4: Treaty Cruisers


After the Washington Naval Treaty came into effect many navies around the world raced to build a new class of cruisers that fit within the guidelines specified by the treaty. It was a challenge and the results were not always great.


  • Treaty Cruisers: The First International Warship Building Competition by Leo Marriot
  • Warships After Washington: The Development of the Five Major Fleets 1922-1930 by John Jordan

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Hello everyone and welcome to History of the Second World War Members Episode number 4 - The Treaty Cruisers. While the naval limitation treaties which would begin with the one signed in Washington in 1922 would not be in force throughout the entire interwar period they would still have a lasting impact on naval design well into the war years. Until the closing stages of the Pacific War the vast majority of naval ships in all of the navies of the world were either ships that had been constructed before the treaty was in place, ships that were built directly under the constraints of the treaty, or ships whose design was greatly impacted by the years that every nation spent designing around treaty limitations. In most cases these constraints meant that ships had to be built smaller than what probably would have happened otherwise, but there was one type of ship that instead of getting smaller due to the treaty instead got larger, and that type was the cruiser. Trying to categorize and classify cruisers is a bit confusing, there were armored, protected, and light cruisers before the First World War, and after there would be a light and heavy classification. The only real similarity between all cruisers is that they were larger than destroyers but smaller that capital ships. The reason for the wide range of designs and capabilities within that space was that the cruisers were called upon to complete a wide variety of tasks. Trade protection and commerce raiding would become their most publicized role, with the exploits of ships like the German Cruiser Emden during the First World War being front page news. But cruisers were also important utility ships, scouting for the fleet, hunting down enemy destroyers and cruisers, patrolling, and a whole list of other jobs. All of these different roles would lead to many different designs, but then the Washington Naval treaty would be put in place and it contained a very specific set of limits on cruisers. These limits, with a maximum allowable displacement of 10,000 tons and a maximum gun size of 8 inches would cause every major navy in the world to suddenly treat those limitations not as maximums but instead the absolute minimum allowable size for new cruisers. In this episode we will discuss some of the attempts by the major navies of the world to create ships that met these new requirements and discuss the many trade offs that they would be forced to make to try and create their own treaty cruisers.

The inclusion of the 10,000 ton limit in the Washington Treaty was an interesting event because much like the 35,000 ton limit on capital ships it was not really based on any coherent idea of what was the best or correct size of a cruiser, it was instead just a number that was simply a number that was able to accommodate cruisers that were under construction at the time of the conference. The British had just finished building a cruiser, the first of the Hawkins class, which was 10,000 tons with 7.5 inch guns. This class of ships had been built with the commerce protection role in mind, essentially in response to ships like the Emden who had done so well during the war. The Hawkins class was the first of its kind in the Royal Navy, and it would prove to be a problematic design, but those problems would only become apparent later, after the treaty had already used the Hawkins as the template for what a large cruiser should be. The limit, when proposed, was able to gain the support of the American Navy because they wanted to build big cruisers due to the distances that they would likely have to traverse in the Pacific theater. As I mentioned, there was not a ton of thought given to the technical side of such a limit, as described by Stephen Roskill and Corelli Barnett in Naval Policy Between Wars. Volume I: The Period of Anglo-American Antagonism 1919-1929 “A curious feature of this phase of the negotiations is, however, that neither the British nor the American naval authorities appear to have given serious thought to the tactical and technical aspects of the decision that future cruisers could be very much larger than almost all existing ships, and could be armed with an untried weapon of considerably larger calibre. And the virtual certainty that the naval powers would design their new cruisers right up to the permissible limits seems to have passed unnoticed. Thus the conference on naval limitation can reasonably be said to have ensured a substantial increase in the size and armament of one important class of ship.” The fact that these new cruisers would certainly outmatch any currently existing cruisers meant that almost overnight the conference had created another naval arms race, and instead of designing and building capital ships the world’s navies would soon be trying to design and build better Treaty Cruisers.

During the design process for the treaty cruisers there were sacrifices that would have to be made to fit the ships within the available displacement. There were also important considerations given to what other nations were doing with their cruisers. For example one of the features of the ships where it was important to consider other designs was in the area of speed, no nation wanted their ships to be slower than others, and so everybody wanted to make sure their cruisers had the highest possible top speed. Trying to achieve this speed is where sacrifices would have to be made, to make a ship go faster it would need more space and weight dedicated to propulsion systems and with a hard limit on overall ship displacement this weight would have to be reduced in other areas. With the equally strong desire to make sure that the largest possible guns were used, 8 inches in diameter, the only place where weight could be saved was in the armor. For a long time the tradition had been to create balanced ships, which meant they were designed around the idea that they should have enough armor to match the shells of a ship using the same caliber of guns. With the tight displacement limitations this arrangement was simply not possible with the treaty cruisers, there just was not enough available tonnage to fit everything that was required and so the first generation of treaty cruisers, while mounting 8 inch guns, would have armor protection that was barely sufficient to protect against guns smaller than 6 inches which were at the time found on most destroyers. Trying to somehow fit all of these requirements into a very small package would be the theme for each of the navies as they tried to develop their own classes of treaty cruisers.

Due to the fact that the British had been the cause for the 10,000 ton limit in the first place, we will start our trip around the world with the Royal Navy. After the treaty was put in place the first generation of designs for the Royal Navy involved a cruiser with 8 8 inch guns mounted in four twin turrets, with two fore and two aft of the superstructure. These guns were mounted in high angle turrets, which theoretically capable of being used in an anti-aircraft role, although much like other high angle turrets designed by the Royal Navy during this period they were full of challenges and problems. Most of these issues revolved around the difficulty of creating and operating turrets efficiently while also giving them the ability to shoot at high angles. Within the design limits the main armament was provided with 100 rounds per gun, although this was later increased to up to 150 due to weight reductions in later refits, however these were the design limitations for how many rounds could be carried, not the actual limits which were much higher during the war. There were also dual purpose 4 inch guns as well as dedicated anti aircraft mounts meant for quadruple 2 pound AA guns, although these were still under development at the time and so they would only be mounted later. The initial goal was to allow the ships to reach a top speed of 33 knots, however this proved to be challenging due to the weight limitations and the amount of horsepower required for every additional knot of speed. Therefore a top speed of 31 knots was eventually settled on because this could be achieved with 75,000 knots instead of the 100,000 horsepower required for 33 knots, which resulted in a weight savings of 400 tons. After these designs were accepted by the Navy the plan was to begin a large building program that would eventually result in the Royal Navy having 17 of these treaty cruisers, which were known as the County Class, and they planned to start off big with 8 laid down in 1924. It was at this point that the political realities of the time altered these plans. A Labour government was elected in 1924 with the goal of spending less on the military, including the navy, and therefore the planned number of cruisers was cut in half, although 5 were still laid down in 1924. One of the challenges that the Royal Navy was running into was that these new treaty cruisers were much more expensive than the ships that they were replacing, and the requirements of the worldwide trade network of the Empire did not really allow the navy to reduce the number of ships total. In hindsight it almost certainly would have been better for the British to have advocated for a smaller ship displacement at Washington, even if it meant sacrificing the Hawkins class, so that it would have been cheaper to build the number of cruisers that were required by the Royal Navy. However, this was not the path that they were on, and so instead they would try to evolve and improve the design of the treaty cruisers in future iterations.

While the first set of County class cruisers were just starting construction, which would be called the Kent-class, the plans for the next, the London-class were already being refined. There were changes to the basic design almost immediately, like a slight increase in the overall length of the ships and a reduction in the overall width which allowed for a slight increase in speed. However, most of these changes were small changes that produced slightly different performance profiles but did not in anyway alter the general characteristics of the ships. The same was true for the final two ships of the County class which would be laid down in 1927. More ships were planned but economic realities put those plans first on hold, and the finally they were cancelled. While the number was much smaller that they hoped the Royal Navy was still able to produce 11 Treaty cruisers either in commission or nearing completion at the end of 1930, which was far more than the United States. The Royal Navy also began planning for the future, with plans for a new class of heavy cruisers to be constructed after the treaty limitations were no longer in place, which by the early 1930s looked to be a question of when and not if. If built they would have been closer to 20,000 tons instead of 10,000, with almost four times the amount of armored protection. This would have put them roughly on par with some pre-world war 1 battleships which had participated in the Battle of Jutland. However, these larger cruisers would never make it off the drawing boards before the beginning of the war, at which point they were abandoned to allow greater focus on more important concerns.

While the Royal Navy had started to design treaty cruisers immediately after the conference and had then started construction in 1924, the United States would be more delayed. This meant that the first treaty cruiser for the United States Navy was not laid down until 1926, although the United States would eventually build more Treaty and Heavy cruisers than any other nation. The resulting class of ships, named the Pensacola class, would be heavily influenced by the British Hawkins class and much like almost every other treaty cruiser it was designed right up to the displacement limit. The Pensacola’s would mount more guns than the British ships, with 10 instead of 8 8-inch guns. These guns would be configured in what I think is a unique arrangement, with 2 double and 2 triple turrets, but with the triple turrets mounted above the doubles, instead of the more typical opposite. This arrangement was put in place because the width of the hull would not accommodate the width of the triple turret as far forward as it would need to be. These initial ships had a very light complement of anti-aircraft guns, although this would be greatly improved in later refits. While the British had focused their design on the needs of trade protection the United States would put far greater emphasis on the scouting ability of their cruisers, and with aircraft being so potent in this role the Pensacolas would be given an initial complement of 4 seaplanes that could be launched from the ship’s two catapults. The final displacements of these ships was only 9,100 tons, well under the treaty limit due to the absolute barebones nature of their protective armor, a feature which was seen as a mistake soon after the ships were completed. Eventually only 2 Pensacola class ships would be built, both in 1925, and future ships would be of an enhanced design.

The next class of treaty cruisers would reduce the number of guns down to 9, with the decision made based on the actions of foreign navies. The idea was that, with most other nations opting for only mounting 8 inch guns, the United States could subtract one gun to save some weight for use on other items. These 9 guns were mounted in 3 triple turrets, which still gave some superiority of fire, but did not necessitate a fourth turret and the weight and design restrictions that 4 turrets entailed. This change would first appear in the Northampton class which was laid down in 1928. The switch to a three turret layout also provided more space for aircraft facilities aboard ship, which satisfied the desire to ensure that the ships were potent fleet scouts. The Northamptons would incorporate the largest changes that would be made on the American side of treaty cruiser design. Future classes, like the Portland and New Orleans class contained evolutionary changes, but nothing truly revolutionary. The most important change would come in the New Orleans when the extra weight which had not been used in previous treaty cruisers was utilized by increasing the amount of armor provided. By the time that the New Orleans class was launched in the mid 30s, the amount of armor being provided for American treaty cruisers had doubled. The last Treaty cruiser built by the United States, the USS Wichita, would leave the Navy with 18 heavy cruisers, which was all that could be built under the confines of the treaty which was altered at the London Naval Conference in 1930 to put an upper limit on the total cruiser tonnage that the navies could posses. The next class of United States heavy cruisers would no longer obey the treaty restrictions, with the Baltimore class displacing 14,000 tons.

While the Baltimore ships would not fall under the category of treaty cruisers, given their relation to the previous cruisers they are still worth discussing. Unlike some other nations, which basically stopped making heavy cruisers when the treaty lapsed, the United States would really double down on their construction for use in the Pacific. 24 Baltimore class ships were orders, although only 18 would actually be completed before the end of the war, with only 6 arriving in time to see meaningful action. There were then plans for a Des Moines class of ships, of which there would have been 12, but only 3 were completed. By the time that these final ships were being constructed in the final stages of the war their armament had shifted, and while they still mounted the same number of large guns, the anti-aircraft armament on each ship had exploded in number. It should also probably be mentioned that while the numbers of ships under construction for the US Navy seem incredibly large near the end of the war, this was partially due to the fact that in 1945 the Americans were building a colossal number of ships of all types, most of which would not be completed before the war ended. The last of the Des Moines class, the Newport News, would be de-commissioned in 1975, making it the last of the treaty influenced heavy cruisers that mounted the 8 inch guns in active service.

For Japan the treaty Cruisers maintained a special place within naval plans because they were the largest ships which were not limited by the treaty. This meant that the Japanese could theoretically build as many treaty cruisers as they wanted, at least under the initial treaty and so they saw this ship as a way to at least somewhat offset the disadvantage that they were forced to accept in capital ships. The first set of designs were the Myoko class and they, like the American ships mounted 10 8 inch guns in 5 double turrets. The Japanese would claim that this all fit within the 10,000 ton displacement limit, but the actual displacement was probably closer to 11,000 tons. All four of the Myoko cruisers would be completed by 1928, at which point work began on the Takao class, which was just an evolutionary design on the Myoko. There were soon plans for another class of ships, but then the London Naval Conference occurred and the cap on heavy cruisers meant that Japan was already at its limit with the 12 ships that it already had either in commission or nearing completion. While technically this prevented further Japanese treaty cruisers, they were able to get around this a bit by continuing to build “light” cruisers which had a tonnage limitation of 8,500. This would result in the Mogami class which mounted 6 inch guns, the maximum allowable for the type, but there would be a total of 15 of them. The Mogami’s would also mount 4 triple torpedo tubes, which was the standard torpedo setup for all Japanese Treaty cruisers. Trying to fit all of this into 8,500 tons was pretty much impossible, and the standard displacement of the Mogami’s was much closer to the 10,000 limit for treaty cruisers. There would be some design issues with the Mogamis, mostly revolving around stability at sea and some issues with the welding on the hull and this would cause a series of necessary modifications to be made to the first two ships after they were completed, and to the final two ships while they were still under construction. These alterations led to a further increase in displacement. After Japan exited the Washington Treaty they would build the Tone class of heavy cruisers which had a displacement well above 10,000 tons. These ships would mount only 8 8 inch guns, but they were all mounted in front of the superstructure, with the areas behind the super structure devoted solely to aircraft operations. This allowed for 6 floatplanes to be carried for use by the ship. There were plans for another class of cruisers, the Ibuki class, which would have been an even larger cruiser based on the Mogami design, but they were not completed. The Ibuki would not be launched until May 1943, but at that point construction was put on hold while attempts were made to turn the ship into an aircraft carrier, work that was not completed.

While the three largest navies would produce the largest numbers of treaty cruisers, other nations would also join in their design and construction, just in smaller numbers. For the Italians the first set of treaty cruisers would belong to the Trento class, of which 2 would be built starting in 1925. They would have a pretty standard armament with 8 8 inch guns in twin turrets. The Italians had some advantages over the big three navies in that, with their position in the Mediterranean, overall range and endurance for their ships was far less important. Instead they emphasized speed and the Trento class had a design speed of above 35 knots. This would be achieved by forgoing armor almost entirely so that more weight and space could be devoted to propulsion machinery. In the next class, the Zara class, there was some pullback on this, and the top speed would be set at just 29 knots. This allowed for the ships to be shorter, and after the torpedo armament was removed and the complement of aircraft reduced to two, about 1,500 tons was freed up to dedicate to protection. However, even with all of the efforts to save weight the final displacement would still be well over 11,000 tons.

The French were in a similar position, they put a much smaller emphasis on range, with their first set of treaty cruisers, the Suffren class, having close to half the range of their British counterparts. However, a top speed of 35 knots was recorded during trials and unlike the Italian cruisers, the French were also able to use a hull design which retained more of that top speed when the ship was fully loaded. The Italian Trento class generally lost over 6 knots when fully loaded, whereas the French were able to keep their speed at above 30 knots. These French ships also put much greater emphasis on torpedo armament when compared to their European counterparts with the ships mounting 12 torpedo tubes in four triple turrets. In 1930 the first of the next generation of French treaty cruisers was laid down, the Algerie with one of the new design requirement for the ship being protection from at least 6 inch guns which were starting to be mounted on more and more Italian ships during this period. This meant that more weight had to be devoted to armor. One of the major changes that allowed this to happen was a reduction both in machinery weight, 275 tons, but also a large reduction in machinery size which required a much smaller armored area for protection. There is a school of thought that the Algerie was probably the best treaty cruiser to be built, and assertion that is difficult to prove in any meaningful way under the best circumstances, but especially with the French ships due to their very small operational history before being scuttled with the rest of the French fleet in 1942.

The final navy that built something like a treaty cruiser was the German Navy, technically their answer to the treaty cruisers being built by other nations were not actually treaty cruisers, but panzerschiffe, or armoured ship, in what would be called the Deutschland class. The three ships of this class would at least publicly obey some of the limits placed on treaty cruisers, like the 10,000 on displacement limit, but they would mount 6 11 inch guns within that weight. Just like several other navies, these ships were not actually within the 10,000 ton limit, and they went over by several hundred ton, but with so many nations also playing a bit fast and loose with actual displacement numbers, it is hard to blame the Germans for this problem. The Deutschland class would be unique in that they would be propelled by diesel engines, which provided savings in weight, size, and endurance. This allowed the ships to have almost twice the range as their contemporary British counterparts. The diesels were considered so successful that there was a strong push to use them in the next set of German cruisers, the Admiral Hipper Class, which came in at 14,000 ton, and there was even debate about the possibility of using them on the Bismarck class battleships. The exploits of at least one of these panzerschiffe will be discussed in much greater detail in later episodes.