577 The Northern Zhou defeat the Northern Qi, reunifying the north.
581 Yang Jian overthrows the Northern Zhou and becomes the first Sui emperor.
583 The Emperor moves to a new capital, Daxing, built next to Chang'an to provide more room (although the two quickly become synonymous).
587 Emperor Wen summons the Western Liang emperor to Chang'an, and sends an army to protect Jiangling, but the populace surrenders to the Chen when they mistake their motives. Wen then siezes the territory, ending the Western Liang dynasty.
588-9 The Sui attack the Chen from many places along the Yangtsi at once, and finally enter Jiangkang, which surrenders. The city is razed to the ground. Chen nobles are escorted back to the north.
604 Emperor Yang designates Luoyang as the eastern Sui capital, although Chang'an remains the main capital.
608 The Tiele tribes attack Tuyuhun, but Murong Fuyun, the Tuyuhun chief, decides not to submit to Sui. Sui general Yuwen siezes many Tuyuhun people and then Tuyuhun territory, establishing four commanderies to be populated with exiles.
609 Murong Fuyun is forced to flee to the Dangxiang tribes.
610 Jiangdu's status is elevated to that of third capital.
Sui Dynasty, Wikipedia
It's not clear to me why the empire doesn't include large parts of Guizhou and Guangxi.
View the SVG only