A native of Yokohama in Kanagawa Prefecture, where his father was a naval engineer, Komatsubara graduated from the 18th class of the Imperial Japanese Army Academy in 1905.

[1] On Komatsubara's return to Japan in 1915, he graduated from the 27th class of the Army Staff College and was assigned as commander of the IJA 34th Infantry Regiment.

From 1919, Komatsubara was assigned to the Soviet Branch of the 4th Section (European & American Military Intelligence), 2nd Bureau, of the Army General Staff.

Promoted to lieutenant general in 1936, he was reassigned to Manchukuo as commander of the IJA 23rd Division, and served on the staff of the Kwantung Army.

While in retirement he joined the National Policy Research Association attending meetings, and sharing his knowledge and experience of both the Russians and the Battle of Khalkhin Gol (Nomonhan).