Japan and China fought the first Sino-Japanese War during 1894 and 1895, primarily over control of Korea. To distinguish from the second Sino-Japanese War, this war is called "Jiawu War" (甲午戰爭) in Chinese because it occurred in the Chinese year by that name.
Korea (under the Joseon Dynasty) had traditionally been a tributary state to China. In 1875 the Qing Dynasty of China had allowed Japan to recognise Korea as an independent state. However China continued to try to assert influence over Korea, and public opinion in Korea split, with conservatives wanting to retain a close relationship with China while reformists wanted Korea to modernize and to have a closer relationship with Japan.
Following the assassination of a pro-Japanese reformist in 1894, a Korean religious sect, the Tonghak, began the Tonghak Peasant Revolution. The Korean government requested from China help in suppressing it.
However, when China did contribute assistance, the Japanese government sent an expedition in support of the reformists, and had seized the royal palace in Seoul by June 8, 1894. War between Japan and China was officially declared on August 1, 1894, though some naval fighting had already taken place.
The Japanese navy mauled China's northern fleet off the mouth of the Yalu River at the Battle of Yalu on September 17, 1894. The Chinese fleet lost 8 out of 12 warships, retreated behind the fortifications of the Weihaiwei naval base, and was then caught by a surprise Japanese land attack across the Liaodong Peninsula, which shattered the ships in harbour with shelling from the landward side. After Weihaiwei's fall on February 2 and an easing in harsh winter conditions, Japanese troops pressed their advance into Manchuria.
Faced with these repeated defeats China signed the Treaty of Shimonoseki in April 1895.
The defeat of China at the hands of Japan highlighted the failure of the Chinese army to modernize adequately, and resulted in increased calls within China for accelerated modernization and reform.
See also: Sino-Japanese War (1937-1945)