Why do leaders choose to drastically alter their state’s international behavior? This article aims to identify common domestic and international conditions that led to a foreign policy shift (FPS). Given the difficulty associated with defining and measuring an FPS, this study advances a replicable and theoretically informed definition to guide case selection. This avoids both the type of selection bias evident in many previous qualitative analyses and the use of measurements that are not closely related to the concept as in preceding quantitative research designs. The subsequent historical analysis of FPSs in Latin America and the Caribbean between 1945 and 2008 identifies two causal paths that led to FPS. By one account, growing discontent with longstanding dictatorships led to political polarization and subsequent succession crises, including civil wars and/or international military intervention, from
which new regimes/leaders emerged. By another, international isolation worsened economic conditions, causing leaders to implement administrative reforms to alter their foreign policy by conceding to pressures from major powers.