This is because the government needed a person of noble birth with authority as their symbol to oppose the charismatic leader SAIGO and also had to avoid causing a power struggle between the Army and the Navy by appointing Lieutenant General and Vice Admiral to the seconds-in-command instead of appointing one of them to the supreme commander.
これは、カリスマ的指導者である西郷に対抗して権威のある貴種を旗印として用いるためと、どちらか一方を総司令官にせずに、同じ中将の2人を副官に据えることで、陸軍と海軍の勢力争いを回避するためであった。