The Tang capital, Chang'an (present-day Xi'an), is…

The Tang capital, Chang'an (present-day Xi'an), is the most populous city in the world at this time.

The first century of the Tang dynasty has so far been one of the most prosperous and brilliant periods in the history of Chinese civilization.

The empire now extends so far across Central Asia that for a while Bukhara and Samarkand are under Chinese control, the Central Asian kingdoms pay China tribute, and Chinese cultural influence reaches Korea and Japan.

Chang'an has become the greatest city in the world; its streets are filled with foreigners, and foreign religions—including Zoroastrianism, Buddhism, Manichaeism, Nestorianism, Christianity, Judaism, and Islam—flourish.

This confident cosmopolitanism is reflected in all the arts of this period.

Li Longji, born in 685 into an era when power was virtually in the hands of his grandmother, the Empress Wu Zetian, widow of Emperor Zhongzong, had become the only glimmer of hope for the restoration of the imperial Li family.

His aunt, the Princess Taiping, daughter of the Empress, had fiercely protected Longji from harm by the Wu family.

In conspiring with Princess Taiping to put an end to the Empress’s attempted usurpation of power, Longji had killed Empress Wei in 710 a palace coup which had placed his own father, Emperor Ruizong, on the throne.

Longji had been appointed chancellor for a few months before becoming the crown prince.

Tensions between Princess 'aiping and Li Longji had soon mounted, however.

Princess Taiping, who has many supporters at court, hopes to ascend the imperial throne as her mother Empress Wu had done.

Ruizong exiles his sister to the provinces, hoping to defuse tension, but Longji, who fears that Princess Taiping would hold him responsible for her exile and would have him murdered, asks his father to recall the princess, who is allowed to return to the imperial court.

Eventually, in September 712, a disgruntled Ruizong, tired of court feuds, abdicates in favor of his son, who becomes Emperor Tang Xuanzong.

Suddenly it is Princess Taiping who is at risk of falling victim.

Alarmed by Ruizong's decision, the princess manages to have the court name him Taishang Huang (sometimes translated as "retired emperor", or "emperor emeritus"), a position in which Ruizong is to keep effective control of power with the new emperor Xuangzong only formally attending court audiences and ceremonies.

Appointments to high offices, controlled by Ruizong, are filled with the Princess' supporters.