Oka Ichinosuke

Oka was born in Hagi in Chōshū domain (present day Yamaguchi Prefecture. He graduated from the 4th class of the Imperial Japanese Army Academy in 1881, and from the 4th class of the Army Staff College in 1888.

Oka served as Vice Commander of the IJA 8th Infantry Brigade, and subsequently as commander of the IJA 20th Infantry Regiment. During the First Sino-Japanese War, he was Chief of Staff of the IJA 1st Division.

After the war, Oka served in various administrative and staff positions within the Imperial Japanese Army General Staff. At the time of the Russo-Japanese War, he was working in the Military Affairs Department. Oka was promoted to major general in 1905. He subsequently commanded the IJA 27th Infantry Brigade and the IJA 29th Infantry Brigade before being promoted to lieutenant general in February 1912, and commander of the IJA 3rd Division in 1913.

In April 1914, Oka became Minister of War under Prime Minister Ōkuma Shigenobu.

He resigned in March 1916 due to ill health, and was ennobled with the title of baron (danshaku) under the kazoku peerage system just before his death in July of the same year.