July 7, 1937, marks the beginning of the Second Sino-Japanese War, a significant conflict between China and Japan that lasted until 1945. This date is crucial as it represents the Marco Polo Bridge Incident, where clashes erupted between Chinese and Japanese troops, escalating tensions that had been brewing due to Japan's aggressive expansion in China. This incident not only sparked full-scale war but also highlighted the growing militarism of Japan and China's struggle for sovereignty amidst foreign aggression.