The Lugou Bridge Incident, also known as the Marco Polo Bridge Incident, was a clash between Chinese Nationalist forces and Japanese troops that occurred on July 7, 1937, marking the beginning of the Second Sino-Japanese War. This event was significant as it highlighted the escalating tensions between China and Japan during a period when the Nationalist government sought to unify the country and confront foreign aggression. The incident symbolized the collapse of diplomatic efforts and set the stage for widespread conflict in East Asia.