The Second Sino-Japanese War was the war fought between the Republic of China and the Empire of Japan from 1937 to 1945 as part of World War II. It is often regarded as the beginning of World War II in Asia. It was the largest Asian war in the 20th century and has been described as "the Asian Holocaust", in reference to the scale of Japanese war crimes against Chinese civilians. It is known in Japan as the Second China–Japan War, and in China as the Chinese War of Resistance against Japanese Aggression.
On 18 September 1931, the Japanese staged a false flag event known as the Mukden Incident, a pretext they fabricated to justify their invasion of Manchuria. This is sometimes marked as the beginning of the war. From 1931 to 1937, China and Japan engaged in skirmishes in mainland China. Japan achieved major victories, capturing Beijing and Shanghai by 1937. Despite having fought each other in the Chinese Civil War since 1927, the Communists and Nationalists formed the Second United Front in late 1936 to resist the Japanese invasion together.
Tensions escalated after what would become the first battle of the war - the...