This dissertation explores the obstacles for US formal military bases in Latin America. While in the past, the United States managed to establish bases in several countries in the region, despite Washingtons efforts every negotiation to open new bases has failed since 2000, and older bases have been terminated, as in the case of Ecuador. Using evidence from Ecuador, Colombia, El Salvador, and other countries in the region, the dissertation finds that shifts in government preferences do not explain this failure. Instead, domestic challenges to host governments in Latin America systematically appear as blocking mechanisms that impede the establishment of foreign military bases, even when leaders support them.The dissertation builds on the work of Alexander Cooley and others and develops a model of base politics to explain how domestic political calculations affect foreign basing negotiations. Furthermore, the dissertation finds that when formal bases have not succeeded, interested governments have worked around domestic constrains to establish alternative and informal arrangements that allow US military presence and operations in their countries. These alternative arrangements, or quasi-bases, have advanced US security interests in Latin America even in the absence of formal base leases, while at the same time their secrecy and informality protects Latin American leaders from domestic contestation. iii ACKNOWLEDGEMENTS This dissertation would not have been possible without the guidance of my chair, Patrick Jackson, and the thorough comments of Arlene Tickner and Eric Hershberg, members of my committee. Through over a year of revising the final manuscript it gained a lot both in content and in clarity, thanks to the several rounds of revisions where the three of them contributed from their different fields of expertise. Other people at the American University provided guidance, suggestions, source material, and more importantly, constant support. Ryan Briggs and Tom Long have been patient readers of my work and provided valuable criticism during every stage of this process. But more than anything, their friendship and moral support has been the greatest gift I received during my time at American University. Dean Louis Goodman, Sharon Weiner, Philip Brenner, and my cohort at the SIS PhD program have also been constant sources of wisdom and support and I cannot thank them enough. Back in Colombia, the faculty at the School of Government of the Universidad de los Andes blessed me with their confidence and always provided a warm space for me to work when I visited Bogota. Carlos Caballero Argaez, Director of the School, and Carlos Angulo, then President of the University, both encouraged me and provided everything I could need to start, and complete, my PhD successfully. This dissertation greatly benefited from comments I received from Alexander Cooley, David Vine, the faculty at the Universidade de Sao Paulo, along with reviewers and commentators of pieces presented at various academic conferences. Maria Berger also co...