…The London Naval Treaty shifted the focus of naval competition from capital ships to large cruisers and aircraft carriers. The United States, with 6 ships of the Louisville class well underway had the advantage there. A pair of repeat Louisville’s with an extra pair of AAA guns, the New Orleans class, were ordered in 1923. In 1924, thanks to early reports of the Japanese Ashigara class with 10 8” guns the San Francisco class was ordered. These ships dropped the torpedo tubes, 1 knot of speed and reduced their immune zone against 8” fire in exchange for increasing the main battery to 12 8” guns in 4 triple turrets. The follow on Tuscaloosa class of 1925 reduced the armament to 2 twins and 2 triples to increase the armor after reports that the Japanese 8” cruisers used a new 50 caliber gun rather than the old 45 caliber gun as previously believed. This was followed by the Brooklyn class of 1926 that further increased armor, but reduced the main battery to 9 guns in 3 triple turrets, setting a pattern for further US large cruisers…
…Japanese plans for their large cruiser force called for 18 ships, 4 would be the nominally 8,000 ton Minase class already building, 4 would be 12,500 ton designs as squadron flagships and the remaining 10 would be nominally 9300 ton vessels, using up the 175,000 tons allotted to Japan. The Japanese were planning on lying to a moderate degree, their 9300 ton vessels would be 11,000 tons in actuality as planned, if caught they would merely cancel the last of the vessels.
The plan was to lay down the first two of the six 11,000 ton Ashigaras in 1924, but funding problems from the Great Kanto Earthquake pushed things back to 1925. These ships were to be capable of 35 knots, carry 10 8” guns in 5 twin turrets and 12 24” torpedo tubes in fixed single mounts. They were to serve as both heavy scouts and heavy torpedo attack platforms that could ignore battleship secondaries. In practice the ships ended up completed at 13,000 tons due to Japanese inability to accurately compute ships weights, and lacking in structural strength as well. These changes led to the second pair being declared at 10,500 tons as the Aoba class and the third pair at 12,000 tons as the Nachi class, while actually displacing 13,500 and 14,000 tons respectively due to added structural reinforcements. These changes led to the last two large cruisers of the program being cancelled and the second to last pair being replanned as additional 12,500 ton flagship units…
…The British intended to build 23 large cruisers, 8 12,500 ton designs and 15 10,000 ton designs, which would give them the ability to match France or Italy in maximum size cruisers, and outmatch the planned number of Japanese cruisers of such size. This soon shifted to 8 12,500 ton designs for the RN, 10 10,000 ton designs for the RN and 4 12,500 ton designs for the RAN, as Australia asked for permission to build some of their own to replace the scrapped Battlecruiser Australia. The RN designs were fairly orthodox, with 4x2 8” guns , 8 21” torpedo tubes and 32 knots of speed, the 12,500 ton ships differing in being very well armored as opposed to just well armored, an extra float plane and having 4.7” as opposed to 4” AA guns. The Australian ships were domestic ships, designed and built at Cockatoo Island dockyard. They were capable of similar speed to the British counterparts and were slightly better armored, but had their main battery in a 3x3 arrangement, and five pairs of 4” AA guns, one of which was superfiring over the rear turret…
…France planned for 8 12,500 ton large to fill their complement. Their design with the Duquense class was a 35 knot ship with 4 twin 8” guns, 10 75mm AA guns and 8 550mm torpedo tubes. The early French design lacked armor however, due to a French deficiency in metallurgy and the addition of a small set of coal fired cruising boilers, resulting in it being the most poorly armored of the large cruisers, with a belt of only 45mm…
…Like France Italy planned to fill its complement of large cruisers with 8 12,500 ton designs. Unlike the French they planned on outright lying and building 13,500 ton ships. These vessels were 35 knot ships, with an orthodox 4x2 8” armament, a heavy armament of 8x2 100mm guns, 12 21” torpedo tubes and heavy armor, made possible both by cheating and by having a very short range….
…Spain, facing financial difficulties from the Rif War even after it ended decided to postpone any large cruiser construction until the 30’s…
…With the conversion of the battlecruisers Ironsides and United States into aircraft carriers still incomplete the United States was looking at their fifth vessel. However exact opinions varied on what it should look like with different features being floated. Rather than tie down some of their limited tonnage in a vessel that was semi experimental it was decided to build a ship small enough to fit under unlimited cruiser tonnage. Given the difficulties in fitting a powerplant to reach 33 knots on a 10,000 ton hull and still have useful volume, it was decided that the experimental ship, tentatively named Bunker Hill, would be a 27 knot design. While too slow to operate with the large carriers under conversion, it would be able to support the battle line with scouts, fighters for defense and spotter aircraft, giving the opportunity to remove floatplanes and their flammable stores from the battleships. She would test an islandless configuration that the aviators insisted would be better for flight operations…
…Britain found herself with four carriers that she soon determined were too small for her needs. In 1925 she sought to rectify this with a pair of 22,500 ton ships. They would have a speed of 30 knots, room for 60 aircraft, 8 8” guns for defense in single mounts and 12 4” AA guns, along with moderate protection over the magazines and machinery. Further ships would be ordered in 1929 and 1933 respectively, with a final 15,000 ton maintenance and support carrier to fill their tonnage quota in 1935…
…Japan found herself continuing with the construction of 32 knot 30,000 ton vessels based on the machinery from the cancelled Kii class battleships. Based on negative experience with the islandless Eisho both vessels were constructed with an island. They fitted 10 8” guns for self-defense in six single mounts and two twin turrets and had triple level flight decks for rapid launching of their 80 plane complements…
…France originally planned on converting the incomplete battleship Bearn into a carrier, but soon found that by the time money was available the hull had decayed too much. Instead it was decided to build a small carrier on a Duguay-Trouin light cruiser hull as an experimental vessel…
…Italy saw they had no money for an aircraft carrier, and instead converted a train ferry into a seaplane tender for colonial use. Otherwise it was assumed their fleet would be operating sufficiently close to home that land based air would suffice…
…Spain was content with their current seaplane tender and saw no need for further aviation vessels in the 20’s…
…The most significant event in naval aviation in the early 20’s were the Project B tests off the Atlantic coast. Nominally commanded by James Fechet, most of the actual work was done by his chief of staff Quentin Roosevelt given Fechet’s other responsibilities. The Project B tests saw five predreadnought and two dreadnought battleships systematically sunk alongside numerous smaller vessels by aerial bombardment in a measured manner. The vessels were sunk over multiple days with time taken to examine the damage from each wave of bombs and torpedoes by a party of naval engineers.
Further tests were conducted against two radio controlled naval target ships to determine practical hit rates in combat. Roosevelt innovated here by having the target ships rigged with fireworks set to distract pilots and simulate gunfire. He further included defending and escort fighters to the mix in various tests.
As a result of these tests it was determined that against post Jutland capital ships AP bombs of at least 1500 pounds were necessary, with 2000 being desired, though smaller weapons would suffice against cruisers and older capital ships. For torpedoes a 21” weapon was judged necessary to be effective against the defenses of Post Jutland capital ships, which would require a larger torpedo bomber to carry it, though the present 18” weapon was sufficient against older vessels. Based on this it was determined that at least 60 level bombers or 30 torpedo bombers were needed to engage a modern capital ship without air cover to sink it…
…The most important naval war prize from Germany was the incomplete radar system that they were working on. While a long way from being deployable by the time the war ended, the system promised the ability to detect ships in complete darkness or heavy fog at 10,000 yards. Both the United States and Britain received copies of the development notes, with the Japanese getting their second hand from Britain via espionage, and all three began working on their own systems by the end of 1920. By 1930 all three had crude first generation devices in testing at sea…
…The Geneva Naval Conference of 1926 occurred as mandated by the London Naval Treaty. The Conference goal was to further reduce naval expenditure. The primary British goal was to try and further reduce the tonnage allotted to first class cruisers to 150,000 tons for the US and UK, 100,000 for Japan and 67,500 for France and Italy. A second goal was to create a restricted second class cruiser class, in order to prevent the construction of large numbers of 10,000 ton 6” armed cruisers the United States and Japan planned on constructing. To complement these would be an unlimited type of cruiser of 6” armament and no more than 7500 tons. A final goal was to see about if Aircraft carrier tonnage could be reduced.
The American goal was to establish tonnage limits for light cruisers, destroyers and submarines. This would allow the US to avoid a naval race with Japan in lighter categories of warship. The current tonnage limits satisfied the United States and were to be retained at all costs.
The agendas of the other powers soon proved irrelevant as the differences between the United States and United Kingdom proved insoluble. The United Kingdom would agree to a light cruiser limit in addition to retaining current limitations, and were willing to accept parity with the US, but they insisted on no less than 450,000 tons as the allotment for light cruisers. The United States by contrast proposed an allotment of 250,000 tons. The United States would compromise on no more than 300,000 tons, the United Kingdom no less than 375,000. A British counter proposal of accepting the American 250,000 ton proposal and placing the destroyer limit at 3500 tons with an unlimited allotment was thrown out as blatantly against the spirit of limiting cruisers.
Attempts to salvage something in the conference by limiting submarines failed. Both the United States and French were too interested in building large submarines, to operate off Japan from San Diego in the former case, and as global commerce raiders in the latter case, for there to be an agreement on submarine size limits. Similarly without a size limit tonnage limitations proved too difficult to devise. This left the conference as a complete failure…
… In 1927 the British laid down a pair of Beatty class Battlecruisers as their fifth and sixth ship under the LNT, functionally variants of the Venerable class Battleship, itself a modified N4 to comply with the LNT. The Beatty class reduced the unique quad turret at the rear of the Venerable to another triple, thinned the armor and increased speed to 29 knots. The ships were right on 45,000 tons as opposed to being just above 43,000 thanks to greater experience with the weight savings used...
…The Brazilians ordered their fourth battleship in 1924. Both the British and Americans competed for the contract, the British offering a lower absolute price and faster delivery, while the Americans offered better payment terms. It was the latter that proved decisive in winning the contract for the Americans, even if they had to use British 15” export guns. The Riachuelo was a 35,000 ton ships with 3x3 15”/45 Vickers export guns mounted all forward and a speed of 28 knots, along with good armor and 12 6” secondary guns. This was bought alongside two modified New Orleans class Heavy cruisers. As a consolation British yards won a contract for a 6” armed training cruiser…
…Argentina responded to the Brazilian heavy cruiser purchase by purchasing three of their own. The Italians managed to win the contract, most likely through bribery, and responded with cut down versions of their Pola class cruiser. These vessels used a smaller 7.5” main battery of British guns, 12 as opposed to 16 secondary guns, half the torpedo tubes, less armor and 3 knots less speed…
…Chile saw no ability to match her neighbors buildup and contented herself with a single light cruiser for cadet training, a near sister of the Brazilian vessel…
…Japanese naval cooperation with the Soviet Union was substantially more limited and of a more mercenary bent than Germany’s land and air based cooperation. Unbeknownst to the world at large the agreement to trade Northern Sakhalin for the return of the former White Pacific Fleet, seized by the Japanese for nonpayment of docking fees, had a secret component. There Japan proposed to sell armor plate, boilers and turbines to complete Izmail, Borodino and Kinburn in exchange for gold, and a set of 16” guns and turrets for Borodino. This would allow the Red Navy two battlecruisers and an aircraft carrier while giving Japanese naval industry additional work…
…In 1925 German naval cooperation with the Dutch had an odd result. The Dutch had contemplated an ambitious naval expansion plan before WWI involving 4 to 9 battleships, that the war had reduced to a mere trio of light cruisers. Attempts to acquire units of the HSF either driven ashore or forced to intern during the battle of the Eastern Approaches proved unfruitful. This left them in a relatively weak position. The reason they had desired to acquire capital ships was for the defense of the Netherlands East Indies, namely ensuring its neutrality in a conflict between Japan and either the United States or the United Kingdom by being strong enough to crush a Japanese probe. The war made it impossible for them to procure capital ships and this forced a less ambitious goal. They would order a set of light cruisers that would be potent enough to defeat Japanese scouting units, trusting that Japan would keep her capital ships reserved for fighting the US or UK.
By 1925 it was clear that the Java class cruisers, with only unturreted 10 5.9” guns were no match for the Japanese heavy cruisers under construction. This would mean that the Japanese scouting units would soon be able to defeat the defenders of the NEI with impunity. This made maintaining neutrality a much trickier thing for the Dutch. Something larger was needed. However the Dutch Navy was well aware that it would take time for the politicians to determine what they were going to procure. A relatively small battleship of 30,000 tons? A similarly sized battlecruiser? A 20,000 ton cruiser killer? 12,500 ton heavy cruisers of their own? In order to get something the Dutch Navy wanted a single unit of a stopgap design, similar to the role played by the old coastal defense ship De Zeven Provincen.
At the same time Germany was in final design studies for what would become the first of the “Armored Ships” they were allowed under the Treaty of Versailles. After debating between a larger than average 8” cruiser or a 15” armed super coastal defense ship the Germans had decided on a compromise design with 11” guns. Slower than most cruisers at 29 knots, it was well armed with 6 11” guns in two triple turrets, four twin 6” guns and two quad 21” torpedo launchers. Use of welding saved enough weight for it to be almost immune to 8” gunfire at expected battle ranges and diesel engines gave it phenomenal range. Of course the Germans were planning on lying about the displacement by at least 2,000 tons as well to give them more margin. Given the small size of the German ship design office it was inevitable that someone in the know about this project was working with the Dutch in their clandestine submarine development program in the Netherlands.
The German “Armored Ship” design was basically exactly what the Dutch were looking for. It was small enough that they had a reasonable chance of getting it past parliament, while powerful enough to make any Japanese heavy cruiser regret tangling with it. If the Japanese did send a capital ship to deal with it, then that put the ship within reach of Dutch submarines and minefields, exposing it to a potential loss and being something the Japanese Navy would have to consider if they wanted to violate Dutch neutrality.
Of course the German design would need some adjustments to fit Dutch needs. Swedish guns would be substituted for German to get around Versailles export restrictions. The experimental diesel plant would be replaced with a steam plant, allowing 31 knots to outrun Japanese battlecruisers at the cost of range being reduced from insane to more than adequate for Dutch needs. And of course it would have to actually be 15,000 tons, so nobody asked any awkward questions when the Germans built their ships…
-Excerpt from Naval History Between the Wars, Harper & Brothers, New York, 2007