From the end of the Meiji period to the beginning of the Taisho period, he increasingly became influential since he, as the chief of the General Staff, had led Japan to victory in the Russo-Japanese War (note, however, that Emperor Meiji trusted Katsura more than Yamagata, and he sometimes asked Katsura for advice in disregard of Yamagata) and because Hirofumi ITO had been assassinated.
日露戦争では参謀総長として日本を勝利に導いたこと（ただし明治天皇は、山縣より桂を信頼しており、山縣の頭越しに桂へ諮詢することもあった）、伊藤博文が暗殺されたことにより、明治末期から大正初期にかけては山縣の発言力は増大した。