July 7, 1937Reputable sourceWell documented
The Second Sino-Japanese War Begins
On the timeline · around July 7, 1937 ·
What happened
A clash between Japanese and Chinese troops at the Marco Polo Bridge (Lugou Bridge) near Beijing escalated within weeks into a full-scale Japanese invasion of China. Following the Battle of Shanghai, Japanese forces captured the Nationalist capital of Nanjing later that year.
Why it matters
The fighting that began at the Marco Polo Bridge is widely treated as the opening of World War II in Asia and the Pacific — years before war broke out in Europe.