Political map of Russia & the former Soviet Union 07 February 1904 (Outbreak of the Russo-Japanese War): Russia's tightening influence in Manchuria (Manchuria) and Korea led to tensions with Japan. With the Russians also building the Trans-Siberian Railway (Trans-Siberian Railway) to connect their European heartland to the Far East, the Japanese decided they had to act quickly to prevent total Russian domination of the region. On February 8, the Japanese launched a surprise torpedo attack on the Russian Pacific Fleet at Port Arthur (Battle of Port Arthur), triggering war (Russo-Japanese War).