Early life and career

Koga was born in the ceramics center of Arita in Nishimatsuura County of Saga Prefecture in 1885. He entered the 34th class of the Imperial Japanese Naval Academy and graduated in 1906, ranked 14th of 176 cadets.

He served as midshipman on the cruiser Matsushima on its long-distance navigational training cruise to Honolulu, Hilo, Wellington, Brisbane, Palm Island, Queensland, Batavia, Singapore, Mako, Qingdao, Port Arthur, Dairen, Chemulpo, Chinkai, Busan and Kagoshima. On his return, he was commissioned as ensign and assigned to the Katori, followed by Otowa and Suma.

As a sub-lieutenant he served on the Soya and Aki, and as lieutenant from 1911, he served on Kashima.

After further attendance at Japan's Naval War College, Koga held shore staff posting following his graduation and promotion to lieutenant commander in 1917. In 1920, having seen no action during World War I, Koga became a resident officer in France. He returned in 1922 to become executive officer on the Kitakami. On his promotion to captain on December 1, 1926, Koga was again posted to France, where he served as a naval attaché in Paris until November 1, 1928.

Recalled to Japan in 1930 and being given command of the Yokosuka Naval Station, Koga captained the heavy cruiser Aoba from December 31, 1930, and the battleship Ise from December 31, 1931, until his appointment to rear admiral on December 31, 1932 and transfer to be Chief of the Imperial Japanese Navy General Staff's Intelligence Division in 1933.

Koga became Vice Chief of the Navy General Staff and was promoted to vice admiral on December 31, 1936 shortly before the beginning of the Second Sino-Japanese War in 1937.

Commander of the IJN 2nd Fleet in 1939, Koga was placed in command of the China Area Fleet on September 1, 1941. Koga shared Yamamoto's misgivings about war with the United States, but disagreed with Yamamoto regarding the use of naval aviation, remaining a firm battleship advocate until events later in the Pacific War proved his position outdated.

Pacific War

Commander in Chief of the Combined Fleet

Tsuneo Matsudaira, Shigetarō Shimada, Mineichi Koga, and Saburō Hyakutake on the deck of the battleship Musashi, June 1943

Following the death of Admiral Isoroku Yamamoto on April 18, 1943, Koga succeeded Yamamoto as Commander in Chief of the Combined Fleet. His flagship was the battleship Musashi. Koga attempted to revitalize Japanese naval operations by reorganization of the Combined Fleet into task forces built around aircraft carriers in imitation of the United States Navy, and organized a land-based naval air fleet to work in coordination with the carriers. Operationally, he intended to mount an aggressive counteroffensive, first in the Aleutians to dilute American forces and eventually to lure the American fleet into a major naval engagement in late 1943.^[2] However, the losses of Japan's land and carrier based aircraft in the Southwest Pacific eventually forced a Japanese withdrawal from the Solomons to the aero-naval base complex at Rabaul in the Bismarcks by the end of the year, and the simultaneous defeat in the Gilbert Islands of the Central Pacific in November 1943. Koga gradually adopted a more conservative stance, attempting to conserve his remaining forces for a decisive battle to inflict maximum damage on the Americans when they closed toward the 'Inner Defense Lines' of the Marianas and Philippines (code named "Z plan"). An additional strategic change in late 1943 was the establishment of the Grand Escort Command of better organized convoys and increased ASW vessels in the face of increasingly successful U.S. submarine attacks on Empire shipping lanes, although this would not be nearly enough to prevent the collapse of the Japanese merchant marine over the following year.

Books

• D'Albas, Andrieu (1965). Death of a Navy: Japanese Naval Action in World War II. Devin-Adair Pub. ISBN 0-8159-5302-X.
• Dupuy, Trevor N. (1992). Encyclopedia of Military Biography. I B Tauris & Co Ltd. ISBN 1-85043-569-3.
• Fuller, Richard (1992). Shokan: Hirohito's Samurai. London: Arms and Armour Press. ISBN 1-85409-151-4.
• Morison, Samuel Eliot (2002). History of United States Naval Operations in World War II. Vol. VI: Breaking the Bismarcks Barrier, 22 July 1942 – 1 May 1944. Chicago: University of Illinois Press.
• Morison, Samuel Eliot (2002). History of United States Naval Operations in World War II. Vol. VII: Aleutians, Gilberts, and Marshalls, June 1942 – April 1944. Chicago: University of Illinois Press.
• Morison, Samuel Eliot (2002). History of United States Naval Operations in World War II. Vol. VIII: New Guinea and the Marianas, March 1944 – August 1944. Chicago: University of Illinois Press.