From 1930 to 1933, as lieutenant general, Tamon commanded IJA 2nd Division. 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, Chinchow Operation, and in overcoming the defense of Harbin, following the Mukden Incident. 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.