Vietnamese identity is defined by the region-attachment , it isn’t a region that is strictly set of territorial boundaries, but instead, it is the rough notion that came from the ancient time, which has been described by different names throughout the history, for example, one of them is “ The River and Mountains of the Southern Country ”(Nam quốc sơn hà). And from it to expand outward, an expansion through either massive migration or political invasion, which then shaped the entire heartland of the Vietnamese people.
Vietnamese identity is expressed to be “a nation of survival”, dân tộc sinh tồn . To survive from fighting against outer invasion and to survive from environmental challenges. The desire to survive is the ground of Vietnamese culture, it generates the habit to adapt new things, whether from the invaders or from the new environment(places that they move to), and thus, as a result, Vietnamese culture is ongoingly evolving itself, it belongs to the model of cultural pluralism rather than a part of any single cultural sphere.
Survival is an avoidable fact, and the Vietnamese-ness is sensitive of keeping this fact psychologically.