The Sino-Japanese War, also known as the Second Sino-Japanese War or the China Incident, began on July 7, 1937 and lasted until September 2, 1945. It was a military conflict between China and Japan that was part of the wider Second World War (1939-1945).
The war emerged from a long-running dispute over control of Manchuria and Korea, which had been formerly under Chinese rule. In 1931, Japan invaded Manchuria and created a puppet state, Manchukuo, in 1932. In response, the League of Nations strongly condemned the act, but most Western countries, including the United States, acquiesced to it.
In 1933, Chinese Nationalist forces attempted to block Japan’s advance by occupying the demilitarized zone of Jehol, near the Chinese-Manchurian border. This led to a full-scale invasion of northeast China by Japanese forces on July 7, 1937, the start of the Sino-Japanese War. After months of fierce fighting, the Japanese captured Beijing and Tianjin in 1938 and Nanjing (the then capital of China) in December of that year.
Initial Chinese resistance was limited, as the Nationalist government, led by Chiang Kai-shek, had concentrated most of its forces to fight the Communist-led Chinese Red Army. However, the Chinese political leadership changed in April 1938; Chiang Kai-shek was replaced by Lin Biao as the leader of the Nationalist Party. This shift in power allowed the Chinese to organize a larger-scale counteroffensive and created the famous Stilwell Road Campaign which is often cited as a major contributor to the eventual Chinese victory.
Furthermore, the entry of the United States into World War II shifted the balance heavily in favor of China. US forces provided financial, military, and moral support that ultimately helped China repel the Japanese invasion. US President Franklin D. Roosevelt authorized two aid packages to China which included weapons, equipment and supplies. In addition, the US Navy initiated numerous air and naval campaigns against Japanese shipping routes and ports in the region, cutting off vital supply lines and eventually leading to Japan’s surrender in 1945.
In spite of US and Chinese efforts, the Sino-Japanese War caused immense destruction and death in both China and Japan, with estimates ranging from over 20 million deaths in China, to between 1 and 2 million in Japan. It was one of the bloodiest events in history, and set the stage for further Japanese expansion in East Asia. Furthermore, the war also marked a shift in power in Asia, as the victorious Chinese Nationalists established the Republic of China (ROC) on mainland China, while the Japanese-backed State of Manchuria was disestablished. The ROC eventually defeated the Communists in 1949, and would remain in power until the establishment of the People’s Republic of China in 1949.