The war was a conflict between the Russian Empire and the Empire of Japan over rival imperial ambitions in Manchuria and Korea.

Japan, angered by Russia's presence in Manchuria and the earlier Triple Intervention, launched a surprise attack on the Russian fleet at Port Arthur.

The war was fought on a massive scale with modern military technology, including machine guns and rapid-firing artillery.

Japanese forces won a series of major land battles, including the long and bloody Siege of Port Arthur.

The decisive engagement of the war was the naval Battle of Tsushima.

At Tsushima, the Japanese fleet, under Admiral Togo, annihilated the Russian Baltic Fleet, which had sailed for months to reach the battle.

The war was the first major military conflict of the 20th century.

U.S. President Theodore Roosevelt mediated the peace negotiations, earning him a Nobel Peace Prize.

The war ended with the Treaty of Portsmouth, a major victory for Japan.

It was the first time in the modern era that an Asian power had defeated a major European power, and it had a profound global impact.