December 1937. Japan's army takes Nanjing, China's capital. For six weeks soldiers off the leash kill prisoners and civilians, rape tens of thousands of women and burn the city. Estimates of the dead run from about 40,000 to 300,000; many historians put it between 100,000 and 200,000.
Why then
Full-scale war began in July, when a skirmish at the Marco Polo Bridge near Beijing escalated. Chiang chose to fight at Shanghai, and three months of street fighting cost Japan far more than it expected. The army that reaches Nanjing is exhausted, brutalised, and taught contempt for the Chinese.
What they wanted
Tokyo expects the fall of the capital to make China submit. Chiang trades space for time and moves the government up the Yangtze. Officers in the field want the campaign over, and treat prisoners as mouths they will not feed.
What changed
A handful of foreigners, among them a German Nazi Party member named John Rabe, run a safety zone that shelters some 200,000 people. China does not submit; the war will last eight years and kill some fifteen to twenty million Chinese. In Japan the massacre is filed for decades under 'incident'.
Still argued
Japanese soldiers' diaries, Western witnesses and the Tokyo war-crimes trial establish that it happened. How many died, and who ordered what, are still fought over in textbooks and between governments.