Background
The second emperor of the Sui was born to the Yang family, a prominent northern military clan.
The largest share of misery, however, was caused by the emperor's wars of expansion. Under the founding emperor, the Sui had already succeeded in weakening the once mighty Turks, forcing several Turk khlans to acknowledge Sui suzerainty, and the emperor tried repeatedly to conquer the small yet powerful kingdom of Koguryo.
The first Sui expedition in 612 was defeated at Pyongyang. Undeterred, and despite peasant insurgency across the empire, Emperor Yang led a second expedition in 613. Just when the Sui troops were finally about to breach the Koguryo defence, news came that a prominent Sui general had revolted in the rear and was marching on the capital. The expedition was abandoned and though the revolt was quickly suppressed, it signified that members of the ruling aristocracy were started to desert the emperor. In 614, a third expedition was sent against Koguryo but troops began to desert to join insurgent groups. The Koguryo king sued for peace and the expedition was abandoned.
A frequent traveller, the emperor started on the third and last southern tour in 616 as peasant uprising multiplied and the aristocracy became increasingly disaffected.
Emperor Yangis one of the figures traditionally vilified, along with the First Emperor of the Qin and Empress Wu Zetian.