Second Sino-Japanese War

The Second Sino-Japanese War began on July 7, 1937 with the Marco Polo Bridge Incident near Beijing — a minor military skirmish that escalated into full-scale invasion as Japan sought to extend its control over China following its 1931 seizure of Manchuria. What followed was eight years of catastrophic warfare that killed between 8 and 22 million people, making it the deadliest conflict in Asian history and one of the most lethal of the 20th century.

Japan's military strategy combined overwhelming conventional force with deliberate terrorization of civilians. The fall of the Chinese capital Nanjing in December 1937 was followed by the Nanjing Massacre — six weeks of organized killing, rape, and looting in which Japanese soldiers murdered an estimated 200,000 to 300,000 Chinese civilians and prisoners of war. The massacre was documented by foreign witnesses in the city, including Nazi Party member John Rabe, and by subsequent war crimes tribunals. It remains a defining atrocity of modern warfare and a major point of historical contention between China and Japan.

Japan's military conducted biological warfare through Unit 731, a covert research unit that experimented on live prisoners and released plague, cholera, and anthrax agents on Chinese cities. Estimates of deaths from biological attacks range from tens of thousands to hundreds of thousands. The Japanese Air Force conducted sustained bombing of Chongqing and other cities, in campaigns that preceded the German bombing of Guernica and London by months or years.

The war created catastrophic humanitarian conditions across occupied China. The Yellow River flood of 1938 — caused by Nationalist Chinese forces deliberately breaking the Huayuankou dike to slow Japanese advance — inundated thousands of square kilometers, destroying harvests and killing an estimated 500,000 to 900,000 people. The 1942–43 Henan famine, exacerbated by wartime disruption, Japanese grain seizures, and Nationalist mismanagement, killed 2–3 million people. Disease spread through refugee populations fleeing the fighting.

After Pearl Harbor in December 1941, the conflict merged with the broader Pacific War. China received Allied assistance through the Burma Road and "The Hump" air route over the Himalayas. The war ended on August 15, 1945, with Japan's surrender following the atomic bombings of Hiroshima and Nagasaki. China emerged devastated but unified — though the civil war between Nationalists and Communists immediately resumed, leading to another 5 million deaths by 1949.