Following the Russian rejection of a Japanese plan to divide Manchuria and Korea into spheres of influence, Japan launches a surprise naval attack against Port Arthur, a Russian naval base in China. The Russian fleet was decimated.

The Russo-Japanese War was a war between the Japanese Empire and the Russian Empire. It started in 1904 and ended in 1905. The war happened because the Russian Empire and Japanese Empire disagreed over who should get parts of Manchuria and Korea.

As negotiations broke down, the Japanese opted to go to war, staging a surprise attack on the Russian navy at Port Arthur on February 8, 1904.

The war was caused by competing Russian and Japanese ambitions in the Far East, where the Chinese empire was disintegrating. The Russians had built the Trans-Siberian Railway from Moscow to Vladivostok across Manchuria and had bullied the Chinese into leasing them the ice-free port of Port Arthur as a naval base.

A chromolithograph print by Kasai Torajiro (1904) of the Battle of Port Arthur (8–9 February 1904), marking the beginning of the Russo-Japanese War (1904–05). The attack was planned by Japanese Admiral Togo Heihachiro. Ten torpedo-armed destroyers reached Port Arthur just after midnight on 9 February.

The Soviet Far Eastern reserves – 15 infantry divisions, 3 cavalry divisions, 1,700 tanks, and 1.500 aircraft – were deployed westward in the autumn of 1941 when Moscow learned that Japan would not attack the Soviet Far East, because it had made an irrevocable decision for southward expansion that would lead to war …

Japan staged amphibious attacks on Korea and the Liaodong Peninsula, causing Russian forces to retreat to Mukden. In the Battle of Mukden (early 1905), the Japanese decisively defeated the Russians.

After negotiations broke down in 1904, the Japanese Navy opened hostilities in a surprise attack on 9 February [O.S. 27 January] 1904 by attacking the Russian Eastern Fleet at Port Arthur, China….Russo-Japanese War.