July 7

Marco Polo Bridge Incident — Second Sino-Japanese War Begins

Japanese troops conducting night exercises near the Marco Polo Bridge outside Beijing exchanged fire with Chinese soldiers following a confused incident involving a missing soldier. Japan used the incident as a pretext for a full-scale invasion of China.

The Marco Polo Bridge Incident began the Second Sino-Japanese War, which would kill 20 million Chinese and merge into the broader Pacific War in 1941.