Japan's campaign of aggression against China began with the seizure of Manchuria in 1931. The Manchurian takeover elicited Chinese reprisals against Japanese nationals in Shanghai, including the murder by a mob of a Japanese Buddhist monk, which in turn prompted an armed Japanese intervention in that city. A vicious but localized Sino-Japanese war raged around the Shanghai region through much of 1932. The conflict then settled into a quiescent phase for several years. Japan proceeded to consolidate its hold on Manchuria, while China was distracted by simmering civil war between Chiang Kai-shek's Nationalists and Mao Zedong's Communists. Preoccupied with the Great Depression and the rising menace of Hitler, the Western world bore distant and largely helpless witness to the sputtering crisis in Asia.

A minor clash between Chinese and Japanese troops at the Marco Polo Bridge, near Beijing, touched off full-scale war between the two Asian powers in July of 1937. Japan and China were both by then spoiling for the fight. Open war offered an opportunity once and for all to chastise what Tokyo regarded as the exasperatingly feckless Chinese regime. In Japanese eyes, a British diplomat reported,

China is not a civilized state, but a chaotic amorphous mass whose government is powerless to maintain order. Communism is rampant there, and the country is prey to the depredation of the armies of rival war lords, red communist armies and roving bodies of bandits.

For his part, Chiang, under pressure from his generals and the Communists, ravened for the chance to come to grips with the Japanese aggressor in a decisive showdown. Soon foiled, however, in his attempt to engage the main body of Japanese troops near Beijing, Chiang sought to shift the arena of combat to the south by replaying the scenario of 1932. His minions menaced the 30,000 Japanese residents of Shanghai, hoping to draw Japanese forces out of the north and into the great valley of the Yangtze, Chiang's main political base and supposedly most secure military stronghold.

The lure worked. Tokyo turned its eyes southward, and the Japanese commander Matsui Iwane began the investment of Shanghai on August 23. He made tortuous headway against fierce but patchy Chinese resistance. (Chiang's generals executed several hundred of their soldiers for cowardice.) After suffering 30 percent casualties, Matsui's forces at last took Shanghai in early November, a military disaster for Chiang and the prelude to greater disasters that soon followed. Behind a rolling carpet of ferocious bombing, the Japanese began moving up the valley of the Yangtze toward Chiang's capital at Nanjing.

The bloody Yangtze. Less than a century earlier its teeming watershed had been convulsed by some of the worst fighting of the Taiping rebellion, a horrific fourteen-year upheaval that claimed 20 million Chinese lives. In the decade before the Japanese incursion Chiang's unruly armies had ruthlessly exterminated Communists and labor unionists along the lower Yangtze. They also looted the British, American, and Japanese consulates and murdered several foreigners. Through this historic cauldron of seething hatreds and prolific violence Matsui's troops now advanced. Chiang's soldiers scattered before them in a pell-mell rout that swelled to maniacal panic as the fighting neared the gates of Nanjing. Nationalist government officials fled the city as the Japanese drew close. Chiang himself abandoned his capital on December 8. He left behind a ragtag force under General Tang Sheng-chih to mount what rear-guard defense it could. Tang quickly gave up even the pretense of resistance. After ordering the houses outside the city walls to be set aflame as a delaying action, he boarded a launch that churned away up the Yangtze on the evening of December 12. Deserted by their leaders and fearful of being trapped inside the city by a ring of fire, the remnants of the Nanjing garrison and the additional troops streaming into the city from the lower Yangtze stampeded for what safety they could find. Thousands swarmed into the frigid waters of the river, in what quickly proved a suicidal quest for the refuge of the far shore. More thousands sought to disguise themselves and hide within the beleaguered city. They stripped off their military uniforms, looted shops and assaulted civilians for nonmilitary clothing, trampled and axed and machine-gunned their comrades, in a mad scramble to elude the oncoming invaders.