War fought between China and Japan. After Korea was opened to Japanese trade in 1876, it rapidly became an arena for rivalry between the expanding Japanese state and neighbouring China, of which Korea had been a vassal state since the 17th century. A rebellion in 1894 provided a pretext for both sides to send troops to Korea, but the Chinese were rapidly overwhelmed by superior Japanese troops, organization, and equipment. After the Beiyang fleet, one of the most important projects of the Self-Strengthening Movement, was defeated at the battle of the Yellow Sea and Port Arthur (now Lüshun) captured, the Chinese found their capital Beijing menaced by advancing Japanese forces. They were forced to sign the Treaty of Shimonoseki, granting Korean independence and making a series of commercial and territorial concessions which opened the way for a Japanese confrontation with Russia, the other expansionist power in north-east Asia.