Which decisive naval battle in 1905 gave Japan control of the seas?

The decisive naval battle that gave Japan control of the seas in 1905 was the Battle of Tsushima. Fought on 27–28 May in the Tsushima Strait, it pitted Japan’s Combined Fleet under Admiral Tōgō Heihachirō against Russia’s Baltic Fleet during the Russo-Japanese War.

The Russian fleet had sailed roughly 18,000 nautical miles from the Baltic Sea to reach the Far East, arriving exhausted and poorly positioned. Japan’s forces used scouting, wireless telegraphy, superior manoeuvrability, and concentrated gunfire to break the Russian formation. The result was a devastating Japanese victory: nearly the entire Russian fleet was sunk, captured, or forced to surrender.

Tsushima was more than a naval defeat. Russia lost the ability to challenge Japan’s control of the waters around Korea and Manchuria, while the scale of the victory made Japan the first modern Asian power to defeat a major European empire in a war. Russia soon agreed to peace negotiations, leading to the Treaty of Portsmouth in September 1905.

The Battle of Port Arthur and the Battle of the Yellow Sea were important earlier engagements, but neither produced the same decisive destruction of Russia’s main fleet.