Ecuadorian – Peruvian War The Ecuadorian – Peruvian War , also known as the War of ' 41 ( ) , was a border war fought from July 5 – 31 , 1941 . It was the first of three military conflicts that occurred between these two South American nations during the 20th century . During the war , Peru occupied the western Ecuador ian province of El Oro and parts of the Andean province of Loja . Although the Ecuadorian – Peruvian War while World War II was ongoing , the Ecuadorian – Peruvian War was not related to World War II , and neither Ecuador norPeru were part of the Allied Powers nor Axis Powers . None of the states of Allied Powers or Axis Powers entered the war nor supported either Ecuador nor Peru . A cease - fire agreement between the two countries went into effect on July 31 , 1941 . Both countries signed the Protocolo de Río de Janeiro on January 29 , 1942 , and Peruvian forces subsequently withdrew . The enmity over the territorial dispute continued after 1942 and concluded following the Cenepa War of 1995 and the signing of the Brasilia Presidential Act peace agreement in October , 1998 . History . Background . The dispute between Ecuador and Peru dates from 1840 . It revolved around whether Ecuador ' s territory extended beyond the Andes mountain range to the Marañon ( Amazon ) river , including the Amazonian basin . As early as 1829 , Peru fought against the Gran Colombia ( a large loose state encompassing most of northern South America ) , of which the disputed lands were a part . After a series of battles , the war ended in what is known as the Battle of Tarqui ( or " Portete de Tarqui " ) . The Gual - Larrea Treaty was signed on September 22 , 1829 ending the war . This treaty , better known as the Treaty of Guayaquil , specified that the Gran Colombian - Peruvian border was to be the same border that had existed between the Spanish colonial viceroyalties of Nueva Granada and Lima . Subsequently , Ecuador contended that the Pedemonte - Mosquera Protocol was signed in 1830 as a continuation of the Gual - Larrea Treaty . Peru disputes the validity of this and even questions its existence , since the original document cannot be found . Furthermore , Peru argues that the treaties signed with the Gran Colombia were rendered void upon the dissolution of that federation . During 1859 and 1860 , the two countries fought over disputed territory bordering the Amazon . However , Ecuador was in a civil war that prevented diplomatic relations with the rest of Latin America , including Peruvian President Ramón Castilla . In 1887 , a treaty signed by both nations established that the King of Spain would act as an arbitrator . The resulting Herrera - García Treaty was expected to resolve the conflict permanently . However , the Parliament of Peru would only ratify the treaty after introducing modifications . Ecuador then withdrew from the process in protest of the Peruvian modifications , and the king abstained from issuing a decision . Salomón – Lozano Treaty . Another dispute was created after the signing of the Salomón – Lozano Treaty in March 1922 by the governments of Colombia and Peru , which at that time was ruled by Augusto B . Leguía . The treaty , which was kept secret , set the boundary between Peru and Colombia to be the Putumayo River , with the exception of a small strip of land controlled by the city of Leticia that would connect Colombia to the main flow of the Amazon River . Along with that , Colombia effectively recognized Peruvian control of the rest of the disputed region south of the Putumayo River . Following the coup d ' état of Leguía by the troops under the command of Luis Miguel Sánchez Cerro , the treaty was made public and caused much anger to the Peruvian population which deemed that the treaty awarded Colombia a section of Peruvian territory . This dispute over the Amazon region controlled by the city of Leticia would eventually cause a short war between Colombia and Peru between 1932 and 1933 . The conflict over Leticia , which was populated by both Peruvian and Colombian colonists , was resolved after Sanchez Cerro was assassinated and the new Peruvian president Óscar R . Benavides accepted the Rio de Janeiro Protocol which upheld the Salomón – Lozano Treaty and finally put an end to the border disputes between Colombia and Peru . The Salomón – Lozano Treaty was unpopular in Ecuador as well , which found itself surrounded on the east by Peru , which claimed the territory as an integral part of its Republic . Further adding to Ecuador ' s problems , now Colombian authorities also recognized Peru ' s territorial aspirations as legitimate . Preparing for war . An agreement was signed in 1936 which recognized territories in " de facto " possession by each country . The resulting border is known as the 1936 " status quo " border line . However , by 1938 both nations were once again holding minor border skirmishes . That same year , the entire Ecuadorian Cabinet , which was composed of high ranking army officers who served as advisors for General Alberto Enríquez Gallo ( who had taken charge of government after a military " coup d ' état " ) , resigned from government in order to take command of the Ecuadorian Army . Meanwhile , in Quito , there were public demonstrations of people chanting " " Down With Peru ! Long Live Ecuador ! " . " Peru ' s response to the events taking place in Ecuador was provided by foreign minister Carlos Concha , who stated , " " In Peru we have not yet lost our heads . Our country is in a process of prosperous development and the Government heads would have to be completely mad to think of war . " " The social situation of Peru at that time was undergoing major changes , with the social reforms begun by president Augusto B . Leguia ( which were aimed at improving roads , sanitation , industrial development , and promoting the general welfare of Peru ' s Native American population ) being continued by president General Oscar Benavides . Economically , Peru claimed to be attempting to run on a balanced budget , but Peru still held a large debt despite its positive foreign trade . However , despite these claims , Peru also began to mobilize its troops to its border with Ecuador in order to match the Ecuadorian troops which had been deployed to the dispute zone . On January 11 , 1941 , alleging that the Ecuadorians had been staging incursions and even occupations of the Peruvian territory of Zarumilla , the President of Peru , Manuel Prado , ordered the formation of the " North Grouping " , a military unit in charge of the " Northern Operational Theater " . Forces involved . Ecuador . According to the testimony of Col . Luis Rodríguez , the Ecuadorian forces at the disposal of the Army Border Command in El Oro ( Lieutenant Colonel Octavio A . Ochoa ) after the incidents of July 5 and 6 were as follows : Peru . As a result of the rising tensions on the border during 1939 and 1940 , the Peruvian President Manuel Prado authorized in December 1940 the creation of the " Agrupamiento del Norte " ( Northern Army Detachment ) . By July 1941 , this unit was ready to begin active military operations . Peruvian order of battle . Order of Battle , " Agrupamiento del Norte " , July 1941 Figures for total strength of the " Agrupamiento del Norte " at the beginning of offensive operations have been put at 11 , 500 to 13 , 000 men . War . The accounts as to which side fired the first shot vary considerably to this day . According to Peru ' s version Ecuadorian troops invaded Peruvian territory in the Zarumilla province , which started a battle that spread to a zone known as " Quebrada Seca " ( dry creek ) . But Ecuador ' s version is that Peru took a series of incidents between border patrols as a pretext to invade Ecuador , with the intention of forcing it to sign a clear border agreement . They argue that the clear disparity of military presence in the region between the two countries supports this version . The first clashes occurred on Saturday , July 5 , 1941 . According to Peruvian accounts , some Ecuadorian troops from the garrison of Huaquillas , a town on the bank of the Zarumilla river , which then served as the " status quo " line in the extreme left of the Ecuadorian - Peruvian border , crossed into the Peruvian border post at Aguas Verdes , a town directly in front of Huaquillas , and opened fire on a Peruvian patrol . These troops were then followed by some 200 Ecuadorian armed men , which attacked the Police station at Aguas Verdes , to which the Peruvians reacted by sending an infantry company to Aguas Verdes and repulsing the Ecuadorians back across the Zarumilla . The fighting then spread to the entire border area along the Zarumilla river . By July 6 , the Peruvian aviation was conducting air - strikes against the Ecuadorian border posts along the river . According to Ecuadorian Col . Luis A . Rodríguez , commander of the Ecuadorian forces defending El Oro during the war , the incidents of July 5 started when an Ecuadorian border patrol found some Peruvian civilians , protected by policemen , clearing a patch of land on the Ecuadorian side of the river . Upon seeing the patrol , the Peruvian policemen opened fire , killing one soldier . This was followed by the widespread exchange of fire between troops on the opposing banks of the Zarumilla , while two Ecuadorian officers sent to Aguas Verdes to speak with the Peruvian local commanding officer were told by Peruvian authorities to go back to their lines . Regardless , the much larger and better equipped Peruvian force of 13 , 000 men quickly overwhelmed the approximately 1 , 800 Ecuadorian covering forces , driving them back from the Zarumilla and invading the Ecuadorian province of El Oro . Peru also carried out limited aerial bombing of the Ecuadorian towns of Huaquillas , Arenillas , Santa Rosa , and Machala . The Peruvian army had at its disposal a battalion of armor made up of Czech tanks , with artillery and air support . They had also established a paratroop unit in the region and used it to great effect by seizing the Ecuadorian port city of Puerto Bolívar , on July 27 , 1941 , marking the first time in the Americas that airborne troops were use in combat . Faced with a delicate political situation that even prompted Ecuadorian President Carlos Alberto Arroyo del Río to keep a sizable part of the Army in the capital , Quito , Ecuador promptly requested a cease - fire , which went into effect on July 31 , 1941 . Yet , Ecuador still carried out guerrilla attacks upon the Peruvian troops . As a result of the war , Peru occupied almost the entire Ecuadorian coastal province of El Oro and some towns of the Andean province of Loja , besides driving the Ecuadorians back along the whole line of dispute along the Amazonian border . Ecuador ' s government , led by Doctor Carlos Alberto Arroyo del Río , signed the " Protocolo de Río de Janeiro " on January 29 , 1942 , and Peruvian forces subsequently withdrew . Nonetheless , during the retreat several attacks were made against the Peruvian military , and a series of lives were lost during the process . Aftermath . The placement of the border markers along the definitive border line indicated by the Rio Protocol was not concluded when the Ecuadorians withdrew from the demarcation commissions in 1948 , arguing inconsistencies between the geographical realities on the ground and the instructions of the Protocol , a situation that according to Ecuador made it impossible to implement the Protocol until Peru agreed to negotiate a proper line in the affected area . Thus , some 78 km of the Ecuadorian - Peruvian border were left unmarked for the next fifty years , causing continuous diplomatic and military crisis between the two countries . In 1960 , Ecuadorian President José María Velasco declared that the Rio Protocol was " void " . According to the Velasco Administration , the treaty , having been signed under Peruvian military occupation of Ecuadorian soil , was illegal and contrary to Panamerican treaties that outlawed any treaty signed under the threat of force . However , this proclamation made little international impact ( the treaty was still held as valid by Peru and four more countries ) . Peruvian analysts have speculated that President Velasco used the " nullity thesis " in order to gather political support with a nationalistic and populist rhetoric . In 1981 , both countries again clashed briefly in the Paquisha War . Only in the aftermath of the Cenepa War of 1995 was the dispute finally settled . On October 26 , 1998 , representatives of Peru and Ecuador signed a definitive peace agreement ( Brasilia Presidential Act ) . Notable combatants . Peru :