The funeral march may have been heard about 13 thousand times because of casualties among the invading troops and perhaps twice as much for the deaths of the defeated country: that was the deadly conflict between the United States and Mexico between 1846 and 1848. Fallen in action or victims of hunger, thirst or various diseases, these soldiers were part of various armies in which voluntary fighters coexisted with professionals, elite officers with poor devils who imagined no future other than getting ready to escape misery, and even guerrillas who spontaneously confronted the enemy; As if that were not enough, thousands of Mexican civilians were also killed, sometimes because of the fire of the fighting, or because of the lack of food. Peter Guardino traces in this work the social history and not only politics of a war that marked forever the relationship between these two North American countries. His detailed analysis - in which there is a constant look at the aspects of gender, race and religion - allows us to confront the deep-rooted belief that Mexico was defeated because its population lacked a strong national feeling and postulated that the main explanations for the outcome were the American expansionism and the economic disparity of the contenders. This new approach to the traumatic clash of Mexico with its then much admired northern neighbor will undoubtedly revitalize the understanding of a key moment in our history.