The were a class of four heavy cruisers built for the Imperial Japanese Navy (IJN) in the mid-1930's. All four fought in World War II, and were sunk.

Design

For the 1931 Fleet Replenishment Program, believing themselves understrength in cruisers, the IJN chose to build to the maximum allowed by the Washington Naval Treaty. This resulted in the choice of 155 mm guns in five triple turrets (a first for Japan) in the Mogamis, also capable of 55° elevation, making Mogamis one of the very few classes of Cruiser to have a Dual Purpose (DP) main battery; this was coupled with very heavy anti-aircraft protection, as well as the standard reloadable, turreted torpedo tubes, also unique to the IJN.

To save weight, electric welding was used, as was aluminium in the superstructure. Aiming to meet the weight limits compelled them to fit only ten boilers (compared to twelve in the previous Takao and Myoko classes), trunked into a single funnel stack (which also saved tophamper). The new impulse geared turbines added 22,000 shp over Atago, increasing the top speed by 1.5 knots (2.8 km/h). Protection, however, was not stinted on; the class proved able to take substantial punishment.

The designers, however, had overreached; excessive topweight led to instability, and gunnery trials revealed cracking hull welds. Hull bulges were retrofitted to Mogami and Mikuma, and added to Kumano and Suzuya, increasing beam to 19.2 m (63 ft) and displacement to 11,200 tons, cutting speed by 2 kt (3.7 km/h).

Beginning in 1939, the class was brought in for substantial reconstruction, replacing the triple 155 mm turrets with twin 203 mm (8-inch) guns, turning over the 155 mm turrets for the battleship Yamato. Indeed, the designers had designed the class in mind so that the 6-inch guns could be switched with 8-inch batteries, in effect making them heavy cruisers and skirting the London Naval Treaty. Torpedo bulges were also added; in all, displacement rose to over 13000 tons, and speed dropped to 34.5 kt (63.8 km/h).

War Service

In June 1942, all four took part in the Battle of Midway, where Mogami and Mikuma collided trying to avoid a submarine attack; Mikuma was finished off on 6 June 1942 by aircraft from and . The heavily damaged Mogami limped home and spent ten months in yard, during which her afterparts were completely rebuilt, and "X" and "Y" turrets were replaced by a flight deck (with the intention to operate 11 aircraft).

In October 1944, the survivors were reunited at the Battle of Leyte Gulf. Mogami, heavily damaged by a collision with Nachi, cruiser gunfire and aerial attack was scuttled by Akebono, while Kumano stumbled into Manila harbor on one boiler, to be put out of her misery by Halsey's aviators on 25 November 1944; they mauled Suzuya the same day, and she was scuttled by Okinami on 27 November.

Criticism

This class is seen by naval architects as trying to fit a quart into a pint pot. The IJN's Naval staff insisted that each new class be superior to anything else in its category, this placed an enormous burden on Japanese naval constructors and the difficulties with these ships have to be seen in this light.

The initial construction was extremely light in order to comply with the naval treaties and had to be remedied. When the Royal Navy's Director of Naval Construction (DNC) was told about these ships by British Naval Intelligence quoting the public displacement figure he replied that the capabilities quoted could not be achieved on this displacement and that "they must be building their ships out of cardboard or lying".

Though the placement of Turret #3 improved its firing arc, and though the class had the stability problems fixed (the preceding Takao-class cruisers were considered too top-heavy), the Mogami's are generally not considered an improvement over the Takao's Nonetheless, the follow-up Tone-class retained many aspects of the Mogami-class design. However, the Tone's were intended for a different purpose with all of their main armament forward, so their stern could accommodate extra floatplanes.

Ships

Name	Builder	Laid	Launched	Completed
Mogami	Kure Navy Yard	October 1931	March 1934	July 1935
Mikuma	Mitsubishi, Nagasaki	December 1931	May 1934	August 1935
Suzuya	Yokosuka Navy Yard	December 1933	November 1934	October 1937
Kumano	Kawasaki, Kobe	April 1934	October 1936	October 1937

References

NotesBibliography

• Blair, Clay (1975). Silent Victory. London: Lippincott.
• D'Albas, Andrieu (1965). Death of a Navy: Japanese Naval Action in World War II. Devin-Adair Pub. ISBN 0-8159-5302-X.
• Dull, Paul S. (1978). A Battle History of the Imperial Japanese Navy, 1941-1945. Naval Institute Press. ISBN 0-87021-097-1.
• Fitzsimons, Bernard (1978). The Encyclopedia of 20th Century Weapons and Warfare, Volume 18. London: Phoebus.
• Lacroix, Eric; Linton Wells (1997). Japanese Cruisers of the Pacific War. Naval Institute Press. ISBN 0-87021-311-3.
• Preston, Anthony (2004). World's Worst Warships. London: Conway's Maritime Press.

External links

• Hackett, Bob; Sander Kingsepp Mogami class. Imperial Japanese Navy Page (Combinedfleet.com). (2006). Retrieved on 2006-06-14..