For most of the period from 111 BC to the early 10th century AD Vietnam was under the rule of successive Chinese dynasties. Sporadic independence movements were attempted, but were quickly suppressed by Chinese forces. In 939 AD the Vietnamese defeated Chinese forces at the Bach Dang River and finally gained independence after 10 centuries under Chinese control. They gained complete autonomy a century later.
China's conquest had arrested the independent evoluation of one of the earliest Southeast Asian polities. Imperial Chinese policy had been to assimilate the Vietnamese and implant Chinese values, customs and institutions. But while the Vietnamese did indeed adopt enough of these patterns and while Chinese influence on Vietnamese history had not been entirely negative, the Vietnamese sustained a hatred of Chinese rule and resisted cultural genocide for 1000 years. It's an astonishing display of national pride and determination practically unparalleled in world history, as expressed by Lockard (1995). Some historians have noted an ancient and perhaps unprecedented sense of nationhood that facilitated resistance to absorption, as one put it:
"The Vietnamese will to independence was too strong to permit it; and that will to independence could never have existed without some intuition, reaching through all social classes right down to the seemingly crustacean politics of the bamboo-walled villages, that there was a special Vietnamese collective identity of some sort. The Vietnamese nation is, to put it bluntly, one of the longeest enduring acts of faith in human history."
Very powerful words indeed for a nation that has been attacked, conquered, and colonized successively by the Chinese, the Mongols, the French, the Japanese, and the Americans.
Reference:
Lockard, C. A. (1995). Integrating Southeast Asian into the framework of world history: The period before 1500. The History Teacher, 29(1), 7-35.