Seventy years have passed, but historians from the mainland and Japan continue to debate what happened on July 7, 1937.
He Li, chairman of the National Historical Society of the Anti-Japanese War, underlines the unanimous belief among mainland academics that the Marco Polo Bridge Incident was intentional. At the same time, Nihon University's Ikuhiko Hata, a leading Japanese historian, believes it was unplanned.
What both sides do agree upon is that the incident was the trigger for the Sino-Japanese war.
In a speech in Japan this week, Professor Hata traced the start of the fighting to an ill-timed toilet stop by a Japanese soldier. He said reports that the soldier was missing surfaced not long after a dozen shots were fired at Japanese troops at the western end of the bridge on the night of July 6.
The Japanese army telegraphed the Chinese forces the next morning, saying a soldier was missing. They believed he had been kidnapped and taken to the town of Wanping to the east, and demanded entry to search for him.
The request was refused by the Chinese army holding the bridge, and that night Japanese artillery began bombarding the town. The Chinese fought back and the conflict escalated into a war that would last eight years and claim more than 35 million lives.