how did the Sui dynasty come to power?

At the end of the Northern and Southern Dynasties (386 - 589), the whole nation had undergone a long period of division. People who had endured sufferings of war were longing for the unification but neither the Northern Dynasties nor Southern Dynasties realized this goal. In Northern Zhou (557 - 581), Yang Jian, who was born to the noble class and was the Chengxiang (Prime Minister) of the last emperor, monopolized the political and military power and suppressed the separatist forces as well as some other royal forces. In 581, Yang Jian replaced Northern Zhou with Sui and proclaimed himself Emperor Wen. Thus Sui was founded.