During his government (1919)(1920)(1921)(1922)(1923)(1924)(1925)(1926)(1927)(1928)(1929)(1930), Leguía was not only interested in the internal politics, but also in the external politics, focusing on the border situation with Chile, Colombia and Ecuador.He achieved his goals in the first two cases, but he could only start with the last one.In the case of Colombia, borders were defined through direct negotiation between.President Leguía and the Colombian Ambassador in Peru, Lozano, which resulted in the 1922 Treaty.This caused the rejection of Peruvian population, given the secrecy of its content and elaboration, as well as the territories given to Colombia.This situation caused the Leticia Incident, at the area that would be given to Colombia, which led to an amendment of the 1922.Treaty through the Rio protocol (1934).In this work, under the perspective of foreign politics and Peruvian history, Leguía's government will be analyzed in terms of its contribution towards borders definition between Peru and Colombia in 1922, as well as the way in which this process took place to establish the territorial definition between both countries, which in turn implied giving the Amazonian Trapeze to Colombia and, therefore, the access to the Amazon River to Colombia.It will also analyze the meaning that this negotiation has in the field of foreign politics and the history of the borders of Peru.