the treaty.

The Great Depression plays a role in what sort of construction could be feasibly undertaken, though I suspect some nations (again Japan most likely) would have undertaken new battleship construction hell or high water.

So, what do people think the knock-on effects of this would be a later world conflict (assuming it kicks off at roughly the same time and roughly the same way)? The most obvious one is that some portion of the fleets would be new-built battleships, not refitted WWI battlewagons. There is no end to the 'cruiser race' between the US and Japan. Do 8" cruisers become so common they serve as the new defacto capital ship in secondary theaters? Aircraft carriers are still restricted in total tonnage, UNLESS they end up below 10,000 tons. Would this encourage the design of cruiser/carrier hybrids or small fast carriers to provide air cover for cruiser squadrons (a favorite concept of mine)? What do Destroyers look like in this world?

Any thoughts, theories, criticism, whatever, greatly appreciated.

-Will

Since the Great War was the war to end all wars, the treaty was welcomed because of the money that would be saved.
As usual, the law abiding (more or less) abide by treaties, while those less inclined look for loopholes.
And, how enforceable is a treaty like that anyway?
The only enforcement is to denounce violations and to vow to make up lost ground. That gives violators a head start of at least 3 years.

Yes, that was the intent of the Washington Naval Treaty; prevent a new battleship building race between the US, UK and Japan. And it worked! The later London Naval Treaty was to keep the benefits of the WNT (chiefly the battleship building holiday) and add on new rules to deal with new issues that were occurring or foreseen (the US/Japan cruiser race, the possibility that Destroyers would turn in some sort of expensive 'not quite a cruiser' class, etc). Japan actually adhered to the treaties (WNT and LNT) right up to 1936, which probably actually is rather likely in this alternate timeline.

So, we're assuming that the London negotiations breakdown like they did in Geneva a few years prior. The battleship holiday is over and someone (Japan) lays down the first new battleship since British put the Nelson and Rodney on the stocks, as soon as the WNT permits it in 1931. What happens after? That's the question I'm pondering.

Final note, the treaty was supported by regular inspections of ships and shipyards; very hard to hide major warship construction. Though Japan (again!) was noted for shaving off tonnage on their displacement reports.

-Will

I imagine the US would have done something to update the South Dakota design from the 1920s. Twelve 16in guns would be pretty interesting.

I wonder what kind of effect the new focus on battleships would have had on navy aviation.

I wonder what kind of effect the new focus on battleships would have had on navy aviation.

Good question. The Americans, British and Japanese all historically tried to build right up the carrier tonnage limit but in this timeline there's new battleships being laid down much earlier. If economics (and the Great Depression would have occurred regardless of the treaty) forced the choice between battleships or carriers I would suspect fewer and smaller carriers would be laid down. Repeats of the Ranger rather than the Yorktown class for the Americans, for example.

-Will

So without a large carrier fleet, the Pearl Harbor attack becomes a 24 hour shore bombardment by the Japanese battle line and more extensive use of subs for infiltration?

I think without the carrier fleet there is no Pearl Harbor attack. The Japanese would take the Philippines and then try to ambush the USN fleet that would be operating under War Plan Orange. Carriers would be used though on both sides for scouting.

Yep I think Texas Jack is right; if Carrier development is curtailed probably no Pearl Harbor attack. The Japanese would try to execute their 'death by a thousand cuts' strategy while the US relies more heavily on the original Plan Orange.

Now it's not certain that carrier development WOULD drop off; but it's also probably true that extending the Battleship holiday into 1930's highly encouraged carrier development. In this No-LNT timeline different choices might have to be made.

-Will

Bankruptcy in 1933 and probably degeneration into military dictatorships of participating powers. The Average War Gamers dream.

Truthfully, I really doubt much would have happened different from the historical. Why? The economy. 1930 (the year of the LNT) was one year out from the onset of the Great Depression. And the impacts carried well into the following decade. The only thing I can see that would be different would possibly be the wholesale adoption of 16" main batteries for BBs. But a huge increase in building? Not likely.

One more thing. The reason why treaties such as the LNT and the WNT come into being is a wholesale desire for them. This can be driven by popular demand (such as the WNT) or economic reality (as with the LNT). Its noteworthy that the earlier Geneva attempt failed during an economic boon.