The Battle of Tsushima in the Sea of Japan was between what two countries?

The Battle of Tsushima in 1905 was a decisive victory for Imperial Japanese Navy against the Second Pacific Navy of the Russian Empire. Russia's defeat ensured a Japanese victory in the on-going Russo-Japanese War (1904-1905).

The war stemmed from the two countries rivalry at the expense of a declining China. Both countries sought expansion into Korea and Manchuria. Russia's push for a warm water Pacific port conflicted with Japan's push for a greater sphere of influence in the area.

Tensions led to a Japanese sneak attack on the Russian Far East Fleet at Port Arthur in 1904. The Siege of Port Arthur and several other defeats necessitated the transfer a majority of the Russian Baltic Fleet to the Pacific in an attempt to buy time until reinforcements would tilt the balance in Russia's favor.

The undertaking of such a feat was dangerous and costly. Further, after the fall of Port Arthur, the only safe haven was Vladivostok. Approaching Vladivostok, the rechristened Second Pacific Fleet was attacked by the Japanese on May 27-28, 1905. Despite having 8 Battleships to the Japanese 5, the Russians were no match for the Japanese, who had a total 89 ships to the Russian 38. Moreover, superior Japanese equipment and tactics helped to decimate the Russian fleet. Only three Russian ships reached Vladivostok. The rest were sunk, scuttled, or captured. The Japanese lost three torpedo boats.