The Japanese Mogami Class Cruisers

Imperial Navy Cruisers of the Rising Sun in World War II

Jul 15, 2009

The Mogami class heavy cruisers of the Imperial Japanese Navy were a supporting actor in the great naval Battles in the Pacific in World War Two

A noble effort at world peace after the WWI led to a series of Naval Arms limitations that culminated in the London Naval Treaty. These limitations placed the cap of 10,000 tons on cruisers.

Original Design of the Mogami

The Imperial Japanese Navy drew up plans for a 4-vessel class of “light” cruisers that would weigh in at some 8600-tons. The weight savings were realized by such methods that included carrying smaller caliber guns, using an innovative aluminum superstructure, having a welded hull when most contemporary warships were riveted and other ideas. Armor, however, was not neglected and the ships carried 5 full inches (125mm) of plating over magazines and a 3.9 inch (100mm) belt across other high value parts of the ship’s hull. They could withstand non-superstructure hits from anything but a heavy cruiser or battleship. These ships were 661 feet in length and engined with a quartet of steam turbines that would propel them at some 37 knots. The cruisers carried 15 high elevation 6 inch (155mm) guns as a main armament but were designed to be able to be retrofitted with larger 8-inch (203mm) weapons with a minimum of effort. Secondary weapons included a number of smaller 127mm and 40mm antiaircraft guns and ten deadly Type 93 Long Lance torpedo tubes. Each cruiser carried 3-4 float-equipped seaplanes, first the Nakajima E8N "Dave" and Mitsubishi F1M "Pete" biplanes and later the sleek and more heavily armed Aichi E13A "Jake" monoplane.

Subsequent Improvement to Heavy Cruisers

These ships were classified as the Mogami class after the lead ship and took to the waves in between 1935 and 1937. In 1938, with tensions over the war in China pointing towards ominous naval conflict with the United States, the Mogami's were "up-armored" significantly. They were placed in shipyards where they quickly had their main batteries of 155mm guns replaced with 10 of the much more deadly 203mm weapons while keeping all of its secondary batteries and torpedoes. They were fitted with large below-water torpedo blisters along the hull to defeat the warheads of enemy submerged weapons. The changes to the quartet of Mogami cruisers nearly doubled their originally designed weight to some 13670 tons full load. This reclassified them as heavy cruisers and made them a match for the United States Navy’s slightly smaller USS New Orleans (CA-32) and Royal Navy’s County classes of purpose- built heavy cruisers.

Brief History of the Class in Service

The four ships of the Mogami class were the Mogami, Mikuma, Suzuya and Kumano. Two half-sisters of a greatly modified design were the Chikuma and Tone. Mikuma survived The Battle of Sunda Strait where she helped send the Australian cruiser Perth and the USS Houston to the bottom only to be caught with her pants down at the Battle of Midway. Mikuma had been badly damaged in a collision with her sister the Mogami while only 90 miles off of Midway island. The two cruisers were caught by wave after wave of US carrier and land based planes two days after the pivotal battle and churned to junk metal. Mikuma slipped below the surface forever just before her most famous picture was taken. Mogami limped back to Japan and was converted to a cruiser-carrier only to be lost in an epic last stand in the Battle of the Surigao Strait. The Chikuma was lost in the Battle off Samar on 25 October 1944 after her famous surface action with the tin cans USS Samuel B. Roberts and USS Heermann. Suzuya was likewise dispatched in the same battle by the air wings of three US “Jeep Carriers". Finally the Tone and Kumano who had seen quiet service across the Pacific, were sunk by carrier aircraft in the last year of the war while in harbor.

Not a single one of these Japanese cruisers had survived the war, much less lived past their tenth birthday in commission.

Actions and Activities after 4 June 1942 -- Sinking of Japanese Cruiser Mikuma, 6 June 1942 Department of the Navy, Naval Historical and Heritage Command.

Howarth, Stephen. The Fighting Ships of the Rising Sun: The Drama of the Imperial Japanese Navy, 1895-1945. Athenaeum

Jentsura, Hansgeorg. Warships of the Imperial Japanese Navy, 1869-1945. Naval Institute Press

The copyright of the article The Japanese Mogami Class Cruisers in WW II History is owned by Christopher Eger. Permission to republish The Japanese Mogami Class Cruisers in print or online must be granted by the author in writing.