Eventually, he formed the 'The Yamagata Bureaucratic Faction' across the Army, Ministry of Inner Affairs, Imperial Household Ministry and Privy Council in order to facilitate his involvement in politics by becoming a supporter of Taro KATSURA and Masatake TERAUCHI in the Army as well as of government bureaucrats such as Keigo KIYOURA and Tosuke HIRATA.
以後は、陸軍・内務省・宮内省・枢密院などにまたがる「山県系官僚閥」を形成して、陸軍では桂太郎や寺内正毅、官僚では清浦奎吾や平田東助らの後ろ盾となって政治に関与するようになる。