The second son of a doctor in Shizuoka prefecture, Tamon graduated from the 11th class of the Imperial Japanese Army Academy in 1898, and served in the Russo-Japanese War as a junior officer with the IJA 4th Infantry Regiment .

After the end of the war, he graduated from the 21st class of the Army Staff College in 1909.

[2] After spending six months on tour in Europe, Tamon was assigned to the IJA 27th Infantry Regiment based in Vladivostok in 1920 as part of Japan's Siberian Intervention during the Russian Civil War.

In 1931, the division came under the control of the Kwantung Army in Manchuria, and took the lead in the initial operations of the invasion of Manchuria, then in the Jiangqiao Campaign, Jinzhou Operation, and in overcoming the defense of Harbin, following the Mukden Incident.

[4] During interviews with western press following the successful completion of the campaign, he spoke out against criticism by the League of Nations, stating that European gentlemen were unaware of the need to restore peace and order in Manchuria.