The present work is an historical representation on the structure, the running and the transformations of the Military Force of the second half of the 19th century, especially during the period between 1857 and 1885, in Colombia, and a study of its administrative aspects through the follow-up of the constitutional or legal form.Its legal existence throughout that period is emphasized in particular, since its existence has been questioned due to the conditions and characteristics the Military Force had during the 19th century, as it went from being a bastion of pride and defense to being a body of discussed institutional framework, due to the lack of uniformity in its decisions and advances.It also appeared as a body without professionalism and its decentralized condition made it difficult for it to develop solid and congruent policies.This work helps understand the effects that the federal experience had in the national institutions, especially the military, showing, once again, that the irregularity of the budget and the subordination of the military to the civilian power, generated the greatest contradictions for the military force.Nevertheless, such experiment was useful to demonstrate how necessary the presence of Public Force was because in spite of the disadvantages of the time, with liberal doctrines taken to the extreme, the institution managed to stay, moderately, until its Military Reform took place.