The introduction presents the main arguments that will be developed in the book and how letters and petitions that were found in the military archive are the basis from which to argue that the military was an institution in the first half of the nineteenth century. The nearly one thousand case studies provide the information that makes it possible to understand the Peruvian armed forces. This chapter also covers the historiographical debate by discussing the notion of caudillos and how although most of the new republics have been seen as controlled by armed men on horseback, the military can be described as an insitution that while having a colonial origin, transformed throughout the wars of independence. The way in which those who became members of the armed forces is analyzed in detail showing that a social system of protection for those who were part of it developed from the colonial systems Comparisons are made with the cases of the United States, France, Spain and the rest of Latin America. This section ends with a description of the book’s structure and a description of each chapter.