This project explores the military and political mobilization of rural and urban working sectors of Puerto Rican society as the Island transitioned from Spanish to U.S. imperial rule. In particular, my research is interested in examining how this shift occurs via patterns of inclusion-exclusion within the military and the various forms of citizenship that are subsequently transformed into socio-economic and political enfranchisement. Analyzing the armed forces as a culture-homogenizing agent helps to explain the formation and evolution of Puerto Rican national identities from 1868 to 1952, and how these evolving identities affected the political choices of the Island. This phenomenon, I argue, led to the creation of the Estado Libre Asociado in 1952. The role played by the tens of thousands of Puerto Ricans in the metropolitan military in the final creation of a populist project taking place under colonial rule in the Island was threefold. Firstly, these soldiers served as political leverage during WWII to speed up the decolonization process. Secondly, they incarnated the commonwealth ideology by fighting and dying in the Korean War. Finally, the Puerto Rican soldiers filled the ranks of the army of technicians and technocrats attempting to fulfill the promises of a modern industrial Puerto Rico after the returned from the wars. In contrast to Puerto Rican popular national mythology and mainstream academic discourse that has marginalized the agency of subaltern groups; I argue that the Puerto Rican soldier was neither cannon fodder for the metropolis nor the pawn of the Creole political elites. Regaining their masculinity, upward mobility, and political enfranchisement were among some of the incentives enticing the Puerto Rican peasant into military service. The enfranchisement of subaltern sectors via military service ultimately created a very liberal, popular, and broad definition of Puerto Rico’s national identity. When the Puerto Rican peasant/soldier became the embodiment of the Commonwealth formula, the political leaders involved in its design were in fact responding to these soldiers’ complex identities, which among other things compelled them to defend the “American Nation” to show their Puertorriqueñidad.