What happened
An Lushan rose at Fanyang in December 755 and took Luoyang, then Chang’an. Emperor Xuanzong fled toward Sichuan; at Mawei his soldiers forced the death of his consort Yang Guifei. Continued by An’s successors and Shi Siming — hence the name 安史 — the rebellion was suppressed by 763 with Uyghur help.
Background
An Lushan was a military governor (jiedushi) of Sogdian-Turkic descent who commanded large armies on the northeastern frontier.
Consequences
Loss of life was enormous, and the administrative collapse shows in the census records. Tang central power never fully recovered: provinces under military governors became semi-autonomous, and the fiscal system shifted with the two-tax reform of 780.