During the Second World War, the FDR administration placed the FBI in charge of political surveillance in Latin America. Through a program called the Special Intelligence Service (SIS), 700 agents were assigned to combat Nazi influence in Mexico, Brazil, Chile, and Argentina. The SIS's mission, however, extended beyond countries with significant German populations or Nazi spy rings. As evidence of the SIS's overreach, forty-five agents were dispatched to Ecuador, a country without any German espionage networks. Furthermore, by 1943, FBI director J. Edgar Hoover shifted the SIS's focus from Nazism to communism. Marc Becker interrogates a trove of FBI documents from its Ecuador mission to uncover the history and purpose of the SIS's intervention in Latin America and for the light they shed on leftist organizing efforts in Latin America. Ultimately, the FBI's activities reveal the sustained nature of US imperial ambitions in the Americas.