The Treaty of Portsmouth was signed on September 5, 1905 at the Portsmouth Naval Base, Portsmouth, New Hampshire, by Sergius Witte and Roman Rosen (for Russia) and Komura Jutaro and Takahira Kogoro (for Japan), ending the Russo-Japanese War.
The treaty acknowledged Japan as the dominant power in Korea and both sides agreed to evacuate Manchuria and return its sovereignty to China, but Japan was leased the Liaodong Peninsula (containing Port Arthur and Talien) and the Russian rail system in southern Manchuria with access to strategic resources. Japan also received the Island of Sakhalin from Russia. Although Japan gained a lot, that was not nearly as much as the Japanese public had been led to expect. The frustration caused the Hibiya riots and the collapse of Katsura Taro's Cabinet on January 7, 1906.
The negotiations for the treaty were taken under the mediation of Theodore Roosevelt (for which he won the 1906 Nobel Peace Prize), both sides were seeking a peace - the Russians had been repeatedly defeated, but the Japanese were in considerable financial difficulties. Negotiations lasted through August. Prior to the beginning of the negotiations, the Japanese had signed the Taft-Katsura agreement with the US in July, 1905, agreeing to Japanese control in Korea in return for American dominance in the Philippines. Also the Japanese agreed with Britain to extend the Anglo-Japanese treaty to cover all of Eastern Asia and in return for Britain also agreeing to Japan having Korea. The treaty confirmed Japan's emergence as the pre-eminent power in east Asia and forced Russia to abandon its expansionist policies, but it was not well received by the Japanese public.