The Russo-Japanese War was a conflict for control of Korea and parts of Manchuria by the Russian Empire and Empire of Japan that took place from 1904 to 1905. The war is significant as the first modern war where an Asian country defeated a European power. The victory greatly raised Japan's measure in the world of global politics. The war is marked by the Japanese rebuff of Russian interests in Korea, Manchuria, and China, notably, the Liaodong Peninsula, controlled by the city of Port Arthur.

Originally, in the Treaty of Shimonoseki, Port Arthur 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. A year later, the Russian Baltic fleet arrived only to be annihilated in the Battle of Tsushima. While the ground war did not fare as poorly for the Russians, the Japanese army was 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 the 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.

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