In 1936 Ozawao was promoted to rear admiral and the following year was appointed chief of staff of the Combined Fleet. In 1940 he became a vice admiral and president of the Japanese Naval Academy.
Ozawao was placed in command of the Japanese Mobile Fleet. When the US Marines began landing on 15th June 1944, Ozawao was sent to rescue the situation but his fleet was badly destroyed by the US Navy. He later used his crippled fleet as a decoy at Leyte Gulf and was successful at drawing Admiral William Halsey away from the San Bernardino Strait.