In the Seinan War, Iwao fought against Takamori SAIGO, his relative, as a commander of the government army, and never returned to Kagoshima because this was his concern throughout his life.
西南戦争では政府軍の指揮官として親戚筋の西郷隆盛を相手に戦ったが、大山はこのことを生涯気にして、二度と鹿児島に帰る事はなかった。