Developing The World's Most Powerful Heavy Cruiser: IJN Efforts and Successes

Developing The World's Most Powerful Heavy Cruiser: IJN Efforts and Successes
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From Feudalism to World Power in A Few Decades

Japan is unique among Asian countries in that it is both an island and remained un-colonized during the 19th Century. However, its position as an outlier in Asia susceptible to attacks from the sea also meant that Japan entered the 20th Century extremely cognizant of its military vulnerability relative to the modern European powers. From its forced opening to international trade by Commodore Perry in the late 1800s Japan was roiled by a perpetual fear of being colonized and subjugated in the manner of China.

It embarked on a crash program of modernization and industrialization, and performed a miracle of economic transformation unlike any other in world history. Driven by a policy that brought a push for a strong military and strong economy to preserve Japan’s independence, the Imperial Japanese Navy grew by leaps and bounds from its inception.

And it was not long before it was sent to prove itself by fire. In 1906 the Japanese Navy won a significant victory over a Russian fleet during the Russo-Japanese war, and in doing so announced to the world that it was a force to be reckoned with. The development of modern warships was largely inspired by Britain’s Royal Navy, and by the First World War Japan fielded several classes of modern, capable warships that helped it seize German colonies in the Pacific.

One of the last of these, the class led by the IJN heavy cruiser Chikuma, was in fact not a heavy cruiser at all, but a set of protected cruisers that would give birth to the post Washington Naval Treaty breeds of light and heavy cruisers.

Developing The Most Powerful Heavy Cruisers in the World

Due to its late industrialization process, Japan imported many established ideas and practices from the developed world. This allowed Japan to avoid making costly mistakes in both domestic and military production. For example, Japan’s Navy did not invest heavily in lightly armored battlecruisers, which the First World War had shown were prone to catastrophic explosions when struck near their ammunition stowage.

This jump start contributed to Japan’s taking the lead in the development of several classes of cutting edge warships during the Interwar period between 1918 and 1939. The IJN heavy cruiser Chikuma (or protected cruiser to be precise) class was succeeded by a series of heavy cruisers that grew increasingly powerful with each passing year. In the 1920s the old style of having single guns scattered about the cruiser’s deck was abandoned in favor of concentrating firepower in twin and multiple gun turrets along the centerline of the vessel. Armor was increased to provide protection against other cruisers, and anti-torpedo bulges were added to protect against that emerging threat. And weapons systems began to be tied to fire control directors that radically increased the accuracy of naval guns in combat.

Several classes were built of ever more powerful heavy cruisers. IJN theorists began to plan for war with major powers like the United Kingdom or United States, which in any conceivable scenario would possess more warships than Japan could hope to build and maintain. This led planners to conclude that quality would have to be upped in all warship designs to counteract the advantages provided by quantity.

The IJN heavy cruiser Myoko was the lead vessel of a four ship class that, when launched in the late 1920’s held the distinction of being the most powerful heavy cruisers in the world. In fact, the only cruisers to directly supersede the Myoko and her sisters in terms of armament were later Japanese heavy cruiser designs, and this would lead to major repercussions come the start of the Second World War.

The Myoko Class: Setting the Standard

The Myoko was unique in carrying a full ten guns in five twin turrets as her main armament. These guns measured 7.9 inches in diameter and gave Myoko a massive broadside for a heavy cruiser. To this offensive punch was added a full twelve torpedo tubes in four triple mounts which could eventually launch the famous and feared “Long Lance” torpedo - a weapon that could strike enemy warships miles distant and without warning.

The Myoko class was powerful in other respects as well. They could dash at speeds up to 35 knots, and carried floatplanes to act as scouts and gunnery supports. Almost 800 sailors crewed the ships, and they displaced upwards of 15,000 tons when fully loaded for combat. Indeed, not only were they the most powerful cruisers of their time they were some of the largest until the 1940s saw heavy cruisers pushing 20,000 ton displacements on a regular basis.

IJN heavy cruiser Myoko cannot be said to have caused panic upon her launch, but she definitely concerned US and UK naval planners. Her broadside was particularly concerning: most western cruisers were built with six or eight guns at the most. Myoko threatened to outclass them all, and planners hastily began putting together designs meant to counter her.

In truth the Japanese superiority in heavy cruisers was never fully mitigated - but not only because of their heavy gun armament. As the Pacific Theater of World War II would show, the torpedoes were to pose as much of a threat as the guns in the frantic battles off Guadalcanal and Alaska. Heavy cruiser engagements were often quite one sided.

IJN Heavy Cruisers at War: Myoko and the new Chikuma

The old protected cruiser Chikuma was not the last warship to bear that name. One of the last heavy cruisers ever built by Japan was a further development of the standard set by Myoko and also carried the name Chikuma. IJN heavy cruiser Chikuma would fight, as would Myoko, in some of the fiercest naval engagements of the Second World War.

Myoko demonstrated her prowess in the Battle of the Java Sea in 1942. This battle, really a series of naval engagements off modern day Indonesia, destroyed the last Allied naval force in the western Pacific with virtually no loss to the Japanese. During a series of engagements the Dutch light cruisers De Ruyter and Java were sunk, the Australians lost light cruiser HMS Perth, the Royal Navy lost heavy cruiser HMS Exeter - a veteran of the battle to destroy the Graf Spee - and the US Navy lost the heavy cruiser USS Houston.

Chikuma’s war movements took her from the Indian Ocean all the way up to Alaska. Heavy cruiser groups dueled off the Aleutian Islands during the Japanese occupation of Kiska and Attu during the war, and Chikuma was used on at least one occasion to patrol the area. But her primary contribution came during one of the many naval battles around Guadalcanal, when her scout plane spotted the American carrier USS Enterprise and vectored an air attack onto her. This attack nearly destroyed the American ship and put her out of action for a spell.

Chikuma and Myoko both fought in numerous battles both as part of cruiser divisions and as escorts to carriers. Both suffered significant damage that was repaired in time for them to participate in the 1944 battles over the Philippines. And here both met their fates. Chikuma was hit by torpedoes during the Battle of Leyte Gulf and sank. Myoko was hit by a torpedo fired from a submarine and had to be towed back to Singapore where she spent the remainder of the war as a floating anti-aircraft battery, since no supplies were available to repair her.

But although these ships were lost in the end, they represent major contributions by Japan’s advanced heavy cruisers to her war effort.

IJN Heavy Cruisers At War: Verdict

Japan’s heavy cruisers, in the end, could not change the course of the Pacific War. However as a collective expression of Japanese ingenuity and technological sophistication they are nigh peerless - only equaled by the Yamato Class battleships and the ill-fated carrier IJN Shinano. They fought with distinction and generally outclassed their Allied counterparts. This was due in part to doctrine, and in part to the skill and dedication of Japanese naval personnel, but also the sophistication inherent in Japanese cruiser design.

Interestingly enough, the massive gun armament of Japan’s heavy cruisers was probably less decisive than the massive complement of long range torpedoes. Allied officers took until 1943 to recognize that when ships would explode without warning when still fifteen miles from Japanese surface ships that mines or submarines were not to blame: it was torpedoes that were doing them in. Capable of effectively striking ships fifteen miles away, the torpedoes mounted on Japanese heavy cruisers provided a lethal punch that would confuse opposing formations. After confusion set in, gunfire would do the rest. This pattern held in many of the engagements off the Solomons, and especially the Battle of Savo Island, where Japanese cruisers destroyed four Allied cruisers at no loss to themselves.



  • Janes Fighting Ships of World War II, 1946 Janes Publishing Company, 1994 reprint edition
  • Steve Ewing, American Cruisers of World War II, 1984 Pictoral Histories Publishing Company
  • Arthur Zich, The Rising Sun, 1977 Time Life Books
  • Churchill, The Second World War, 1959 Time Life
  • Images courtesy (respectively) of the Government of Japan, the Government of the United Kingdom, and the Government of the United States.  All accessed via Wiki Commons