Portsmouth, Treaty of, 1905, treaty ending the Russo-Japanese War. It was signed at the Portsmouth Naval Base, New Hampshire, on Sept. 5, 1905. Negotiations leading up to the treaty began in the spring of 1905 when Russia had suffered severe defeats and Japan was in financial difficulties. Therefore, both nations indicated a desire for peace. Germany, the United States, and Great Britain were instrumental in forcing conciliation between the belligerents. However, the United States and Britain exacted certain concessions from Japan before smoothing the way for the treaty. President Theodore Roosevelt demanded that Japan follow the Open Door policy in Manchuria and return the region to Chinese administration. In the Taft-Katsura agreement of July, 1905, Roosevelt agreed to Japanese dominance in Korea in return for American freedom of action in the Philippines. Great Britain had the Anglo-Japanese treaty extended to cover all of E Asia and in return also gave Japan a free hand in Korea. Under the terms of the Portsmouth agreement, Russia was compelled to recognize Korea's independence and the "paramount political, military, and economic interests" of Japan in Korea. Russia also agreed to place Manchuria again under the sovereignty of China, and all foreign troops were to be removed. The railway lines in S Manchuria, constructed by Russia, were ceded to Japan without payment. The disputed Liaodong peninsula (see Liaoning), containing the ports of Dalian and Port Arthur (see Lüshun, was turned over to Japan, as was the southern part of the island of Sakhalin. Japan also obtained fishing rights in the waters adjacent to the Russian Far East. The Treaty of Portsmouth marked the temporary decline of Russian power in East Asia and the emergence of Japan as the strongest power in the area.
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