The Russo-Japanese War was fought between the Empire of Japan and the Russian Empire during 1904 and 1905 over rival imperial ambitions in Manchuria and Korea. The major theatres of military operations were the Liaodong Peninsula and Mukden in Southern Manchuria, and the seas around Korea, Japan, and the Yellow Sea.
Russia sought a warm-water port on the Pacific Ocean both for its navy and for maritime trade. Vladivostok remained ice-free and operational only during the summer; Port Arthur, a naval base in Liaodong Province leased to Russia by the Qing dynasty of China from 1897, was operational year round. Since the end of the First Sino-Japanese War in 1895, Japan feared Russian encroachment on its plans to create a sphere of influence in Korea and Manchuria. Russia had demonstrated an expansionist policy east of the Urals in Siberia and the Far East from the reign of Ivan the Terrible in the 16th century.
Seeing Russia as a rival, Japan offered to recognize Russian dominance in Manchuria in exchange for recognition of Korea being within the Japanese sphere of influence.