In the early 1960s, Vietnamese resistance to US aggression galvanized a generation of activists, prompting the French in particular to forge an international antiwar alliance with their peers across Western Europe and North America, especially the United States. Together, they came to believe that the Vietnam War was caused by a broader “system” that made such wars possible in the first place. Searching for a way to not only explain this system, but overthrow it, they increasingly turned to Leninism. Radicals in the North Atlantic named the system imperialism, defined their internationalism as anti-imperialism, and called for a coordinated worldwide revolution based in the principle of the right of nations to self-determination. Following the lead of African American, Latin American, and Vietnamese revolutionaries, they argued that the best way to combat this imperialist system was to open new fronts inside the imperialist centers, triggering a wave of domestic upheaval that reached new heights in May 1968. But when this anti-imperialist front faced state repression and imprisonment in France, the United States, and South Vietnam, these same radicals began to advocate individual rights alongside anti-imperialist revolution in the early 1970s. In so doing, they lent legitimacy to a competing form of internationalism that shared the progressive aspirations of Leninist anti-imperialism but rejected nationalism in favor of human rights. When genocide, internecine war, and refugee crises in Southeast Asia eroded faith in national self-determination in the late 1970s, former French radicals sided with the US government in a global movement championing human rights against the sovereignty of states like Vietnam.