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Second Sino-Japanese War

Japan invaded China proper in 1937, beginning a war against both Chiang Kai-shek 's Nationalists and also the Communists of Mao Zedong 's united front. On December 13 of that same year, the Nationalist capital of Nanjing surrendered to Japanese troops. In the event known as the " Nanjing Massacre ", Japanese troops killed many tens-of-thousands of people associated with the defending garrison. It is estimated that as many as 200,000 to 300,000 including civilians, may have been killed, although the actual numbers are uncertain and possibly inflated—coupled with the fact that the government of the People's Republic of China has never undertaken a full accounting of the massacre. In total, an estimated 20 million Chinese, mostly civilians, were killed during World War II. A puppet state was also set up in China quickly afterwards, headed by Wang Jingwei. The Second Sino-Japanese War continued into World War II with the Communists and Nationalists in a temporary and uneasy nominal alliance against the Japanese.