The article aims to investigate the Colombo-Peruvian War, also known in Brazilian history as the Letician Question, a conflict between the years 1932 and 1934, of which Brazil was an arbiter in the process of restoring peace and served as part of the Commission entrusted with ensuring the execution of special agreements, through the diplomatic activities of Division General Cândido Mariano da Silva Rondon. Focusing on the New Military History, the research was based on the documentation produced by the Army in the period. Thus, we analyze the historical role of this State institution destined to the exercise of violence, that is, as an instrument of war and, added to this dimension, we examine the border tensions surrounding the historical occupation of the territories involved. [ABSTRACT FROM AUTHOR]