It is not clear how it is defined until now. It's been estimated for eight years. From the September 18th Incident of 193 1 to the July 7th Incident of 1937, it was not an all-people war of resistance, but only some people in the northeast were at war. After the July 7th Incident, it was a real national war of resistance and a part of the world anti-fascist war. Moreover, before the July 7th Incident, the National Government did not declare war on Japan, nor did it defend itself. Only after the July 7th Incident did it declare self-defense, which was the real beginning of the war between the two countries. Declare war on Japan after Pearl Harbor.