From 1904 to 1905 the war was fought by Russia and Japan over their interests in China (particularly Manchuria) and Korea—areas of strategic importance to each country. Before fighting broke out Japan moved to settle the conflict, but the overture was rejected by Tsar Nicholas II (1868–1918), and Japan soon severed all diplomatic relations (on February 6, 1904) with Russia. Two days later the Japanese issued a surprise attack on Russian ships at Lushun (Port Arthur), Manchuria. On February 10 Japan officially declared itself at war with Russia. The battles—both on land and at sea—went badly for the Russian forces, which could not be adequately reinforced or supplied to meet the powerful and disciplined Japanese. Early in 1905, the war effort already unpopular back home, revolution broke out in Russia, further weakening the country’s resolve.

After an eight-month siege at Lushun, it became clear that Russia could no longer muster a fight. Further, the war was expensive for Japan, which sought the intervention of the United States in settling the conflict. President Theodore Roosevelt (1858–1919) became involved in mediating the dispute; a peace treaty was signed September 5, 1905, at a shipyard in Portsmouth, New Hampshire, following one month of deliberations. The terms of the treaty were these: both nations agreed to evacuate Manchuria; Russia ceded to Japan the southern half of Sakhalin Island, which lies between the two countries (the island was ceded back to Russia after World War II); Korea became a Japanese protectorate; and Russia transferred to Japan the lease of China’s Liaodong Peninsula. And so Japan emerged as a power onto the world scene.