In 755 Tang China was arguably the richest, most populous, most cosmopolitan state on earth. Its capital Chang’an held perhaps a million people; its poetry — Li Bai, Du Fu — was in full flower; its census recorded roughly 53 million subjects. The ageing emperor Xuanzong, after four brilliant decades, had withdrawn into life with his consort Yang Guifei, one of the legendary beauties of Chinese history, leaving government to factions — including her cousin, the chancellor Yang Guozhao.
An Lushan was the system’s creation: a general of Sogdian-Turkic origin who, by charming the court (he had himself adopted by Yang Guifei, though nearly twenty years her senior), accumulated command of three frontier military districts — perhaps 150,000-200,000 of the empire’s best troops. His feud with chancellor Yang Guozhao turned lethal, and in December 755 he marched on the heartland, claiming a secret edict to remove the chancellor.
The fall of two capitals
The frontier army cut through the empire’s soft interior, taking the eastern capital Luoyang within weeks, where An Lushan declared his own Yan dynasty. In 756, after a catastrophic Tang decision to force a defensive army out of an impregnable pass at Tongguan, the road to Chang’an lay open.
Xuanzong fled west. At the post station of Mawei, his own escort mutinied, killed chancellor Yang Guozhao, and demanded the death of Yang Guifei herself. The emperor yielded; she was strangled with a silk cord. The scene — the ruler of the world unable to save the woman he loved — became one of the central tragedies of Chinese literature, fixed forever in Bai Juyi’s Song of Everlasting Sorrow. Xuanzong abdicated soon after in favour of his son.
An Lushan did not enjoy it long: increasingly blind and violent, he was murdered in 757 in a plot around his own son, An Qingxu. The rebellion consumed its leaders serially — An Qingxu was killed by the general Shi Siming, Shi Siming by his son — until the last rebel leader died by suicide in 763. The Tang survived only by borrowing cavalry from the Uyghur khaganate, who took the right to sack Luoyang as part of their price.
The bill
The census of 754 recorded about 52.9 million people; that of 764 recorded about 16.9 million. The missing 36 million were not all dead — the wrecked state had simply lost the ability to count refugees and untaxed households — but the true death toll from war, massacre, famine, and disease still ranks among the largest of the pre-modern world, with serious estimates running well into the tens of millions.
The Tang lasted another 144 years but never recovered its reach: the frontier provinces hardened into warlord fiefs, the Silk Road garrisons fell to Tibet, and the dynasty’s golden age was over — ended not by a foreign enemy but by its own best general.