This thesis analyzes the progress in inter-state security cooperation among Argentina, Brazil, and Chile (ABC) since 1983 as a consequence of these states' political democratization, economic liberalization, and sub-regional integration. The causal role of each of these variables has varied over time. Argentina's political democratization in 1983, followed by democratic transitions in Brazil in 1985 and Chile in 1990, ushered in security cooperation, ending a century-long phase of interstate rivalry ...