Tatsumi was promoted to major general in June 1894 and was assigned command of the IJA 10th Infantry Brigade. During the First Sino-Japanese War he was distinguished by his role in the 1894 Battle of Pyongyang. After the end of the war, He was ennobled with the rank of "danshaku" (baron) under the "kazoku" peerage system in August 1895.After the war, he was briefly commandant of the Army Staff College, and was then head of the Japanese military bureau within the Government-General of Taiwan from April 1896.