Obviously, there were existing problems between China and Japan. But the immediate cause for the fighting that started on that date was a missing Japanese soldier. I’ve read about the incident in several different sources. The consensus was that the guy didn’t show up for roll call; that he was reported missing; and that the officers in charge of his unit demanded permission to search a nearby Chinese town and were denied which led to the fight which in turn led to a general war. I’ve also read that the soldier was actually only missing for a few hours and was already back when the shooting started. And I’ve heard “urban legends” that he had been drinking in a bar or visiting a brothel.
But one thing I can’t find is his name. No source I’ve seen names this missing soldier.
I can see where it must be a little embarassing to show up a couple of hours late one day and cause World War II as a result but you’d think his name would not be lost to history.
It was SOP for Japan at the time to manufacture or blow up small incidents as an excuse to attack. This was just another one.
It did, however and IMHO, mark the difference in China’s stance to Japan switching from concilatory to resistance…and therefore (IMHO) is the true start date of WWII.