To counter reinforcement of the Russian Empire's Pacific Squadron as tensions rose between the Russians and the Japanese over control of Korea and Manchuria in the early 1900s, Japan ordered the two battleships of the in 1903, the last battleships ordered from abroad. To preempt further reinforcements before their own ships were completed, they began the Russo-Japanese War in 1904 with a surprise attack on the Russian base at Port Arthur. Shortly after the war began, the IJN ordered the two ships of the , the first battleships to be built in Japan. The Imperial Japanese Army captured Port Arthur, along with the surviving ships of the Pacific Squadron by the end of the year. The Russians had dispatched the bulk of their Baltic Fleet to relieve Port Arthur, which reached the Korea Strait in May 1905 and was virtually annihilated by the IJN in the Battle of Tsushima. During the war, Japan captured a total of five Russian pre-dreadnought battleships. They were repaired and commissioned into the Japanese fleet, two of which were later sold back to Russia during World War I, as the two countries were by then allies. The magnitude of the victory at Tsushima caused the leadership of the IJN to believe that a surface engagement between the main fleets was the only decisive battle in modern warfare and would be decided by battleships armed with the largest guns.