The Tang Dynasty ruled China from 618 to 907 AD and expanded China's territory. Two important early emperors were Gao Zu and Tai Zong. Empress Wu later seized power as the only female emperor and reintroduced the imperial examination system to select scholar officials. However, she was overthrown in a coup at age 80. The Battle of Talas in 751 diminished Tang power against the Arabs. Culturally, the Tang embraced Central Asian, Indian and Persian influences and shared innovations like paper, printing, and tea with the West. The Tang economy transitioned to a direct tax system and used paper money. Peasant revolts eventually contributed to the dynasty's end.