Originally, in the Treaty of Shimonoseki, Ryojun had been given to Japan. This part of the treaty was overruled by Western powers, which gave the port to the Russian Empire, furthering Russian interests in the region. These interests came into conflict with Japanese interests. The war began with a surprise attack on the Russian Eastern fleet stationed at Port Arthur, which was followed by the Battle of Port Arthur. Those elements that attempted escape were defeated by the Japanese navy under Admiral Togo Heihachiro at the Battle of the Yellow Sea. Following a late start, the Russian Baltic fleet was denied passage through the British-controlled Suez Canal. The fleet arrived on the scene a year later, only to be annihilated in the Battle of Tsushima. While the ground war did not fare as poorly for the Russians, the Japanese forces were significantly more aggressive than their Russian counterparts and gained a political advantage that culminated with the Treaty of Portsmouth, negotiated in the United States by the American president Theodore Roosevelt. As a result, Russia lost the part of Sakhalin Island south of 50 degrees North latitude (which became Karafuto Prefecture), as well as many mineral rights in Manchuria. In addition, Russia's defeat cleared the way for Japan to annex Korea outright in 1910.