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.
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 that same fall.
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.
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. 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 that same fall. 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.
Mineichi Koga