On July 7th, 1937, conflict broke out between the Republic of china and the japanese empire. This military conflict formed into the beginning of the second sino-japanese war. (1937-1945) On august 18th 1937, japanese imperial forces invaded the chinese city of shanghai. On december 9th, Japanese demanded that the chinese army protecting nanjing surrender, the chinese did not. so on December 12th, 1937; Chinese guards of Nanjing were forced to retreat after the Japanese started invading. On December 13th, at approximately 3:00am, Japanese forces seized the gate to the city of Nanjing. They opened the gate and the Japanese invaded. In the first three days, there were over 15,000 deaths. On December 17th, They held mass executions. Executions continued daily until January of 1938, when the massacre was condemned.