In the first three millennia of their relationship, China and Vietnam have been through almost every conceivable pattern of interaction among neighbors. Even in the past fifty years, the relationship has swung from intimate friendship to implacable enmity, and at each extreme the Sino-Vietnamese relationship became the defining relationship for different phases of Southeast Asian regional politics and a major element of global international relations. Although the success of normalization since 1991 has taken the relationship out of world headlines, the stability of relations between China and Vietnam remains an essential part of the foundation of international order in Asia.

The one constant in relations between China and Vietnam since the unification of the Chinese empire in 221 bc has been that China is always much the larger partner. Regardless of whether the relationship was hostile, friendly, or in between, it has been asymmetric. China has always been a much more important presence for Vietnam than Vietnam has been for China, and Vietnam has had a more acute sense of the risks and opportunities offered by the relationship. Given the great disparity between China and Vietnam, one might expect that either Vietnam would be subservient to China or that China would annex Vietnam. In fact, however, even though Vietnam was formally a part of China for a millennium it was never fully “domesticated,” and for most of the last thousand years the relationship has been a negotiated one.