Tsukamoto commanded the IJA 21st Infantry Brigade during the Boxer Rebellion and early in the Russo-Japanese War, including the Battle of Nanshan. In September 1904, he was promoted to lieutenant general. He succeeded General Ogawa Mataji as commander of the IJA 4th Infantry Division after the latter was wounded in combat during the Battle of Liaoyang. He continued to command the division through the Battle of Mukden. After the end of the war, he was reassigned to command the IJA 9th Infantry Division.