Born in Suo Province, Kodama fought in the Boshin Civil War 1868, the Saga Rebellion 1873, and the Satsuma Rebellion 1877. After studying in Germany, as head of the Army Staff College, he worked for the adoption of the German military system. He served in the Sino-Japanese War of 1894-1895 and, afterward, as Governor-General of Taiwan. Kodama was army minister in the fourth Ito Hirobumi cabinet (1900) and in the succeeding Katsura Taro cabinet, in which he was also minister of both home affairs and education. Promoted to full general in 1904, during the Russo-Japanese War of 1904-05 he served as chief of general staff of the Manchurian Army and assisted in the capture of Port Arthur. In 1906 he was named chief of the Army General Staff.