The Second Sino-Japanese War, which took place from 1937 to 1945, was a major conflict between China and Japan. It began with Japan's invasion of China, marked by significant battles such as the Nanjing Massacre, where Japanese forces committed severe atrocities. This war was characterized by widespread suffering, as millions of Chinese civilians were affected by military actions, contributing to a legacy of enmity between the two nations. This conflict merged with World War II after Japan's attack on Pearl Harbor in 1941, ultimately leading to China's full participation in the broader war against Axis powers.