Terauchi Masatake
From 30 April 1916 to 29 September 1918, Ōshima was Minister of War under Prime Ministers Ōkuma Shigenobu and Terauchi Masatake. He entered the reserves in 1919 and served as a member of the House of Peers in the Diet of Japan from 1920. From 1940-1946, he was a member of the Privy Council.