An important conflict over control of Manchuria and Korea. The Japanese launched a surprise attack on Russian warships at anchor in the naval base at Port Arthur (now Lüshun), Manchuria, without declaring war, after Russia had reneged on its agreement to withdraw its troops from Manchuria. Port Arthur fell to the Japanese, as did Mukden, the capital of Manchuria. The Russian Baltic fleet sailed 28,000 km (18,000 miles) from its base to the East China Sea, only to be destroyed in the Tsushima Straits by the Japanese fleet led by Admiral Togo Heihashiro (1846–1934). This was the first Japanese defeat of a Western power both on land and at sea. The war was ended by the Treaty of Portsmouth. For Russia, it was a humiliating defeat, which contributed to the Russian Revolution of 1905.