(1894–95), conflict between Japan and China that marked the emergence of Japan as a major world power and demonstrated the weakness of the Chinese empire. The war grew out of conflict between the two countries for supremacy in Korea. Korea had long been China's most important client state, but its strategic location opposite the Japanese islands and its natural resources of coal and iron attracted Japan's interest. In 1875 Japan, which had begun to adopt Western technology, forced Korea to open itself to foreign, especially Japanese, trade and to declare itself independent from China in its foreign relations.

Japan soon became identified with the more radical modernizing forces within the Korean government, while China continued to sponsor the conservative officials gathered around the royal family. In 1884 a group of pro-Japanese reformers attempted to overthrow the Korean government, but Chinese troops under Gen. Yuan Shikai rescued the King, killing several Japanese legation guards in the process. War was avoided between Japan and China by the signing of the Li-Itō Convention, in which both nations agreed to withdraw troops from Korea.

In 1894, however, Japan, flushed with national pride in the wake of its successful modernization program and its growing influence upon young Koreans, was not so ready to compromise. In that year, Kim Ok-kyun, the pro-Japanese Korean leader of the 1884 coup, was lured to Shanghai and assassinated, probably by agents of Yuan Shikai. His body was then put aboard a Chinese warship and sent back to Korea, where it was quartered and displayed as a warning to other rebels. The Japanese government took this as a direct affront, and the Japanese public was outraged. The situation was made more tense later in the year when the Tonghak rebellion broke out in Korea, and the Chinese government, at the request of the Korean king, sent troops to aid in dispersing the rebels. The Japanese considered this a violation of the Li-Itō Convention, and they sent 8,000 troops to Korea. When the Chinese tried to reinforce their own forces, the Japanese sank the British steamer Kowshing, which was carrying the reinforcements, further inflaming the situation.

War was finally declared on Aug. 1, 1894. Although foreign observers had predicted an easy victory for the more massive Chinese forces, the Japanese had done a more successful job of modernizing, and they were better equipped and prepared. Japanese troops scored quick and overwhelming victories on both land and sea. By March 1895 the Japanese had successfully invaded Shandong (Shantung) province and Manchuria and had fortified posts that commanded the sea approaches to Beijing. The Chinese sued for peace.

In the Treaty of Shimonoseki (Shimonoseki, Treaty of), which ended the conflict, China recognized the independence of Korea and ceded Taiwan, the adjoining Pescadores, and the Liaodong Peninsula in Manchuria.

China also agreed to pay a large indemnity and to give Japan trading privileges on Chinese territory. This treaty was later somewhat modified by Russian fears of Japanese expansion, and the combined intercession of Russia, France, and Germany forced Japan to return the Liaodong Peninsula to China.

China's defeat encouraged the Western powers to make further demands of the Chinese government. In China itself, the war triggered a reform movement that attempted to renovate the government; it also resulted in the beginnings of revolutionary activity against the Qing dynasty rulers of China.

(1937–45), conflict that broke out when China began full-scale resistance to the expansion of Japanese influence in its territory (which had begun in 1931). In an effort to unseat the Nationalist (Nationalist Party) government of Chiang Kai-shek, the Japanese occupied large areas of eastern China in 1937–38. A stalemate then ensued, and Japanese forces were diverted to Southeast Asia and to the Pacific theatre of World War II against the Western Powers and their allies beginning in late 1941. Japan's defeat in that by the Allies in 1945 ended its occupation of China.