In late October 1964, nearly 1,000 European and U.S. citizens were taken hostage by rebel forces in Stanleyville in northern Congo as part of an attempt to create the “People’s Republic of Congo,” an opposition regime designed to rival the pro-Western government in the capital Léopoldville (now Kinshasa). The hostages were captured to use as leverage against the advancing Armée Nationale Congolaise (ANC), led by white mercenaries as part of a Western-backed military effort to crush the rebellion. In response, Belgium and the United States launched a military intervention to rescue their citizens on 24 November 1964, publicly justifying the incursion on humanitarian grounds. In reality, the main purpose was to crush the rebellion and secure Western interests in Congo. The intervention reflected a cavalier attitude toward sovereignty, international law, and the use of force in postcolonial Africa and had the adverse effect of discrediting humanitarian reasoning as a basis for military intervention until the end of the Cold War. The massacre of tens of thousands of Congolese in Stanleyville was a unique moment in which African countries united in their criticism of Western policies and demanded firmer sovereignty in the postcolonial world.