Sino-Japanese Wars or Chinese-Japanese Wars, struggles in the 19th and 20th centuries between China and Japan over predominance in East Asia.

For centuries Korea was a tributary state of China. During the 19th century, however, Japan emerged as a military power in East Asia and threatened China’s close relationship with Korea. Anxious to exert its military influence, Japan secured the Treaty of Kanghwa with Korea in 1876, ostensibly to protect Japanese fishermen in the Korea Strait. A provision of the treaty declared Korea unilaterally independent, which weakened China’s association with Korea. Fearing a Japanese takeover of the peninsula, China encouraged Korea to also sign treaties with the United States, Britain, France, and Germany to increase international recognition of Korea’s independence. China, however, continued to expect a privileged relationship with Korea.

In March 1894 there was a domestic revolt against the Korean monarchy by the Tonghak religious cult, an antiforeign secret society. Both China and Japan sent troops to help put down the rebellion. Once it was over, China proposed immediate withdrawal of foreign troops. On the pretext of helping to effect political and military reforms, however, Japan declared that its forces would remain in Korea. The Japanese occupied the royal palace, and in July they made a surprise attack on Chinese naval vessels stationed in Korean waters. A short conflict on land and sea followed and Japan won a decisive victory.

By the terms of the Treaty of Shimonoseki, concluded on April 17, 1895, China was forced to acknowledge the complete independence of Korea; to cede the island of Taiwan, the P’enghu Islands, and the Liaodong Peninsula in northeastern China to Japan; and to pay a large indemnity. Concerned that the treaty would destabilize the colonial balance of power in East Asia, Russia, France, and Germany then forced a revision of the Treaty of Shimonoseki under which Japan had to renounce its claim to Liaodong.

During the 1920s militarists gained control in Japan’s government. Their aim was to use force to extend Japanese influence into China, which had been weakened by revolution. Japan also wanted to expand its territories both to relieve its problem of overpopulation and to obtain badly needed natural resources.

In September 1931 Japan alleged that the Chinese had sabotaged part of the Japanese-controlled South Manchurian Railway. The Japanese invaded Manchuria and gained control of the city of Mukden (now Shenyang) with its large Chinese garrison. They set up a puppet government and renamed the region Manchukuo. In response to Chinese resistance, in 1932 the Japanese attacked Shanghai and pillaged the countryside. The League of Nations branded Japan an aggressor in October and Japan withdrew from the league several months later. During the next few years Japanese forces in Manchuria exerted military pressure in northern China and by 1935 had moved into parts of Chahar (now part of Inner Mongolia Autonomous Region) and Hebei provinces.

In July 1937 a serious clash between Chinese and Japanese troops at the Marco Polo Bridge near Beijing precipitated a full-scale, though undeclared, war between the two countries. The threat posed by Japan temporarily united the Kuomintang (KMT) and the Chinese Communist Party (CCP) in an uneasy political truce. The Chinese were hampered by their lack of industrial bases and well-trained army officers and enlisted men. The Japanese quickly captured the major cities in northern China, including the KMT capital of Nanjing. In 1938 the Japanese also seized Hankou (now part of Wuhan) in central China and Guangzhou in the south. KMT leader Chiang Kai-shek led his armies westward into the interior and established the new wartime capital at Chongqing, in Sichuan province. The Japanese were able to cripple the Chinese economy and isolate Chiang’s forces by capturing the entire coastal strip of China and cutting off communications with the interior. The Chinese, however, continued to resist the Japanese.

In Asia the Second Sino-Japanese War was a prelude to World War II, just as the Spanish Civil War had been to the war in Europe. In 1940 Italy, Germany, and Japan established an alliance known as the Rome-Berlin-Tokyo Axis. On December 7, 1941, Japan attacked Pearl Harbor, Hawaii. The next day China declared war on Japan and the other Axis powers. As a result, desperately needed supplies and troops began to pour into China from both the United States and Great Britain. At the same time the dispersion of many Japanese troops to other battlegrounds in the Pacific theater relieved the pressure on China. Fighting against the Japanese continued in China until Japan surrendered to the Allies in August 1945 after atomic bombs were dropped on Hiroshima and Nagasaki.