gaki was born to a samurai family in Seto-town, Bizen Province (currently Okayama Prefecture). He graduated from the Imperial Japanese Army Academy in 1891, and the Army Staff College in 1900.
Ugaki was sent as military attaché to Germany from 1902–1904 and again from 1906-1907. In 1910, he was promoted to colonel and in 1915 was promoted to major general, at which time he was made Commandant of the Army Staff College from 1919–1921 and commander of the IJA 10th Division from 1921-1922. In 1923, Ugaki became Vice Minister of the Army