Cardboard or Lying
In 1935, the Royal Navy’s Director of Naval Construction was briefed on Japan’s new Mogami-class cruisers. Japan claimed they displaced 8,500 tons. They carried fifteen 155mm guns in five triple turrets.
His response: “They must be building their ships out of cardboard or lying.”
They were lying. The actual design weight was 9,500 tons. At trials, Mogami displaced 11,169 tons. And those 155mm gun turrets? The barbettes were designed from the start to be swapped for 203mm heavy cruiser guns whenever Japan felt like dropping the pretense.
Japan was a signatory to the London Naval Treaty, which limited cruiser displacement and armament. The Mogami class was a treaty violation on a blueprint.
Mogami herself was built at the Kure Navy Yard and completed in July 1935. Three sisters followed: Mikuma, Suzuya and Kumano, all finished by 1937.
The Hull That Cracked
The first warning arrived before Mogami was even launched. In March 1934 the torpedo boat Tomozuru, a 600-ton boat carrying three 12.7cm guns and the torpedo outfit of a destroyer, capsized in rough weather off Sasebo. She was top-heavy. The Navy ordered a stability review of every ship built, building or planned, and the Mogami design was on that list.
But the cheating came with consequences. The designers had packed too much onto the hull. Mogami was dangerously top-heavy, a problem the US Navy would later wrestle with in its own Cleveland-class cruisers. On September 26, 1935, Mogami and Mikuma were caught by a typhoon during fleet exercises. Both came out with deformed hulls. Welding technology was still new, and the welds failed under stress. The fire control directors and turrets became unusable from vibration. On Mikuma, firing the full main battery at once was enough to pop welds along her sides.
The Navy retrofitted hull bulges to Mogami and her sister Mikuma, increasing beam to 20.5 meters and displacement to 11,200 tons. They cut the bridge down by two-thirds. Removed the seaplane hangar. Rebuilt the aft superstructure fifty percent lighter. It cost them two knots of speed.
In 1939, Japan dropped the treaty pretense entirely and swapped all the 155mm guns for ten 203mm guns. The turrets they removed went to the Yamato-class battleships.
Torpedoes in the Wrong Direction
The rebuilt cruisers got their first real fight on the night of February 28, 1942, in the Sunda Strait. USS Houston and HMAS Perth ran into the Japanese invasion force landing troops on western Java. Mogami and Mikuma joined the action.
Mogami fired a spread of six Type 93 torpedoes at Houston. The sources do not even agree on that number: the Combinedfleet movement record says six, while the NavWeaps order of battle credits Mogami with twelve torpedoes launched during the battle. Either way, the spread aimed at Houston missed. They kept running into the crowded anchorage behind the target, where Japanese transports were unloading.
One of the ships hit was the transport Shinshu Maru, also listed as Ryujo Maru. Aboard was Lieutenant General Hitoshi Imamura, commander of the 16th Army and the man in charge of the whole invasion of Java. He had to abandon ship and was picked up by a small boat and taken ashore. Houston and Perth were both sunk that night. The Japanese records were quiet about who had put the general in the water.
Midway: The Wrong Turn
Then came Midway. June 5, 1942. Admiral Yamamoto ordered Cruiser Division 7 to shell Midway Island at 35 knots. USS Tambor, an American submarine, was spotted. The flagship and Suzuya executed the emergency turn correctly. Mikuma made a 90-degree turn instead of the ordered 45. Mogami, right behind her, turned 45 degrees as commanded.
Mogami rammed Mikuma’s port side below the bridge. Her bow caved in. Mikuma’s fuel tank ruptured, leaving a trail of oil.
The usual telling blames Mikuma’s helmsman. But Mogami was following closely enough that a correct 45-degree turn still put her bow into her sister’s side. Four heavy cruisers in tight column at 35 knots, at night, turning on a submarine alarm, left no margin for a single mistake. Whoever ordered that formation and speed owns part of the collision too.
American dive bombers followed the oil slick. On June 6, Mikuma took at least five direct hits from Dauntless dive bombers. At 1:58 PM her own Type 93 torpedoes began to explode, wrecking the catapult deck and the mainmast and blowing out part of the hull below the waterline. She rolled onto her port side and sank that evening.
The Combinedfleet record puts her dead at 700, with about 240 survivors picked up by Mogami and a destroyer. The US submarine Trout later fished two more out of the water. Mogami took six bomb hits, lost turret No. 5, and had 91 crew killed and 101 wounded, according to the Combinedfleet record. Naval Encyclopedia puts her dead at 81. Either way, she survived.
The Navy rebuilt her. From September 1942 to April 1943, Sasebo Naval Arsenal removed her two aft turrets and extended the flight deck to carry eleven reconnaissance seaplanes. She came out the other end as a hybrid aviation cruiser: six 203mm guns forward, a flight deck aft.
The new arrangement did not keep her out of trouble. On November 5, 1943, Rear Admiral Frederick C. Sherman sent 97 aircraft from the carriers Saratoga and Princeton against the Japanese cruisers that had just arrived at Rabaul. Mogami was hit by a 500-lb bomb at anchor and set on fire. She was one of several cruisers damaged that morning, alongside Maya, Takao and Atago, and she left under her own power. One of the carriers in that raid, Princeton, was a converted Cleveland-class cruiser hull.
Surigao Strait
In this configuration, she fought at the Battle of Surigao Strait on October 25, 1944, part of the Battle of Leyte Gulf. American battleships, many of them Pearl Harbor survivors, crossed the T on the Japanese force in the last battleship-versus-battleship engagement in history.
Four 203mm shells from USS Portland destroyed Mogami’s bridge and her air defense station, killing both the captain and executive officer. Then the Japanese flagship Nachi collided with the crippled Mogami while trying to retreat.
American carrier planes hit her again the next morning. At 12:40 PM, the destroyer Akebono put a single Long Lance torpedo into her. Mogami finally sank by the bow at 1:07 PM, with 192 dead: 191 crew and one civilian employed by the navy. The Combinedfleet record puts her grave at 09-30N, 124-56E, in the Mindanao Sea.
Her sisters did no better. Mikuma was gone at Midway. Kumano outlived Mogami by exactly one month, until November 25, 1944, when aircraft from USS Ticonderoga caught her at Santa Cruz on the west coast of Luzon and hit her with five torpedoes and four 500-lb bombs.
Three names. Two collisions. Two rebuilds. One ship.
Sources
- Mogami-class cruiser (Wikipedia)
- IJN Mogami: Tabular Record of Movement (Combinedfleet.com)
- IJN Mikuma: Tabular Record of Movement (Combinedfleet.com)
- IJN Kumano: Tabular Record of Movement (Combinedfleet.com)
- Mogami class cruisers (Naval Encyclopedia)
- Capsize of torpedo boat Tomozuru (Failure Knowledge Database)
- The Secret of the Battle of Sunda Strait (Naval Historical Society of Australia)
- Orders of Battle: Battle of the Sunda Strait (NavWeaps)
- World War II Raids on Rabaul, November 1943 (HistoryNet)
- Lacroix, Eric, and Linton Wells II. Japanese Cruisers of the Pacific War. Naval Institute Press, 1997.
