In 617 Li Yüan (566–635), the Duke of T'ang and one of the most powerful Sui generals, joined the scores of rebels who had arisen in the waning years of the Sui dynasty. His armies marched on the Sui capital, overwhelmed its defences, and took the city. There, six months later, he founded a new dynasty which was to endure for almost three centuries, and would rank alongside the Han as one of China's two golden ages of empire. As Li Yüan went on to impose firm central authority throughout the country, he was fortunate in being the heir to the great achievements of the Sui, who, barely three decades before, had brought centuries of disunion to an end. The institutions of his new dynasty were established on the solid foundations left by his predecessors.

Like the majority of rebel leaders throughout Chinese history who succeeded in founding dynasties of their own, Li Yüan was not a commoner but a nobleman of distinguished lineage. His ancestry can be traced with certainty as far as his grandfather, Li Hu, one of the ‘Eight Pillars of State’ (Pa Kuo-chu), the chief commanders associated with Yü-wen T'ai in the foundation of the Northern Chou state in the 550s. At that time the Li clan was centred on Wu-ch'uan chen, a garrison established by the Toba state of Northern Wei inside the Great Wall near modern Tat'ung, which was also the home of Yü-wen T'ai.