Japanese Navy

Strength and organization of the Imperial Japanese Navy in December 1941 at the Pearl Harbor raid. Ships of the Combined Fleet and Japanese Naval Air Force.

Superbattleship 'Yamato'
Superbattleship ‘Yamato’

The Prime Minister presided over Imperial General Headquarters (GHQ) which was split in two sections – Army and Navy. Holding positions at Imperial GHQ were the Navy Minister and the Chief of the Navy General Staff, Admiral Osami Nagano. Other officers and departments handled the responsibilities of staff and ministry.

The Imperial Japanese Navy at the beginning of WW2

Executing the naval instructions emanating from Imperial GHQ was the C-in-C of all seagoing warships. This was Admiral Isoroku Yamamoto, and following his death in April 1943, his successors were Admiral Mineichi Koga, Admiral Soemu Toyoda (from March 1944) and Admiral Jisaburo Ozawa (from May 1945 to the end of the war).

In addition to the responsibility for implementing strategic moves generally, they were also expected to take tactical command of the most important operation in progress. Admiral Yamamoto flew his flag in the battleship Nagato until the super-battleship Yamato was commissioned on 16 December 1941. There was a constant restriction on radio communication whenever she put to sea, and at such crucial times, the C-in-C was out of touch with all but the immediate situation.

From May to September 1944, the C-in-C’s flagship was the Oyodo, a command cruiser for combined striking forces of submarines and aircraft. Although permanently anchored first in Tokyo and then in Hiroshima Bay, her communications facilities proved inadequate. The HQ of C-in-C Combined Fleet was finally located at Keio University in the Tokyo suburb of Hiyodashi.

As its name implies, the Combined Fleet (Rengo Kantai) was just that – the whole Navy. All other units, regardless of function or size, were designated as tai or butai, both of which could be translated as corps, force or body. The intelligence sections of other navies assigned the terms fleet, squadron and division for the purpose of description as appropriate.
It was customary for groups of smaller warships to be led by a bigger one. Thus, four destroyers made up a division, four divisions a destroyer squadron, plus a cruiser as flagship. A somewhat similar organization existed for submarines.
For administrative purposes, the Combined Fleet was divided into lesser fleets according to function.

Japanese battlecruiser Kirishima
The Kirishima, one of the four Kongo class battlecruisers build during World War I. They were all rebuild from 1933 to 1940 as fast battleships with eight 36.6 cm guns and a top speed of 30 kn.

Japanese Navy December 1941

Ships of the Combined Fleet:

FiguresShip classesunder construction
Battleships10 4 Kongo, 2 Fuso, 2 Ise, 2 Nagato 3 (Yamato, one later as aircraft carrier Shinano)"
Aircraft Carriers8 1 Hosho, 1 Akagi, 1 Kaga, 1 Ryujo, 2 Hiryu, 2 Shokaku (1941)8
Heavy Cruisers18 2 Furutaka, 2 Aoba, 4 Myoko, 4 Takao, 4 Mogami, 2 Tone1
Light Cruisers20 2 Tenryu, 1 Yubari, 5 Kuma, 3 Jintsu, 6 Natori 9 (just 8 finish at the end of WW2)
Destroyers108 3 Momi, 13 Minekaze, 7 Wakatake, 4 Kamikaze, 12 Mutsuki, 20 Fubuki, 4 Akatsuki, 6 Hatsuhara, 10 Shiratsuyu, 10 Asashio, 18 Kagero (1939-41), 1 Yugumo (1941)43

Japanese Naval Air Force

Apart from 370 training and reserve machines, the Japanese Naval Air Force totaled approx. 1,400 aircraft. There were 660 fighters (mainly A6M Zeros), 330 carrier-borne strike aircraft, 240 twin-engined shore-based torpedo-bombers specifically intended for fleet cooperation, and 520 flying boats and seaplanes.

All these aircraft were organized in the Combined Air Fleet, based at Kanoya, and were subdivided into the 1st Air Fleet (the Carrier Fleet) and the 11th Air Fleet (under Vice-Admiral Nishizo Tsukuhura) shore-based in Formosa and Indochina. The fleets were further divided into air flotillas (each commanded by a rear-admiral), which were themselves composed of two or more air groups. Each air group comprised a base unit and 12 to 36 aircraft with 4 to 12 in reserve, depending on size. The combat formation was the air division of about nine airplanes.

Mitsubishi A5M Claude
Two Mitsubishi A5M Claude over China. These fighters turned the tables on the Chinese and achieved complete air supremacy.

References and literature

World War II – A Statistical Survey (John Ellis)
The Armed Forces of World War II (Andrew Mollo)
Fighting Ships of the World (Antony Preston)
Flotten des 2. Weltkrieges (Antony Preston)
Kriegsschiffe von 1900 bis heute – Technik und Einsatz (Buch und Zeit Verlagsgesellschaft)
Das große Buch der Luftkämpfe (Ian Parsons)

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4 thoughts on “Japanese Navy”

  1. Battleships (ex battle cruisers) Kongo class were armed with 8 14-inch guns, i.e. 35,56 cm … The list is missing the battleships Kongo class (Kongo, Hiei, Haruna, Kirishima), Fuso class (Fuso, Yamashiro), Ise class (Ise, Hyuga) and Nagato class (Nagato, Mutsu).
    Breyer, Siegfried (1973). Battleships and battle cruisers, 1905–1970. Garden City, New York: Doubleday.
    Conway’s All the World’s Fighting Ships, 1922-1946
    Jane’s Fighting Ships 1922
    Preston, Antony (1972). Battleships of World War I: An Illustrated Encyclopedia of the Battleships of All Nations 1914–1918. New York: Galahad Books
    Rohwer, Jurgen (2005). Chronology of the War at Sea, 1939–1945: The Naval History of World War Two. Annapolis, Maryland: Naval Institute Press.
    Skulski, Janusz (1998). The Battleship Fusō: Anatomy of a Ship. London: Conway Maritime Press
    Whitley, M. J. (1998). Battleships of World War Two: An International Encyclopedia. Annapolis, Maryland: Naval Institute Press

  2. The title “Japanese Navy 1939-40” does not fit well here. To this, Soryu and Hiryu were treated as separate classes, both of which differed greatly. Under construction were two aircraft carriers (Shokaku class), rebuilding Takasaki for the Zuiho aircraft carrier ended on December 27, 1940. At the same time, started works on the completion of Junyo and Hiyo aircraft carriers, rebuilt from passenger ships Kashiwara Maru and Izumo Maru. November 15, 1940, the decision was made to rebuild Tsurugizaki on Shoho, but the work began in January 1941. Taigei was rebuilt to aircraft carrier from December 1941 to November 1942. In 1940 under construction were 5 aircraft carriers, less than stated in the table. The creator of the table forgot to add two heavy cruisers, Tone and Chikuma, completed between 1938 and 1939 and forgot mention the conversion of light cruisers Mogami class (4 ships) to heavy cruisers. Ibuki cruiser’s keel was laid on April 24, 1942. And there were 19 Fubuki destroyers, Miyuki sank on June 29, 1934 and did not survive until 1939.

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