After the Crimean War, Russia had turned her attention once more to the East. There had been hostilities with China over eastern Siberia, which were brought to an end in 1858 by the Treaty of Aigun, under which China ceded certain territories in northern Manchuria. This made possible the founding of Vladivostok in 1860. Russia received Sakhalin from Japan in 1875 in exchange for the Kurile Islands. She received from China the important Port Arthur as a leased territory, and then tried to secure the whole of South Manchuria. This brought Japan's policy of expansion into conflict with Russia's plans in the Far East. Russia wanted Manchuria in order to be able to pursue a policy in the Pacific; but Japan herself planned to march into Manchuria from Korea, of which she already had possession. This imperialist rivalry made war inevitable: Russia lost the war; under the Treaty of Portsmouth in 1905 Russia gave Japan the main railway through Manchuria, with adjoining territory. Thus Manchuria became Japan's sphere of influence and was lost to the Manchus without their being consulted in any way. The Japanese penetration of Manchuria then proceeded stage by stage, not without occasional setbacks, until she had occupied the whole of Manchuria from 1932 to 1945. After the end of the second world war, Manchuria was returned to China, with certain reservations in favour of the Soviet Union, which were later revoked.