Between October 1965 and March 1966, the Indonesian army and allied militias killed approximately one million people accused of communist sympathies, one of the twentieth century's largest mass killings. Vincent Bevins reveals how the United States and United Kingdom supported this violence and how its success inspired similar programs across the developing world. Indonesia's Communist Party was the largest outside the Soviet Union and China, and its destruction without direct Western military intervention seemed to prove that anticommunist terror could work. Bevins, a journalist who covered Latin America and Southeast Asia, traces connections between Jakarta and the coups and killings in Brazil, Chile, Argentina, and elsewhere. The method was consistent: identify leftists through lists, mobilize paramilitaries and death squads, kill without accountability, and install governments friendly to Western capital. The perpetrators were often trained by the United States and protected by American diplomatic cover. Bevins interviews survivors in Indonesia, Brazil, and Chile, bringing human scale to events often reduced to Cold War abstractions. He examines how the massacres shaped subsequent history, not only in the countries where they occurred but in the cautionary message they sent to leftist movements worldwide. The book asks uncomfortable questions about American complicity in mass violence and challenges narratives that frame the Cold War as a struggle between freedom and tyranny.