Starting September 1939, what could Britain build, rebuild or not build to have the best possible fleet for the war with it having already begun?
Other hinge include improving doctrine, tactics, shells and whatever else they could feasibly do in the duration of the war.
We've had many threads on interwar ww1 and pre ww1 fleets but this is obviously a bit trickier, a more confined space so to speak.
September 1939 feels a little late on the construction side; much of the die has been cast, at least for the first half of the war. The first four
Illustrious class carriers and
Implacable are already on the ways.
Indefatigable will be laid down in November. All five
KGVs are on the ways.
Lion and
Temeraire have been laid down.
QE, Valiant and
Renown are in hand for their full rebuilds. Most of the war time cruisers are built and nine of the Colony class have been laid down. Nine of the
Didos have been laid down as well. Martlets will be ordered soon but the folding-wing version won't deliver until August 1941. The fixed wing variants can only operate from escort carriers or older carriers with larger elevators, like
Eagle. The 'flight deck is the strength deck' carriers like
Ark Royal and the early armored deck carriers need to wait for the Martlet II. The Swordfish entered service in 1936, the Skua entered in 1938. Fulmar won't come along until 1940, IIRC.
As far as Construction: the light fleets likely won't complete in time for the war; why build them? I know their larger elevators will make them more useful as post-war aircraft grow, but who is going to know that during the war?
In hindsight, if we really are going to push forward a British Pacific Fleet late-war, I might suspend/cancel
Anson and
Howe and prioritize
Lion and
Temeraire. They'll be more suited to operations in the Pacific. Alternatively, complete
Anson and
Howe, but bulge them to provide better torpedo protection.
I would also push for more destroyers fitted like
Lance, Lively, Larne and
Legion, with four twin 4in DP, to give the fleet more heavy air defense. In addition, I might try to use US yards to construct US destroyers for the RN. IIRC,
Bensons and
Gleaves were built after Pearl Harbor to supplement the construction of
Fletcher-class. Getting a few flotillas worth of US destroyers would supplement the AA of the fleet and provide more destroyers. With more modern destroyers, get the older destroyers into convoy escort or off to places like Australia, Singapore and Hong Kong. Also with respect to AA, conversion of all C class cruisers to CLAA. They were better at AA than the
Didos, why not make the most of them?
Tactically, first and foremost, never take
Glorious out of the Med. When Dudley Pound was CinC-Med, and Lumley Lyster was her captain, the concept of an carrier raid on the RM at Taranto first came around. Lyster trained her crew constantly for such and operation. In my opinion, Judgement will be even harder on the Italian Fleet if
Glorious undertakes the operation.
Also, with the start of the war, move the large 50,000 ton drydock out of Malta and to Alexandria. Don't wait for an Italian declaration of war and have the drydock spend the war on the bottom of Valetta harbor. Cunningham will able to dock larger ships and won't be limited to QEs and Rs.
I do like Cryhavoc's idea for Singapore. I would put a couple squadrons of Hunt class destroyers there as well, rotating them out of the combat areas. Their range won't be a hindrance and they can present a constant patrol force in the South China Sea. The IJN will have to sink one if their operations are found out early on the 8th of December, but Singapore and the rest of the world would be alerted. By the same token, keep at least half of the T-class submarines there. Rotate them out of the combat zones to Singapore and back, as with the destroyers. Also, put a couple squadrons of those fixed-wing Martlets in Singapore to defend the naval base.
With the RAF having priority on aircraft, I can't see the FAA improving without leveraging US builders. If that means more US aircraft earlier, so be it. I think RN carriers were under-armed early on in the war. Giving them fuller air complements, even with older air frames, will improve their performance.
Sub hunting is a job for smaller carriers like
Hermes, Argus and
Eagle. Use one of them instead of
Courageous for early ASW work. If a U-boat gets lucky early in the war, it will still be a loss, but it will hurt less than the loss of
Courageous, Glorious or
Ark Royal.
When the time comes to form an Eastern Fleet, send a group of cruisers to reinforce the Hunt class in Singapore. Don't send Tom Phillips there, make his force a show of solidarity with Australia, basing in Indian (Colombo) and calling at Perth. And give him a proper fleet, with at least one carrier, two AA cruisers, two heavy and two light cruisers and couple squadrons of destroyers to partner with a pair of capital ships
I can't see intelligence getting much better, unless there could be more focus on the Italian naval codes.
By the time the BPF rolls around the FAA is maturing as weapon. I don't see much needing to change late war, the RN has learned all the lessons, some of them the hard way, but still learned.
My thoughts,