In April 1965, the Dominican Republic was the scene of the first US military intervention in Latin America since the Cuban Revolution, challenging the region's autonomy. For Chile, this episode tested the foreign policy of Eduardo Frei Montalva, who advocated a "dignified partnership" with Washington against the backdrop of the Alliance for Progress. Drawing on previously unpublished archives, declassified documents, and interviews, this book reconstructs Chile's response to the Dominican crisis. It analyzes the tensions between pragmatism and principles in the Frei administration, Chile's room for maneuver, and its role in the Organization of American States (OAS) versus the Inter-American Peace Force (IAP). More than an isolated incident, this case reflects the limits of a mid-level country in an inter-American system dominated by the United States. Chilean diplomacy, caught between external pressures and internal balances, began a progressive distancing from Washington, with implications for its foreign policy in the following years. "They may gain an island, but they will lose a continent" is a key study of the dilemmas of Chilean foreign policy in the midst of the Cold War.