Until the nineteenth century, the relationship between China and Vietnam was largely unaffected by third-party relationships, and it was managed within a common cultural framework. The greater firepower of Western imperialism and its interest in transformative domination destroyed the traditional context of the relationship. Asymmetry and its effects did not disappear. Both China and Vietnam were clearly in asymmetric relations with the West, and the military and cultural disjunction reduced the relationship to a physical collision of unequal capacities. China and Vietnam related to Western imperialism as the earth might relate to the impact of a large asteroid. The Western impact was a different kind of shock for China than it was for Vietnam, because for the first time in China's civilizational memory it was not the center of its world. From its experiences with nomadic groups, China was accustomed to occasional relative weakness, but it was not accustomed to relative insignificance. For Vietnam, the traditions of patriotic resistance to the Chinese could be re-targeted toward France, as could opportunistic habits of learning from and collaborating with the powerful.

Distracted from their mutual differences and sharing similar burdens of oppression, China and Vietnam moved from a face-to-face relationship to a shoulder-to-shoulder one. For the first time Vietnam faced an international challenge more important than China, and for the first time China had to face a world that laughed at its presumptions of centricity.