On this day in 1904, the first great war of the twentieth century began, the Russo-Japanese War. Lasting until September 1905, it began out of tensions over the rival imperial ambitions of the Russian Empire and the Empire of Japan over Manchuria and Korea.
From the end of the First Sino-Japanese War and 1903, negotiations between Russia and Japan had proved impractical. Japan offered to recognise Russian dominance in Manchuria in exchange for recognition of Korea as a Japanese sphere of influence. Russia refused this, so Japan declared war to counter the Russian aggression in Asia. The Japanese defeated the Russians in a series of battles on land and at sea.
The war saw more than 150,000 troops killed on both sides of the conflict.