Aircraft Carriers
1929-35 IOTL
In 1924 the plan was to scrap Argus, Eagle, Hermes and Vindictive and the tonnage released would be used to build four 17,000 ton ships that would be completed by 1938 when the aircraft carrier force would consist of Courageous, Furious, Glorious and the four 17,000 ton ships. However, the two ships that should have been laid down by the Wall Street Crash weren't built. The ship that should have been ordered in the 1931-32 Estimates for completion in 1935 wasn't built either. The only ship that was laid down was Ark Royal, which was ordered in the 1934-35 Estimates, laid down in 1935 and completed in 1938.
At the same time the American and Japanese governments allowed their navies to build up to treaty limits by 1940. The Imperial Japanese Navy had the 81,000 tons of aircraft carriers that were permitted by the Washington Treaty by 1939 and the five ships (Akagi, Kaga, Ryujo, Soryu and Hiryu) were much larger than their official standard displacements. The United States Navy had 120,000 tons of modern aircraft carriers (Lexington, Saratoga, Wasp, Yorktown and Enterprise) by 1938 and the 135,000 tons permitted by the Washington Treaty and American Law (the Vinson-Trammell Act of 1934) was reached in 1940 when Wasp was completed.
IOTL HM Government didn't try to make up the lost time until the middle of the 1930s when the plan was changed to 14 aircraft carriers by the middle of the 1940s consisting of ten 23,000 ton ships, Ark Royal and the Three Follies. However, they were only able to build six of the ten 23,000 ton ships by the end of 1944.
1929-35 ITTL
The OTL plan in the first half of 1930s was to build five 22,000 ton ships accommodating 72 aircraft each for a grand total of 360 aircraft. At that time the Admiralty wanted the aircraft carrier quota reduced to 110,000 tons in the treaty that would replace the 1930 Treaty and 360 was the number of aeroplanes that the Admiralty wanted for the fleet. However, there would be enough tonnage left for a sixth 22,000 ton ship should the next treaty retain the 135,000 ton quota.
ITTL Cabinet approved the Admiralty's request for six 22,500 ton ships to be laid down 1932-37 and completed 1935-40. They would be built at the rate of one per year to replace the existing aircraft carriers and build up to the Washington Treaty's limits. The sixth ship was a spare to cover refits which would be in reserve in peacetime without an air group.
The four ships laid down 1932-35 were modified Ark Royals. The main modification was that they had conventional single-deck lifts instead of the double-deck lifts of OTL.
1935-45 IOTL
In both timelines the Admiralty preferred multi-role aircraft because it allowed greater tactical flexibility (if that's the right expression) and because it reduced the number of aircraft that were required, which was cheaper in itself and meant that fewer aircraft carriers were needed to accommodate them. IOTL the introduction of the torpedo-spotter-reconnaissance aircraft in the middle of the 1930s reduced the requirement for fleet aircraft from 360 to 300.
This reduction in the number of fleet aircraft requirement coincided with the abolition of the tonnage quotas under the 1935 London Naval Treaty and Rearmament. Therefore, the Admiralty could accommodate the 300 aircraft in a larger number of ships. Ark Royal was now rated as a 48 aircraft ship and the 252 remaining aircraft would be accommodated in seven 23,000 ton ships at 36 aircraft per ship for a total of eight fleet carriers.
The Admiralty had wanted some aircraft carriers for trade protection for years and the 1924 Plan included some ships displacing 10,000 tons whose numbers weren't limited by the Washington Treaty. However, these aircraft carriers weren't intended to escort North Atlantic convoys like the escort carriers that were eventually acquired IOTL. Instead they were to help the cruiser squadrons find and destroy surface raiders link the German panzerschiffen. As a result they had to carry enough TSRs to keep an adequate reconnaissance force airborne at all times and form a strike force capable of sinking a panzerschiffe. A series of sketch designs for ships displacing 13,500 to 17,600 tons carrying 18 aircraft was produced, but they weren't considered satisfactory and their estimated cost was £3 million, while a satisfactory 23,000 ton ship of the Illustrious class had an estimated cost of £4 million. Therefore, the 14,700 trade protection carrier carrying 18 aircraft in the 1936-37 Estimates was replaced by a 23,000 ton fleet carrier carrying 36 aircraft, that is HMS Victorious.
The requirement was for 5 trade protection ships. That is one to work with the four cruiser squadrons on the North America & West Indies, South Atlantic, East Indies and China stations plus one spare to cover refits. This produced a total requirement for 14 aircraft carriers in 1935 consisting of 8 fleet carriers, 5 trade protection ships and a training carrier. As already explained these would consist of ten 23,000 ships, Ark Royal, Courageous, Furious and Glorious by the middle of the 1940s. However, the three old aircraft carriers would be maintained in reserve without aircraft. The ten 23,000 ton ships would be ordered at the rate of two per year in the 1936-37 to 1940-41 Estimates.
Unfortunately, the 1935 London Naval Treaty included a clause which said that ships had to be laid down at least one year after their construction was announced. As a result the two ships in the 1936-37 Estimates (Illustrious and Victorious) couldn't be laid down until the middle of 1937. Rearmament created demand pull inflation and a balance of payments deficit. This forced HM Government to "ration" the number of ships ordered in the 1938-39 and 1939-40 Estimates with the result two aircraft carriers were ordered in these financial years (Implacable and Indefatigable) instead of the planned four. The outbreak of World War II meant the ships required to complete the 1935 Plan couldn't be laid down until the second half of the war because fighting the Battle of the Atlantic had greater priority and the shipyards were full of convoy escorts and replacement merchant vessels. The 3 Audacious class ships laid down 1942-44 were effectively, the seventh, eighth and ninth 23,000 ships in the 1935 Plan.
Ark Royal was built in 3 years and that was the planned building time for the Illustrious class. However, neglect of the Royal Navy between 1919 and the middle of the 1930s meant produced a naval armaments industry that couldn't cope with the sudden increase in demand. Matters were made worse by the outbreak of World War II. The construction of warships for the fleet like aircraft carriers were delayed by the ASW mobilisation, the invasion crisis, the expansion of the convoy system made necessary by the Fall of France, building more merchant ships to replace the higher losses, amphibious shipping and finally the fleet train that supported the British Pacific Fleet. The only ship that was completed close to schedule was Illustrious herself. Formidable was built in 3½ years. Indomitable and Victorious took 4 years to build. Implacable and Indefatigable were built in an average of 5 years. Eagle wasn't launched until May 1946 in spite of being laid down in October 1942 and because of Austerity wouldn't be completed until October 1951. Ark Royal was laid down in May 1943, but because of her low priority during and after the war wouldn't be launched until May 1950 and completed until February 1955 (although she would have been completed before the end of 1952 had it not been decided to fit steam catapults). The third Audacious laid down in April 1944 was only 23% complete when she was cancelled in January 1946. None of the Malta class had been laid down by the end of the war in spite of being ordered in 1943.
As already explained the Admiralty wanted the aircraft carrier quota reduced from 135,000 tons to 110,000 tons. It also wanted the maximum size of this type of ship reduced from 27,000 tons to 22,000 tons. However, the 1935 London Naval Treaty abolished the tonnage quota and only reduced the maximum size of an aircraft carrier to 23,000 tons. The Admiralty regretted this restriction and regretted it quickly. It was not long before it was decided that the Illustrious class didn't carry enough aircraft producing the Indomitable and Implacable sub-classes. The Illustrious class would have been much better ships had the limit been kept at 27,000 tons and the increase in the building cost would have been negligible in the scheme of the things because the Treasury had provided £1,500 million for rearmament 1937-42). It would also have include some unintended future proofing because it would have been easier (and therefore cheaper) to modernise the ships in the 1950s.
1935-45 ITTL
The Royal Navy of 1935 had the aircraft carriers Argus, Courageous, Eagle, Furious, Glorious and Hermes. In common with OTL Argus had been in reserve since 1928.
Under construction were four 22,500 ton modified Ark Royals that had been ordered 1931-32 to 1934-35, laid down 1932-35 and were due to be completed 1935-38. A fifth ship had been ordered in the 1935-36 Estimates and a sixth ship was planned for the 1936-37 Estimates for completion in 1940. The 1935 Carrier was to be laid down in 1936 for completion in 1939 and the 1936 Carrier was to be laid down in 1937 for completion in 1940.
The existing ships would become depot ships or be scrapped as the new ships were completed. Argus was to be converted to a depot ship for target drones (which was done IOTL). Eagle would be converted into a depot ship for the Mobile Naval Base Defence Organisation (MNBDO). Hermes was to be converted into a seaplane carrier. The other ships would be scrapped.
The TTL Second London Naval treaty retained the 27,000 ton displacement limit and abolished the 135,000 ton quota. This allowed the Admiralty to plan for a force of 14 aircraft carriers by the middle of the 1940s. In common with OTL this would consist of 8 aircraft carriers working with the fleet, 5 trade protection ships and a training ship. The force would be made up of the four 22,500 ton ships under construction and ten 27,000 ton ships. Each ship was rated with a capacity of 48 aircraft. However, the peacetime strength of the Fleet Air Arm of the Royal Air Force would only be 480 first-line aircraft in 40 squadrons of 12 because three of the 22,500 ton aircraft carriers would be in reserve and the fourth ship would be the training carrier.
The revised building programme was to build the 1935 and 1936 Carriers as 27,000 ton ships which would be followed by eight ships ordered at the rate of two per year in the 1937-38 to 1940-41 Estimates at the rate of two per year that would be laid down 1938-41 and completed 1941-44.
Six aircraft carriers were laid down after Ark Royal in both timelines. The TTL ships were built as follows:
- The 1935 Carrier was named Illustrious. She was laid down in the spring of 1936 and completed in the spring of 1939. The OTL Illustrious was completed in May 1940;
- The 1936 Carrier was named Victorious. She was laid down in the spring of 1937 and completed in the spring of 1940. The OTL Victorious was completed in May 1941.
- The two ships ordered in the 1937-38 Estimates were named Formidable and Indomitable. IOTL they were laid down in June 1937 and November 1937 which was six months to a year earlier than normal, but the Royal Navy wasn't as short of aircraft carriers ITTL so they were laid down in the spring of 1938. In spite of these delays the ships were still completed in May and November 1941 respectively. The extra ships that were built 1930-35 ITTL meant the naval armaments industry wasn't overstretched as badly after 1935. Furthermore laying Illustrious down in 1936 and laying these ships down in 1938 reduced the over loading;
- IOTL Implacable was ordered in the 1938-39 Estimates and Indefatigable was ordered in the 1939-40 Estimates, but ITTL both ships were ordered in the 1938-39 Estimates. Implacable was still laid down in February 1939 but Indefatigable was laid down in May 1939 instead of November 1939. The problems that existed after September 1939 IOTL also existed ITTL, so I'm going to be prudent and say that Implacable was still completed in August 1944. However, Indefatigable would be completed in November 1943 instead of May 1944 because she was laid down six months earlier;
- Two aircraft carriers were ordered in the 1939-40 Estimates and another pair projected for 1940-41 to complete the 1935 Plan in the spring of 1944. The 1939 Carriers were to be named Audacious and Irresistible. The 1940 Carriers hadn't been given names by September 1939 but they would have probably been named Inflexible and Invincible. IOTL Indefatigable the sole 1939 Carrier was laid down in November 1939, but ITTL the pair of 1939 ships were to be laid down in the spring of 1940 and were suspended in September 1939. They weren't laid down until October 1942 and May 1943 as the OTL Eagle (ex-Audacious) and Ark Royal (ex-Irresistible). The 1940 Carriers weren't due to be ordered until the spring of 1940 and effectively became the third Audacious laid down in April 1944 and Africa the ship ordered as the fourth Audacious but re-ordered as the fourth Malta. In common with OTL none of the three ships laid down 1942-44 had been launched by September 1945 with Eagle still completed in October 1951, Ark Royal completed in February 1955 and the 1944 Eagle cancelled in January 1946.
The Situation in September 1939 IOTL
Ark Royal, Courageous, Eagle, Glorious, Furious and Hermes (six ships) were in commission. Furious was the deck landing training ship and the others were operational warships. Five aircraft carriers were under construction and a sixth was on order. I haven't counted Argus because she was serving as a depot ship for De Havilland Queen Bee target drones.
The five operational aircraft carriers had an aggregate capacity of 15 squadrons if Ark Royal was rated as a 48-aircraft ship and the Naval Aviation (which was as the Fleet Air Arm's official name form May 1939) had 15 aircraft carrier squadrons with 9-12 aircraft each for a total of 162 aircraft. However, six squadrons were embarked on Ark Royal instead of four and Courageous had two squadrons embarked instead of four.
There were also 70 seaplanes and amphibians operating form 2 seaplane carriers (Albatross and Pegasus), capital ships and cruisers.
The Situation in September 1939 ITTL
There were ten aircraft carriers consisting of one brand new 27,000-ton ship, four ships of the 22,500-ton type, Courageous, Eagle, Furious, Glorious and Hermes. Furious was the deck landing training ship and the remainder were operational warships. Five aircraft carriers were under construction. Two more were on order, but they wouldn't be laid down until 1942-43.
The 27,000 ton aircraft carrier was named Illustrious. The 22,500 ton ships were named Benbow, Emperor of India, Marlborough and Ark Royal. The 22,500 ton ships were built in that order and were known as the Benbow class.
In common with OTL Argus hasn't been counted because she had been converted into a depot ship. Her entry in the OTL edition of Jane's Fighting Ships 1939 had her in the depot ships section rather than the aircraft carriers section and that was also the case in the TTL edition.
The nine operational aircraft carriers had an aggregate capacity of 31 squadrons because the Benbow and Illustrious classes were rated as 48-aircraft ships. The TTL Naval Aviation had 366 aircraft in 31 squadrons with 9-12 aircraft each.
There would also be at least 70 aircraft assigned to the seaplane carriers, capital ships and cruisers. The number of extra aircraft depends upon the number of battleships that were fully modernised ITTL and the number of extra cruisers that were laid down between 1929 and 1936 ITTL.
The Plan in September 1939
The TTL Victorious was due to commission in the spring of 1940 and four new squadrons were to be formed by the end of March 1940 to form her air group. That would bring the total number of carrier aircraft up to 414 organised into 35 squadrons of 9-12 aircraft. Her completion would also bring the Royal Navy's aircraft carrier strength to 11 ships consisting of ten operational ships and a training carrier.
The TTL Formidable and Indomitable were due to commission in the spring of 1941. They would replace Eagle which would be converted into a depot ship for the Mobile Naval Base Defence Organisation (MDBDO) and Hermes which would be converted to a training ship. Their air groups would be formed from the 3 squadrons currently aboard Eagle and Hermes and 5 new squadrons to be formed in the 1940-41 financial year. That would bring the total number to 480 aircraft in 40 squadrons of 12 because Eagle's squadrons would be increased from 9 to 12 aircraft.
The TTL Implacable and Indefatigable were planned to complete in 1942. The Royal Navy would then have 13 aircraft carriers consisting of six 27,000-ton ships, four 22,500-ton ships, Courageous, Furious and Glorious. The ten newest ships would be operational aircraft carriers, Furious would still be the training carrier, Courageous and Glorious would go into reserve. No increase in the number of Naval Aviation squadron was required because the air groups of Courageous and Glorious would transfer to Implacable and Indefatigable.
The two ships ordered in 1939 were scheduled for completion in 1943. They would take the place of Benbow and Emperor of India which would go into reserve. In common with the Implacable and Indefatigable the 1939 Carriers the new ships would take over the crews and air groups of existing ships so no increase in the number of carrier aircraft was required. The two ships to be ordered in 1940 and completed in 1944 would displace Marlborough which would go into reserve and Ark Royal which would replace Furious as the training ship.
There would be fourteen aircraft carriers consisting of ten ships of the 27,000 ton type and four of the 22,500 ton type because Courageous, Furious and Glorious were to be scrapped. The ten newest ships would be operational warships operating 48 aircraft in four squadrons of 12 aircraft. Ark Royal was in service as the training ship and the other three Benbow class would be in reserve. In wartime eight of the 14 ships would operate with the main fleets, four would operate with the cruiser squadrons on the North America, South Atlantic, East Indies and China Stations, one would be a training ship and fourteenth would be a spare.
The strength of the Naval Aviation would still be the 480 aircraft in 40 squadrons of 12 aircraft that was planned to be reached by 31st March 1941. That was enough to provide the ten operational ships with their air groups. However, the air groups for the Benbow, Emperor of India and Marlborough would not be formed until the Cabinet ordered the mobilisation of the Reserve Fleet.
Costs
The OTL Ark Royal cost £4 million and the TTL Benbow class aught to cost the same. That's an increase of £12 million spent over the seven financial years 1931-32 to 1937-38. The estimated cost of the OTL Illustrious class was £4 million per ship and the 27,000 ton version should cost no more than 25% more or £1 million per ship and a total of £6 million for the six ships that were built ITTL. That's not much more compared to what was being spent on the armed forces after 1936 IOTL. It will also help that the first ship is ordered in the 1935-36 Estimates instead of 1936-37 so the larger sum of money is spent over a greater number of financial years.
There's no increase in the operating costs of the Royal Navy until Benbow is completed in the second half of 1935. The OTL Ark Royal had a crew of 1,600 men so the four extra ships in service in September 1939 (i.e. Benbow, Emperor of India, Marlborough and TTL-Illustrious) mean that the TTL will need another 6,400 men afloat in September 1939 plus the necessary "backing" of men ashore in the maintenance and training establishments ashore. The regular Royal Navy had about 120,000 men (including about 12,000 Royal Marines) at the outbreak of World War II IOTL.
That means that the TTL personnel will approach 130,000 in September 1939, except it will be more than that because there will be more cruisers ITTL as well.