Emperador Xuanzong de Tang

The longest reign in Tang history, and the hinge of the dynasty. The first three decades — the Kaiyuan era — are the high point of Tang government, poetry and music. The last decade produced An Lushan's rebellion, the flight from Chang'an, and a court that never recovered its authority over the provinces.

He came to power in the coups of 710 and 713, cleared out the factions, and governed for thirty years with a series of unusually capable chief ministers. Li Bai and Du Fu wrote in his reign; he founded the Pear Garden, the imperial music and drama academy, which is why Chinese opera companies still call themselves its disciples.

The frontier commands he created to hold the northwest grew into standing regional armies, and in 755 one of their commanders marched on the capital. Fleeing to Sichuan, his own escort mutinied at the Mawei post station and demanded the death of his consort Yang Guifei. He gave her up, went on to Chengdu, and learned some weeks later that his son had declared himself emperor without asking.

Yang Guifei was never empress. The empress of the reign was Empress Wang, who had helped him seize power in 710 and was deposed in 724 on a charge of sorcery — she had gone to a monk for a charm to help her conceive. She died a few months later, and he appointed no successor to the title.