This article summarizes the history of the Japanese heavy cruiser Myōkō (妙高), named after Mount Myōkō in Niigata Prefecture, focusing on its development and service with the Imperial Japanese Navy during the Second World War. Designed just months after the Washington Naval Conference of February 1922, the Myōkō-class cruisers were the first built to comply with treaty-imposed limitations. Among the four ships in her class, Myōkō was the first to be laid down. Commissioned in 1929, she took part in nearly all major engagements of the Pacific Theatre during World War II until her scuttling in 1946.
Development and Construction
With the signing of the Washington Naval Treaty in February 1922, all major naval powers agreed to limit cruisers to a displacement of 10,000 tons and a main armament of 8-inch guns. Rear Admiral Hiraga Yuzuru, a distinguished naval architect who designed many of Japan’s warships during the Second World War, was tasked with developing a new class of heavy "treaty" cruisers.
By late 1922, the initial design called for eight 20 cm guns in centerline twin turrets, four 12 cm high-angle guns in single mounts, and eight fixed twin-mounted 61 cm Type 8 torpedo tubes. The ships were also designed to have armor protection against 8-inch shellfire in vital areas, anti-torpedo bulges, a top speed of 35.5 knots, a range of 10,000 nautical miles at 13.5 knots, and provisions for two seaplanes.
At Hiraga’s request, the specifications were later revised to include an additional pair of 20 cm guns, bulkheads within the anti-torpedo bulges, and a reduced range of 8,000 nautical miles at 13.5 knots. The torpedo armament was also removed. The final design was approved on August 25, 1923, and construction orders were issued the same day.
Between November 1923 and August 1924, Hiraga was abroad in the United States. In his absence, the Torpedo Branch of the Naval Technical Department persuaded the Naval General Staff to reinstate torpedo armament for the new heavy cruiser design. Initially planned with eight Type 12 torpedo tubes in twin mounts, the armament was increased to twelve tubes in triple mounts by 1925. Additionally, the number of high-angle guns was raised from four to six.
These modifications added 500 tons to the design's displacement, bringing it to 12,350 tons. Meanwhile, the Great Kantō Earthquake of September 1923 damaged dockyard facilities, delaying construction. Myōkō was laid down on October 25, 1924, launched on April 16, 1927, and completed by the end of July 1929—several months after her sister ships Nachi and Haguro.
After the ships were completed, they were found to exceed their designed displacement by 985 tons. While the additional high-angle guns and torpedo tubes added in 1925 accounted for some of this excess, Japanese sources do not fully explain the remaining weight increase.
The final armament of the Myōkō-class consisted of ten 20 cm guns in twin turrets, six 12 cm high-angle guns in single mounts, two 7.7 mm machine guns, and twelve fixed 61 cm Type 12 torpedo tubes in triple mounts. To achieve the required speed of 35.5 knots, the propulsion system was based on that of the Amagi-class battlecruiser, with four turbine sets generating 131,200 SHP at 210 rpm.
The ships were originally designed for a crew of 704, but armament modifications in 1925 increased this to 764, with the actual complement reaching 792 in service.
Pre-War Service
Initially assigned to Kure Naval Station, Myōkō's homeport was moved to Sasebo on November 15, 1934, where it remained until the end of the war. Along with her sister ships, Myōkō served in the Fourth Squadron (Sentai 4) of the Second Fleet, participating in multiple exercises between 1930 and 1931.
When conflict escalated in China in early 1932, Sentai 4 assisted in transporting Imperial Japanese Army units to Shanghai. In August and September of that year, the squadron conducted gunnery trials and additional exercises. At the end of 1932, the four Myōkō-class cruisers were placed in reserve, replaced in Sentai 4 by the newly completed Takao-class cruisers.
After participating in another exercise in August 1933 as part of Sentai 5, all four ships were reassigned to port guard squadrons in preparation for major modifications in 1934.
Modifications
Plans to modernize the Myōkō-class cruisers were developed in 1931. The existing 20 cm Type 3 Mark I guns were to be replaced with the newer 20.3 cm Type 3 Mark II. Additional protective measures were needed to address the vulnerability of the torpedo armament to enemy fire. The anti-aircraft armament was to be strengthened, and modifications were planned to accommodate more powerful seaplanes.
As part of this modernization, Myōkō underwent its first reconstruction at the Sasebo Navy Yard from November 20, 1934, to March 31, 1935. Key modifications included:
- Removal of the torpedo armament, high-angle guns, and seaplane facilities.
- Installation of eight newly developed 12.7 cm Type 89 high-angle guns in twin mounts, along with upgraded fire-control systems.
- Addition of eight torpedo tubes in rotating quadruple mounts, positioned away from vital areas and fitted with enhanced protection to prevent accidental detonation. A new fire-control system was also installed.
- Installation of new catapults, enabling the simultaneous launch of two seaplanes.
- Construction of improved crew quarters for additional anti-aircraft and aviation personnel, increasing the ship’s complement to between 814 and 832.
- Enhancement of anti-torpedo protection by reinforcing the existing bulges.
After these modifications, all four Myōkō-class cruisers were temporarily assigned to the Fourth Fleet for exercises between July and October 1935, with Myōkō placed in Sentai 3. During these maneuvers, Myōkō sustained damage when a typhoon struck the fleet on September 26.
Following the exercises, a second series of modifications was carried out, including the relocation of fire-control equipment, searchlights, and 7.7 mm machine guns, along with the addition of two quadruple 13 mm Hotchkiss machine gun mounts. After these upgrades were completed in November 1935, Myōkō was reassigned to Sentai 5, part of the Second Fleet.
A third phase of modifications, conducted between January and March 1936, reinforced the ships’ hulls. As the flagship of Sentai 5, Myōkō led the unit in two exercises in April 1936. A fourth round of modifications, completed between May and June 1936, reinforced her mainmast.
From August to September 1936, Myōkō participated in exercises off the coast of Taiwan, again as part of Sentai 5. This final phase of the first modernization process increased her trial displacement to 14,502 tons. However, the added weight reduced her maximum speed and shortened her operational range to 4,000 nautical miles at 16 knots.
By June 1938, plans for a second modernization of the Myōkō-class cruisers were finalized. Myōkō was scheduled for modernization at the Kure Navy Yard in April 1939, but delays occurred as shipyards prioritized earlier refits.
During this overhaul, Myōkō received upgraded fire-control systems and an improved light anti-aircraft armament. The existing 7.7 mm and 13.2 mm machine guns were replaced with four twin-mounted 25 mm Type 96 machine guns amidships and two twin-mounted 13 mm Type 93 machine guns on the bridge. Additionally, two more quadruple torpedo tube mounts were installed.
Other upgrades included replacing the original three ‘SU’ Type searchlights with four more powerful Type 92 searchlights. The catapult and aviation facilities were modernized to support newer aircraft models. The bridge structure was extensively modified and almost entirely rebuilt.
Further modifications to the propulsion system increased Myōkō's displacement and extended her range but slightly reduced her maximum speed. During trials on March 31, 1941, she reached a top speed of 33.88 knots with an output of 132,830 SHP and a displacement of 14,984 tons. Her operational range expanded to approximately 5,000 nautical miles at 18 knots.
The additional armament increased her standard crew complement to 891 men, rising to 970 when serving as a fleet flagship.
Specifications (after second modernization)
| Displacement (full) | 15,933 t |
| Length/Beam/Draft (o/a, m) | 203.8/19.5/6.3 |
| Complement | 970 (as a fleet flagship) |
| Main armament | 20.3 cm (8-in)/50 Type 3 Mark II (2x5) |
| Secondary armament | 12.7 cm (5-in)/40 Type 89 (2x4) |
| Additional armament | 25 mm Type 96 (2x4) |
| 13 mm Type 93 (2x2) | |
| 61 cm Type 92 Model 1 torpedo tubes (4x4) | |
| Aircraft | Two catapults, three reconnaissance aircraft |
| Propulsion | 12 Kanpon boilers (9 boiler rooms) |
| 4 Kanpon geared turbines, 4 shafts | |
| 130,000 SHP (32,500 per set at 320 rpm) | |
| Maximum Speed | 33 knots |
| Range (effective) | 5,000 nm at 18 knots |
Wartime Service
Before their second modernization, Myōkō and her sister ships played an active role in the Second Sino-Japanese War, supporting landings, conducting blockades, and patrolling key areas.
In December 1936, Myōkō was assigned to Sentai 5 in the Second Fleet. On July 28, 1937, she was reassigned as the flagship of Sentai 9 in the Third Fleet. Between August 20 and 23, 1937, she assisted in transporting the 3rd Infantry Division to Shanghai. In February 1938, Sentai 9 was transferred to the Fifth Fleet. Over the next two years, Myōkō completed 23 cruises from her base in Taiwan before being placed in reserve in November 1939 to prepare for her second modernization.
Returning to service on April 10, 1941, Myōkō was reassigned as the flagship of Sentai 5 in the Second Fleet. In preparation for war with the United States, Sentai 5 was transferred to Palau on December 1, 1941, with Myōkō serving as the flagship of Rear Admiral Takagi Takeo. When war broke out, the unit supported Japanese landings in the southern Philippines, moving from Palau to Davao Gulf by the end of December.
On January 4, 1942, while stationed at Davao Gulf, Myōkō was struck by a 600-lb bomb during a surprise raid by eight B-17 bombers. The explosion killed 35 crew members and caused severe damage to the officers' living quarters. She returned to Sasebo on January 9 for repairs, which were completed by February 20.
On February 26, Myōkō arrived in the Makassar Strait in the Dutch East Indies, just in time for the Second Battle of the Java Sea on March 1. During the battle, Myōkō and her sister ship Ashigara engaged the destroyer USS Pope, which ultimately managed to escape. Myōkō returned to the Makassar Strait on March 5.
On March 10, she was reassigned as the flagship of Sentai 5, which was transferred to Sasebo on March 20. During this time, she underwent a brief refit, receiving new gun barrels, improved ventilation, upgraded aircraft, and depth charges.
Sentai 5 was transferred to Truk Atoll on April 27, 1942, departing on May 1 to provide anti-aircraft support for the carriers Shōkaku and Zuikaku. After participating in the Battle of the Coral Sea, the unit returned to Kure on May 22. Initially assigned to the naval force supporting the Japanese attack on Midway in June, Sentai 5 was redirected to assist Japanese landings in the Aleutian Islands following the defeat at Midway on June 7. After supporting the landings at Attu and Kiska, the unit returned to Hashirajima in early July.
On August 17, 1942, the Second Fleet, under Vice Admiral Kondō Nobutake, was transferred to Truk in response to American landings at Guadalcanal. During a sortie north of the Solomon Islands on September 14, the fleet was attacked by ten B-17 bombers, causing minor damage to one of Myōkō's 25 mm gun mounts. The Second Fleet conducted another sortie in October, during which Myōkō bombarded the airfield on Guadalcanal.
Following the Battle of the Santa Cruz Islands on October 26, Myōkō was among the ships that located the burning wreck of the USS Hornet and sank it with torpedoes. The fleet returned to Truk on October 30, and Myōkō arrived in Sasebo on November 10 for refitting. After her refits were completed, she returned to Truk on December 10.
Between January 31 and February 9, 1943, Sentai 5 assisted with the evacuation of Guadalcanal. The unit remained at Truk until early May, when it escorted the battleship Yamato to Yokosuka. In early July, Myōkō underwent refits at Sasebo, after which she was transferred to Kure. These upgrades included the installation of a No. 21 air-search radar and the replacement of her 13 mm machine guns with four additional twin-mounted 25 mm machine guns.
In early August, Sentai 5 assisted in transporting an Imperial Japanese Army detachment to New Guinea before returning to Truk.
On October 9, 1943, Sentai 5 was attached to the Eighth Fleet and transferred to Rabaul, New Guinea, on October 13. During the Battle of Empress Augusta Bay on November 2, Myōkō sustained moderate damage after colliding with the destroyer Hatsukaze. Sentai 5 returned to Sasebo later that month for repairs and modifications, which included the addition of eight single-mounted 25 mm machine guns and a hydrophone for anti-submarine operations. The unit departed from home waters in late December, arriving at Truk on December 29.
On February 10, 1944, Sentai 5 left Truk and arrived at Palau on February 13. In March, the unit was reorganized as part of the First Mobile Fleet and transferred to an archipelago off the coast of Singapore in early April. In May, the fleet moved south of the Philippines to provide cover for multiple reinforcement operations. Between June 19 and 20, Myōkō participated in the Battle of the Philippine Sea.
Returning to Japan for the final time in her career by late June, Myōkō underwent refitting at the Kure Navy Yard. During this overhaul, she received four triple and sixteen single-mounted 25 mm machine guns, significantly bolstering her anti-aircraft defenses. Additionally, she was equipped with No. 13 air-search and No. 22 surface-search radars. To reduce weight, two of her quadruple torpedo tube mounts and a pair of searchlights were removed. These modifications increased her complement to between 1,000 and 1,100 men. She returned to Singapore after the completion of her refits in July.
In late October, Sentai 5 departed for the Philippines, sailing toward the San Bernardino Strait. During the Battle of Leyte Gulf on October 24, Myōkō was struck by a 57 cm Mark 13 torpedo dropped by a TBM-1C torpedo bomber. The hit flooded her starboard propulsion, reducing her speed to 15 knots. She was forced to return to Brunei at the end of October and arrived in Singapore on November 3 for temporary repairs.
On December 12, Myōkō departed for Japan but was intercepted off the coast of Indochina by the submarine USS Bergall. A torpedo struck her aft on the port side, setting her on fire and completely immobilizing her. The crew extinguished the fires by December 15, and she was taken under tow the same day. However, rough seas caused her stern to break off on December 17. She eventually reached Singapore on December 25.
When it became clear that Myōkō could neither be repaired in Singapore nor towed back to Japan, she was repurposed as a stationary anti-aircraft battery against B-29 bomber raids on Singapore. After Japan's surrender, Myōkō formally capitulated to British forces on September 21, 1945. On July 2, 1946, she was scuttled in the Straits of Malacca.
Bibliography
- Lacroix, Eric, and Linton Wells. Japanese Cruisers of the Pacific War. Naval Inst Press, 1997.
- Stille, Mark. Imperial Japanese Navy Heavy Cruisers 1941–45. Bloomsbury Publishing, 2012.
- WW2 Cruisers. “Myoko Class Heavy Cruiser,” 2025. https://www.world-war.co.uk/japan/myoko.php.
