On September 1, 1932, over 300 armed Peruvian civilians seized the Amazonian harbor town of Leticia in a demonstration against the Salomón-Lozano Treaty of 1922 which ceded the territory to Colombia. In response, the Colombian government announced plans to send a force of 1,500 soldiers to repel the invaders. Upon learning of Colombia's intent, the Peruvian government--which had earlier criticized the invaders' action--moved to support its nationals. The first skirmishes took place in early 1933, as the Colombian river fleet made its way up the Amazon to the site of the invasion. After months of diplomatic wrangling over the selection of a mutually acceptable forum for the peaceful resolution of the dispute, Colombia and Peru accepted mediation by the League of Nations. A provisional peace agreement, signed in May 1933, provided for the league to assume control of the disputed territory while bilateral negotiations proceeded.
In June 1934, following the signing in May of yet another bilateral treaty, Leticia was returned to Colombia. Under the terms of the May pact, Peruvian concessions included a formal apology for the 1932 invasion and a reaffirmation of Peru's acceptance of the 1922 agreement. The treaty also provided for demilitarization of the area around Leticia, free navigation on the Amazon and Río Putumayo, and a pledge of non-aggression. As a gesture of mutual goodwill in continuing bilateral cooperation, the settlement also provided for future negotiations on trade and tariff issues, riverine transport, population settlements in the region, and the joint policing of the common border. In September 1935, the instruments of ratification were exchanged.