Mineichi Koga was born in Japan in 1885. He joined the Japanese Navy and served as a naval attaché in Paris before being given command of the Yokosuka Naval Station.

Koga was appointed vice chief of the Naval Staff Board in December 1937 and after the bombing of Pearl Harbor he took part in the capture of Hong Kong.

In April 1943, Admiral Kogo replaced Isoruku Yamamoto as commander in chief of the Combined Fleet. He was unable to halt the decline in the country's fortunes and presided over the start of Japanese withdrawals from the Gilbert Islands and the Philippines.

Mineichi Koga was killed when on 31st March 1944 his aircraft crashed into the sea. His death was not announced until May 1944 when he was replaced as commander in chief by Soemu Toyoda.