ポーツマス条約
He also served as a Japanese judge in the Permanent Court of Arbitration at The Hague along with Ichiro Motono. Denison subsequently assisted Komura Jutaro in negotiating the Anglo-Japanese Alliance. During the Russo-Japanese War (1904–1905), he travelled with Kaneko Kentarō to the United States, and assisted in the drafting of the Treaty of Portsmouth.