In late 755 the frontier general An Lushan revolted against the Tang court, took the eastern capital Luoyang and in 756 entered Chang'an, then the largest planned city on earth, forcing the emperor to flee to Sichuan. Eight years of civil war followed, with both capitals sacked more than once, Uighur allies permitted to plunder Luoyang, and a massacre of foreign merchants at Yangzhou in 760. Registered population in the census fell catastrophically after the war, reflecting both deaths and the collapse of state registration and land allocation. The Tang survived but never restored central control over its provinces, revenue or its equal-field land system.
The rebellion broke the Tang model of the capital as a walled grid of gated, curfewed wards under direct state administration, and shifted economic weight to the Yangtze delta and the canal cities. The commercial city that followed, with shops fronting open streets, night markets and no ward walls, became the Song urbanism of Kaifeng and Hangzhou and the enduring template for East Asian market towns.
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