Excerpts from Books and Wikipedia
"But in the tenth century, Annam had broken away from its Chinese overlords and claimed the right to rule itself: not as Annam, a Chinese province, but as Dai Viet, an independent kingdom ruled by the Ly dynasty of kings. . . . Ten centuries of Chinese domination had woven Chinese ways into the fabric of Dai Viet, and neither Song weakness nor Dai Viet independence could unpick it. The 1076 invasion ended with a border agreement between the two courts; it drew a line between China and Dai Viet, north of the Dai Viet capital Thang Long, that still exists today. But the border did not wall the Dai Viet away from the influence of the Song. The Ly kings, like their Chinese counterparts, were builders of Buddhist pagodas and benefactors of Buddhist monasteries. Chinese was still used in all court business; would-be officials still had to pass the Chinese civil service examination, based on the teachings of Confucius. And even as the Song court fled from the cradle of ancient Chinese civilization, the Ly dynasty adopted the Mandate of Heaven as its own. Their kings were “Southern Emperors,” ruling the “Southern Kingdoms” by virtue of their own, southern, celestial mandate;"