Indochina played a pioneering role during the decolonization of the French empire, and the religious issue proved important to the process. Even to this day, state-church relations bear signs of this contentious and painful past. The historiography of the Indochina War, as well as that of the Vietnam War, clearly call attention to the activism of religious leaders and religious communities, especially Buddhists and Catholics, who fought for independence, peace, and the needs and rights of the Third World. And religion was put to the service of shaping public opinion both in Vietnam and internationally. Naturally, ideological convictions during the era of decolonialization account for the dominance of political analysis of this subject. But with the passage of time we can now develop a more sociological understanding of people's religious motivations and practices and the role they played in the conflict between communism and nationalism. The historian can also re-examine the secularization process in decolonized societies by analyzing, on the one hand, the supposed loss of ascendancy of religions in society and, on the other hand, the appearance of new religious movements that tended to adapt to modernity. This essay explores these politico-religious dynamics in the context of the decolonization of Vietnam.