Paraguayan War The Paraguayan War was the largest international armed conflict occurred in South America . It was fought between the Paraguay and Triple Alliance , composed of Brazil , Argentina and Uruguay . The war lasted from December of 1864 to March of 1870 and caused approximately 390 , 000 deaths . It is also called the War of the Triple Alliance ( " Guerra de la Triple Alianza " ) , Argentina and Uruguay , and the Great War in Paraguay . Some older sources call the War the Lopez War , though this clearly indicates a point of view on the part of such authors . The conflict began with the invasion of Brazilian province of Mato Grosso by the Paraguayan army under orders from president Francisco Solano López . The attack occurred after Brazil ' s armed intervention in Uruguay in 1864 that ended the civil war to overthrow the Uruguayan president Atanasio Aguirre of the Blanco Party , and install his rival Colorado , Venancio Flores . Solano López feared that the Empire of Brazil and Argentina were threatening to dismantle the smaller countries of Southern Cone . To confront the perceived threat , Solano Lopez hoped to have the support of the Blancos , Uruguay , and warlords ( " caudillos " ) of northern Argentina . The fear of the Paraguayan president prompted him on November 11 , 1865 to seize the Brazilian steamship " Marques de Olinda " , carrying the governor of the province of Mato Grosso . The Paraguayan government suspected that the steamer was also carrying a cargo of weapons . Six weeks later , the Paraguayans invaded Mato Grosso . Before the Brazilian intervention in Uruguay , Solano López was already buying modern military equipment in preparation for a future conflict . Brazil , Argentina and Uruguay , the Allies , defeated Paraguay after more than five years of struggle during which the Brazil sent around 150 , 000 men to war . Roughly 5 , 000 , 000 did not return - some authors assert that the deaths in the case of Brazil may have reached 600 , 000 if one includes civilians mainly in the provinces of Rio Grande do Sul and Mato Grosso . Argentina and Uruguay suffered heavy losses in proportion - more than 50 % of their troops died during the war - although in absolute numbers it was less significant . As for the human losses suffered by Paraguay , Are estimated at up to 300 , 000 people , civilians and military , died due to fighting , epidemics that raged during the war , and famine . The defeat marked a turning point in history of Paraguay , Making it one of the most backward countries in South America due to a declining population , a nearly ten year long military occupation , and the payment of a heavy war indemnity , in the case of Brazil up to WWII , and loss of roughly 40 % of its territory to Brazil and Argentina . For decades after the War Paraguay remained under the hegemony of Brazil . It was the last of four international armed conflicts involving the countries of the River Plate region who fought Brazil in the nineteenth century for supremacy in South America . The first was the Argentina - Brazil War , The second Silver War , and the third War of Uruguay . Historiography of the war in Paraguay . The Historiography of the Paraguayan War has undergone profound changes since the outbreak of the conflict . During and after the war , the historians of the countries involved explained the cause as solely due to the excessive and expansionist ambition of Solano López . From the 1960s , a second current of historiography , more committed to the contemporary ideological struggle of the decade between capitalism and communism , and right and left , presented a version of the military conflict as motivated by the interests of the British Empire that sought at any cost to prevent the rise of any Latin American nation that was militarily and economically powerful . From the 1980s , new studies have proposed different reasons , proposing that the causes were due to processes of development of national states of the countries involved . This entry draws on recent research about the Paraguayan War conducted by professional historians , but also presents at certain points , for comparison , the claims of the other two previous historiographical trends that may be considered outdated ( traditional and revisionist ) . Causes of war . After the Platine War in 1852 ended with the victory of the Allies ( Unitarians Argentina , Uruguayan Colorados and Empire of Brazil ) against the Argentine Federalists and Uruguayan Blancos led by Juan Manuel Rosas , the Plata region was temporarily pacified . However , soon the rivalries between Argentina , Brazil , Uruguay and Paraguay came to the fore thanks to disagreements about the borders between countries , freedom of navigation on the rivers , the power struggles by the local parties ( Federalists and Unitarians in Argentina and Uruguay in the Blancos and Colorados ) and historic rivalries dating back more than three centuries . Historian Francisco Doratioto concludes : The Paraguayan War ( 1864 - 1870 ) . In retaliation for intervention in Uruguay , on November 11 of 1864 Francisco Solano Lopez ordered of the Brazilian Ship " Marques de Olinda " . At next day , the steamer Paraguay " Tacuari " arrest the ship Brazilian , who climbed the Paraguay River towards the then Province Mato Grosso , Carrying Colonel Frederico Carneiro de Campos , Newly named president of that province and the doctor Antonio Antunes da Luz , among others . The crew and passengers were taken prisoner and sent to prison , where everyone , without exception , have succumbed to starvation and ill treatment . Without loss of time , relations with Brazil were already broken and in December the southern Mato Grosso , Current Mato Grosso do Sul , Was raided , even before any formal declaration of war on Brazil , Which was only made on December 13 . Three months later , in March 18 of 1864 Lopez declared war on Argentina that required neutrality in the conflict and not allow the Paraguayan army to cross its territory to fight in Uruguay and southern Brazil invade . When news of events began to reach Dom Pedro II and his ministry in Rio de Janeiro , Capital of the Empire in March 1865 Solano López ' s troops penetrated Corrientes ( Argentina ) , For the Rio Grande do Sul and the Uruguay , Where he hoped to find support from " blancos " . The Uruguay , Already governed by Venancio Flores Installed by the Imperial Government of Brazil , sympathized with the Brazil and Argentina . First phase : Paraguayan offensive ( 1864 - 1865 ) . Invasion of the provinces of Mato Grosso , Corrientes and Rio Grande do Sul . During the first phase of the war ( 1864 - 1865 ) , The initiative was with the Paraguayans . The armies of López defined the three battlefronts initial invading Mato Grosso in December 1864 And , in early 1865 The Rio Grande do Sul and the Argentine province of Corrientes . Attacking , almost simultaneously in the north ( Mato Grosso ) and south ( Rio Grande and Corrientes ) , the Paraguayans have established two theaters . The invasion of Mato Grosso was made simultaneously by two bodies of Paraguayan troops . The province was almost unmanned military , and the numerical superiority of the invaders allowed them to make a quick campaign and successful . A detachment of five thousand men besides , transported in ten ships and commanded by Colonel Vicente Barros went up the Paraguay river and attacked the New Fort Coimbra . The garrison of 155 men resisted for three days , under the command of Lieutenant - Colonel Hermenegildo de Albuquerque Porto Carrero After baron of Fort Coimbra . When the munitions were exhausted the defenders abandoned the fort and withdrew up the river aboard the gunboat Anhambaí towards Corumbá . After occupying the empty fort the Paraguayans advanced north taking in January 1865 , the cities of Albuquerque and Corumbá . The second column Paraguayan , commanded by Colonel Francisco Isidoro Resquín and included four thousand men , penetrated the ground , in a region south of Mato Grosso , and sent a detachment to attack the military frontier of Dourados . The siege , led by Major Martin Urbieta ; encountered tough resistance on the part of Lieutenant Antônio Ribeiro Currently the patron of Table Auxiliary Officers , and his 16 companions , who died without yielding ( December 29 of 1864 ) . Attackers continued until Nioaque and Miranda , Defeating the troops of Colonel José Dias da Silva . then sent a detachment to Cushion Taken in April 1865 . The Paraguayan forces , despite their victories , not continued their march to Cuiabá , The capital of the province where the attack was even expected - John Manuel Leverger had fortified camp Melgaço to protect Cuiabá . The main objective of the invasion of Mato Grosso was diverting attention from the Brazilian government to northern Paraguay , where the decision of the war would take place in the south ( region closest to the River Plate estuary ) . It is what is called a diversion , intended to deceive the enemy . The invasion of Corrientes and Rio Grande do Sul was the second stage of the Paraguayan offensive . To raise the support Blancos in Uruguay , the Paraguayan forces had to go through Argentine territory . In March 1865 , López asked the Argentine government ' s permission for the army commanded by General Wenceslao Robles With about 25 000 men , crossed the province Corrientes . President Bartolomeu Mitre , An ally of Brazil and Uruguay in the intervention , denied him permission . In response to this denial , on March 18 of 1865 , Paraguay declared war on Argentina . On Friday April 13 of 1865 . A squadron five Paraguayan warships , down the Parana River imprisoned Argentine ships in the river port of Corrientes . Then the troops of General Robles took the city . By invading Corrientes , López thought to gain the support of powerful Argentine warlord General Justo José de Urquiza , Governor of the provinces of Corrientes and Entre Ríos , Head federalist hostile to Mitre and the government Buenos Aires . The invasion of Argentina for Lopez , however , had the opposite effect . Urquiza and other Argentines sympathized with the Federalists " blancos " Uruguayans . The assassination of General " blanco " Leandro Gómez by " Colorados " after their heroic defense of the attack Payssandú of Brazilians " Colorado " in January 1865 caused resentment in the Federalist Argentines . Lopez ' s actions gave the federalists Argentines only 2 ( two ) options : fight or remain neutral attacker . Urquiza , initially vowed to fight Lopez . The ambiguous attitude assumed by Urquiza , however , kept the Paraguayan troops , who advanced after about 200 km southward , ultimately ending the offensive . In joint action with the forces of Robles , a troop of ten thousand men under the command of Lieutenant - Colonel Antonio de la Cruz Estigarribia crossed the Argentine border south of Encarnación In May 1865 , Heading for Rio Grande do Sul traveled down Uruguay River upon the village of San Borja and took on June 12 . Uruguaiana Further south , was taken in August 5 without providing any significant resistance to the advancement of Paraguay . The first Brazilian reaction . Brazil ' s first reaction was to send an expedition to fight the invaders in Mato Grosso . A column of 2 , 780 men commanded by Colonel Pedro Manuel Drago left Uberaba In Minas Gerais In April 1865 And only reached Coxim in December of that year , after a difficult march of more than two thousand kilometers through four provinces . But he found Coxim already abandoned by the enemy . The same happened in Miranda , Where he arrived in September 1866 . In January 1867 Colonel Carlos de Morais Camisão assumed command of the column , reduced to 1 , 680 men , and decided to invade Paraguayan territory , which penetrated to Laguna In April . Pursued by cavalry enemy , the column was forced to withdraw , an action that became known as the withdrawal of Laguna . Despite the efforts of the column of Colonel Camisão and organized resistance by the provincial president , who succeeded in freeing Corumbá in June 1867 , invaded the region remained under the control of the Paraguayans . Only in April 1868 is that the invaders withdrew , moving troops to the main theater of operations in southern Paraguay . The Treaty of the Triple Aliance . On 1 . May of 1865Brazil , Argentina and Uruguay signed in Buenos Aires , Triple Alliance Treaty Against Paraguay . The military forces of the Triple Alliance were at the beginning of the war , well below those of Paraguay , which had over 60 000 men and a fleet of 23 steamers and five vessels suitable for inland waterways . Its artillery had about 400 guns . The troops assembled in Brazil , Argentina and Uruguay , ready to spring into action , could not reach one third of Paraguay . Argentina had about 8000 troops and a fleet of four steamers and a schooner . Uruguay entered the war with less than three thousand men and no navy . Of the 18 , 000 soldiers that Brazil could tell , only 8000 were already in its southern garrisons . The advantage of the Brazilians was in his navy : 42 ships with 939 fire hydrants and about four thousand men , well trained crew . And much of the fleet was already in the La Plata , where he had acted under the command of Marquis Tamandaré In the intervention against Aguirre . In fact , Brazil was unprepared to enter a war . Despite its immense territory and population density Brazil had an army ill - organized and very small . And indeed , this situation was a reflection of the organization of slave society , which , marginalizing the population free non - proprietary , difficult to form an army with a sense of responsibility , discipline and patriotism . Moreover , military service was seen as a punishment always be avoided and the recruitment was arbitrary and violent . The troops used in the interventions in Uruguay were composed primarily of the armed contingents of gaucho politicians and some of the effective National guard . A reinforcement was therefore necessary . The infantry Brazilian who fought in the War of Paraguay was not professional soldiers , but by so - called Volunteers from the Motherland Citizens who presented themselves to fight . Many slaves were sent by farmers . The cavalry was formed by National guard Rio Grande do Sul The Treaty of the Triple Alliance , the supreme command of Allied troops would be up to Bartolome Mitre , President of Argentina . And was in the first phase of the war . The Allies recapture Temporarily Corrientes . A small force of 3846 men under the command of General Wenceslao Paunero observed the activity of the enemy . Realizing that the Paraguayans had left Corrientes poorly protected when going to the east bank of the river , General Argentina embarked his troops , along with 364 Brazilians and 500 European mercenaries , in the Brazilian fleet , ascended the Rio Parana and , in May 25 ( The Argentine national holiday ) recaptured Corrientes after arduous struggle . López immediately sent troops to retake the city , while the troops were retreating raiders and maintained by Corriente less than 24 ( twenty four ) hours . The Allied victory , though ephemeral , served to raise morale . The attack also demonstrated the vulnerability of the López communication lines of his invading army . The Battle Of Riachuelo . It was in the naval sector that Brazil , better prepared , inflicted early in the first year of the war , a heavy defeat to Paraguay at the Battle of Riachuelo . In the bowl of River Plate communications were made by rivers , there were almost no roads . Whoever controlled the rivers would win the war . The Paraguayan fortifications had been built on the banks of the lower course ( part of the river near its mouth ) of the Paraguay River . In June 11 of 1865 in Parana River , Fought the Battle of Riachuelo , Where the squadron commanded by the chief of division Francisco Manuel Barroso da Silva defeated the Paraguayan fleet , commanded by Pedro Inacio Meza , Cutting off communications with the Paraguayan lieutenant colonel Antonio de la Cruz Estigarribia , Who was attacking Rio Grande do Sul . The victory of the Riachuelo had remarkable influence on the course of the war : stop the invasion of the Argentine province of Entre Ríos . Destroyed the Paraguayan Navy ( making it impossible the stay of the Paraguayans in Argentina ) and cut the march of the then triumphant López . She practically decided the war in favor of the Triple Alliance , which took control from then on , the rivers of the Plata Basin to the entrance of Paraguay . From that point until the final defeat , the country had to resort to defensive war . Paraguay Invades Rio Grande do Sul . Simultaneously with the naval attack , a force of 10 , 000 Paraguayans crossed the Argentine province of Missions . Reaching Uruguay River , The force split into two ( 2 ) columns and headed south , marching on both riverbanks . Lieutenant Colonel Antonio de la Cruz Estigarribia , The overall commander , led about 7 , 500 men on the east bank , and Major Pedro Duarte commanded 5 , 500 men on the west bank . The Paraguayans met little resistance on the west bank of the Argentines and the Brazilians on the east bank . Lopez believed that if he could control the Rio Grande do Sul invade and Uruguay , slaves Brazilians would revolt and the newly expelled " blancos " Uruguayans would again take up arms . In addition , Paraguayan emissaries incited sedition among the troops formed by irregular Urquiza in Entre Ríos . Urquiza , who had received the command of the vanguard ally , volunteered to return to the province and restore order . Instead , he returned to his ranch Increased his fortune by selling horses to the allies , and the irregular troops defected to their farms and ranches . Colonel Estigarribia crossed the Uruguay River and occupied successively from June to August , the settlements of San Borja , Itaqui and Uruguaiana . The contacts with Major Donnelly was interrupted by the harassment of two Brazilian armed vessels , commanded by Lieutenant Floriano Peixoto ( Later Marshal and the second president of Brazil ) And by marsh separating them . The Uruguayan president flores decided to attack the smallest of the Paraguayan forces . In August 17 In Battle of Jataí On the right bank of Uruguay River , The column under the command of Major Pedro Duarte , who wanted to get to Uruguay , was arrested by Flores . Second Phase : Allied Couter Atack . Surrender of Uruguaiana and Retreat of paraguayan Troops . In July 16 The Brazilian Army reached the border of Rio Grande do Sul and soon surrounded Uruguaiana . The troops received reinforcements and sent at least three orders to surrender of colonel Estigarribia . In September 11 Dom Pedro II arrived at the scene of the siege , where there were the presidents of Argentina Bartolomé Mitre and Uruguayan Venancio Flores And several military leaders , such as Admiral Tamandaré . The allied forces of the siege then counted with 17 , 346 combatants , and 12 , 393 Brazilians , Argentines and 1220 Uruguay 3802 , and 54 cannons . The surrender came in September 16 of Estigarribia when he entered into agreement with the conditions . Ended with this episode the first phase of the war in that Solano López had launched its major offensive operations in the invasion of Argentina and Brazil . In early October , the Paraguayan troops of occupation in Corrientes Lopez received the order to return to their bases in Humaitá . At that time , Allied troops were gathering themselves under the command of Mitre in the camp Concord In the Argentine province of Entre Ríos . With the Field - Marshal Manuel Luís Osório ahead of the Brazilian troops . Part of these went to Uruguaiana , which was to strengthen the siege of this city by the Brazilian army in Rio Grande do Sul , commanded by Lieutenant General Manuel Marques de Sousa , baron and then Conde de Porto Alegre . The Paraguayans yielded on September 18 of 1865 . In the following months , the Allied troops , with Mitre as commander in chief , freed the last redoubts Paraguayans in Argentina , the cities of Corrientes and San Cosme At the confluence of the rivers Paraná and Paraguay In late 1865 . At the end of the year 1865 , The offensive was the Triple Alliance . Their armies numbered more than 50 000 men and prepared to invade Paraguay . The Invasion Of Paraguay . Strengthened , with an effective fifty thousand men , the allies threw themselves on the offensive . The invasion of Paraguay began ascending the course of Paraguay River From the Step Homeland . Under the command of Gen . Manuel Luís Osório , and with the assistance of the imperial fleet , transposing Parana River In April 16 of 1866 , And heading into enemy territory conquered in Step Homeland A week later . April 1866 to July 1868 Military operations were concentrated at the confluence of the rivers Paraguay and Paraná Where were the main fortifications of the Paraguayans . For more than two years the progress of the invaders was blocked , despite initial Triple Alliance victories . The first position taken was the Fortress Itapiru . After battle of the Fatherland Step and the Estero Bellaco ( May 2 ) , The allied forces camped on swamps of Tuiuti In May 20 , Where he suffered an attack of Paraguay four days after . The first Battle of Tuiuti , The largest pitched battle in the history of South America and one of the most crucial and bloodiest conflict , was won by the Allies in May 24 of 1866 and left a toll of 10 , 000 dead . For health reasons in July 1866 Osório passed the command of the 1st Corps of the Brazilian army to General Polidoro da Fonseca Quintanilha Jordan . At the same time , arrived at the theater of operations the 2nd Corps , brought from Rio Grande do Sul by the Baron de Porto Alegre ( 10 , 000 men ) . The path to Humaitá was not clear . Commander Mitre took the reservations of ten thousand men brought by the baron of Porto Alegre and decided to attack the batteries Fort Curuzú and Fort Curupaiti Who manned the right position Humaitá on the banks of the Paraguay River . The battery Curuzu was won in September 3 by the baron of Porto Alegre . Was not obtained , however , the same success in Curupaiti , Which resisted the attack of 20 000 Argentines and Brazilians , led by Mitre and Porto Alegre , with support from the squadron admiral Tamandaré . In September 22 The allies were decimated by the enemy , five thousand men died within hours . This failure has created a crisis of command and stopped the advance of the Allies . In this phase of the war , stood out many Brazilian military . Among them , the heroes of Tuyutí : General José Luis Mena Barreto , Brigadier Antônio de Sampaio , Patron of the gun infantry of Brazilian Army , Lieutenant - Colonel Emílio Luís Mallet , Patron of artillery and Osorio and himself , patron of cavalry In addition to Lieutenant Colonel Joao Carlos de Vilagrã Cabrita , Patron of the gun engineering , Killed in Itapiru . Third phase : Stalemate . In the second period of war ( 1866 - 1869 ) , the friction between Osorio ( commander of the Brazilian forces ) and the Argentine president , who opposed the persecution of Paraguay , led the Brazilian government to replace their commander . On October 10 of 1866 the command of the Brazilian forces was given to Marshal Luís Alves de Lima e Silva , Marquis and later Duke of Caxias , who arrived in Paraguay in November , finding the Brazilian army practically paralyzed . The contingents of Argentines and Uruguayans were being gradually withdrawn from the allied army , plagued by epidemics . Disagreements between Venancio Flores ( Uruguay ) and Mitre ( Argentina ) and internal problems forced the withdrawel of both of them from the field and their return to their countries , leaving Brazil practically alone . Tamandaré was replaced in command by Admiral Joaquim José Inácio , future Viscount of Inhaúma . While this was happening , Osorio organized the 3rd Corps in Rio Grande do Sul ( five thousand men ) . In Mitre ' s absence , Caxias assumed the general command and the restructuring of the army . Between November 1866 and July 1867 , Caxias organized a medical corps ( to give assistance to numerous wounded and combat the epidemic of cholera ) and a system for supplying the troops . He also succeeded in procuring the collaboration of the imperial fleet , which resented the command Mitre , in the campaign against Humaitá . During this period military operations were limited to skirmishes with the Paraguayans and bombardments against the batteries at Curupaiti . Lopez took advantage of the disorganization of the enemy to reinforce his stronghold at Humaitá . Despite the efforts of Caxias , the allies did not resume the offensive until July 22 of 1867 . The march to outflank the left wing of the Paraguayan fortifications was the basis of Caxias ' s tactics to overcome the Paraguayan strongholds , cut the links between Asuncion and Humaitá and subject the fortress to a siege . To this end , Caxias directed a march toward Tjuyu - Cue . On August 1 Mitre returned to command and insisted on attacking by the right wing , which has been disastrous at Curupaiti . Although Caxias ' maneuver had been successful , the delays allowed López to extensively fortify this region and create the so - called " Quadrilateral . " Fourth phase : the Allies returned the offensive ( 1868 - 1869 ) . Taking Humaitá . Mitre gave orders that the imperial fleet forced the passage in Curupaiti and Humaita . In August 15 Two divisions of five battleships exceeded , lossless Curupaiti , but were forced to hold up against the powerful guns of the fortress of Humaita . That has prompted new disagreements in the High Command . Mitre wanted the squadron to proceed . The Brazilians , however , considered unwise and useless to proceed , while ground attacks are not concatenated to involve the Quadrilateral , which started finally in August . From Thuya - Cue the allies headed north and took San Solano , Pilar Village and Tayi On the shores of Paraguay River , which completed the encirclement of the fortress by land and cut off communications between river and Humaitá Assumption . In November 3 of 1867 , in reaction , Lopez struck the rear of the Allied position Tuiuti . In that Second Battle of Tuiuti Lopez came close to victory , but by strengthening brought by General Porto Alegre , the Brazilians won . In January 1868 With the removal of Mitre , who returned to Argentina , Caxias returned to assume the overall command of the Allies . In February 19 the imperial fleet , captain - of - water - and - war Delfim Carlos de Carvalho After Baron ' s Passage Forced the passage Humaitá . Although the vessels battleships they had passed the fort , arriving to bombard Asunción , only July 25 of 1868 Humaita , totally surrounded , fell after a long siege . December . Solano López Humaitá left , with part of his troops in March , going to settle in San Fernando . There found that some officials of his government and his brother Benign plotting to overthrow him . Formed a council of war to prosecute those involved , hundreds were executed in what became known as the massacre of San Fernando . Made the occupation of Humaita , Allied forces led by Caxias marched 200 km until Palmas , Bordering the new enemy fortifications ( September 30 ) . Situated along the stream Piquissiri these fortifications barred the way to Asuncion , supported by the Fortifications of Lomas Valentinas . There López had concentrated 18 , 000 Paraguayans in a fortified line that exploited the terrain and supported the strong Angostura and Ita - Ibaté . Resigned to frontal combat , the Brazilian commander envisioned , then the most brilliant and daring operation of the conflict : maneuver Piquissiri . In 23 days did build a road 11 km through the Chaco swamp that stretched along the right bank of Paraguay River , While Brazilian and Argentine forces was in charge of entertainment front line of the Piquissiri . It then performed the maneuver , three bodies of the Brazilian Army , with 23 , 000 men , were transported by the imperial fleet of Humaita to the right bank of the river , traveled to the Chaco road toward the northeast , reembarked opposite the port of Villeta , and went ashore at the port of San Antonio and Ipané Again on the left bank , twenty kilometers to the rear lines of the fortified Paraguayan Piquissiri . Lopez was completely surprised by this move , such was their confidence in the impossibility of large numbers crossing the Chaco . In night of December 5 , Brazilian troops were ashore , and instead of moving to the capital , already evacuated and bombarded by the fleet , began next day movement to the south , known as the " December to dismember " . and December consisted of a series of victories achieved by in Caxias December 1868 . On the same day , General Bernardino Caballero tried to stop them crossing the bridge over the creek Itororó . In making the bridge of Itororó , Caxias , 65 years old , broke into a gallop toward the enemy , with sword in hand , exclaiming : " " follow me those are Brazilians ! " " was not killed by luck . Having concluded Battle of Itororó The Brazilian Army continued to march and annihilated in the town of Avai In December 11 The two divisions Caballero . In December 21 And received the necessary supply for Villeta , Brazilians attacked Piquissiri the rear and , after six days of continuous fighting , won the position of Lomas Valentinas With that forced him to trim Angostura to surrender in December 30 . The battles of December exhibited mortalities stunning on both sides , as well as attempts to retreat from the Brazilian troops , hampered by the presence of Caxias in forefront . Lopez , accompanied only by some contingent fled north toward the mountains . The commander in chief has traveled to Asunción , evacuated by the Paraguayan and taked in January 1 of 1869 by Imperial troops led by Colonel Hermes Ernesto da Fonseca ( later Marshal and first resident of Brazil ) , father of the future Marshal Hermes da Fonseca . On 5 , Caxias entered the city with the rest of the army and 13 days after For reasons of health , left his command and returned to Brazil . The departure of Caxias and his top military chiefs did growing despondency among the troops , with the proliferation of requests for waiver of the officers and volunteers . Fifth phase : hunting Solano López ( 1869 - 1870 ) . End of war : the command of Count d ' Eu . In the third period of war ( 1869 - 1870 ) , The brazilia emperor ' s son - in law , Louis Philippe Gaston , Conde d ' Eu , Was appointed to lead the final phase of military operations in Paraguay , as is sought in addition to the total defeat of Paraguay , the strengthening of the Brazilian Empire . Husband ' s of Princess Isabel was one of the few members of the imperial family with military experience , since in 1850s participated as a junior officer , of a campaign Spanish in War in Morocco the appointment of a member of the imperial family planned to cut the operational difficulties of the Brazilian forces , problem exacerbated by many years of campaigning by the dissatisfaction of the veterans and the conflicts , political and personal , they spread among the more experienced officers . In August 1869 , the Triple Alliance installed a provisional government in Asunción puppet ally opposed to Solano , headed by Paraguayan Cirilo Antonio Rivarola . The Empire has accelerated the process for forming a government promise to hold democratic elections next year and create a constituent assembly . Solano López , building endurance , redid a small army of 12 , 000 men and 36 guns in the mountainous region of Ascurra - Caacupé - Peribebuí , village which became his capital . In front of 21 000 men , Count d ' Eu led the campaign against the Paraguayan resistance , the call Campaign of the Cordillera , which lasted over a year , unfolding in several outbreaks . Especially in Brazil , after the Conservatives had returned to power in the Imperial Chamber , became a priority the reconstruction of state of Paraguay . For this to be recognized , was needed victory over Solano . The process was accelerated by the entry into the Argentine government in 1868 by Domingo Faustino Sarmiento , whose expansionist desires the Empire of Brazil feared . The Brazilian Army flanked the enemy positions from Ascurra and won the battle of Peribebuí ( August 12 ) , where Lopez had transferred his capital . After the battle of Peribuí , Count d ' Eu seems to have been exasperated by the obstinacy Paraguay to continue the fight , doing nothing to prevent the beheading of prisoners captured during and after the fighting . In the next battle , Campo Grande or Nhu - Guaçu ( August 16 ) , the Brazilian forces were faced with an army made up mostly by teenagers and children and the elderly , the force recruited by the Paraguayan dictator . The defeat ended the cycle of Paraguayan War battles . The next steps consisted of mere hunt for Lopez , who left Ascurra and followed for less than three hundred men , plunged into the woods , always marching to the north . Two detachments were sent in pursuit of Paraguayan president , who in the forests in the north accompanied by 200 men . On 1 March 1870 , troops of General José Antônio Correia da Câmara ( 1824 - 1893 ) , Viscount of Pelotas , surprised the latter camp Paraguay , Cerro Cora , where Solano López was wounded by the spear out Chico Devil and then shot in the banks of the river Aquidabanigui , after refusing to surrender . After Cerro Cora , Brazilian troops were euphoric , murdered civilians , setting fire to camps and killing the wounded and sick that were in ranching . That was not the wish of Emperor Dom Pedro II , who preferred to have the prisoner killed Lopez . In Rio de Janeiro , the death of Lopez was very well received and the emperor regained his popularity had been shaken by the costly war . On June 20 , 1870 , Brazil and Paraguay signed a preliminary agreement for peace . Consequences . Mortality . Paraguay suffered a great reduction in its population . The war has emphasized an imbalance between the amount of men . Some sources say that 90 % of Paraguay ' s population would have perished at the end of the war . contemporary estimates , however , determine the percentage of loss of life between 15 % and 20 % of the population . Of the approximately 160 , 000 Brazilians that fought in the War of Paraguay , best estimates indicate about 50 000 deaths and another thousand invalid . Still others estimate that the total number of combatants may have reached 400 , 000 , with 60 , 000 killed in battle or by disease . Uruguayan forces counted on nearly 5600 men , of which slightly more than 3 , 100 died during the war due to battle or by disease . Argentina has already lost about 18 000 combatants from among the nearly 30 , 000 involved . Other 12 000 civilians have died mainly due to diseases . Fact is that the Paraguayan War was not different from other conflicts that occurred during the nineteenth century . The high mortality rates were due not only on account of armed encounters . Diseases resulting from poor nutrition and poor hygiene conditions appear to have been the cause of most deaths . Among Brazilians , at least half of the deaths were caused diseases typical of situations of war in the nineteenth century . The main disease during the war seems to have been cholera . Post War . There was a treaty of peace together . Although the war ended in March 1870 The peace agreements were not completed immediately . The negotiations were hindered by the refusal to acknowledge the Argentinian Paraguayan independence . Brazil did not accept the claims of Argentina on a large part of Gran Chaco , A region rich in Paraguay quebracho ( Product used in the industrialization of leather ) . The boundary question between Paraguay and Argentina was resolved through long negotiations between the parties . The only region upon which never reached a consensus - the area between the Green River and the main branch of Pilcomayo River - Was arbitrated by President state - Street Band Rutherford Birchard Hayes stated that the Paraguayan . Brazil signed a separate peace treaty with Paraguay , in January 9 of 1872 , Obtaining freedom of navigation on the Paraguay River . Was confirmed the boundaries claimed by Brazil before the war . The treaty also stipulated a war debt that was intentionally undersized by the imperial government of Brazil but was actually forgiven in 1943 by Getúlio Vargas In response to a similar initiative in Argentina . The recognition of the independence of Paraguay by Argentina was only done in Buenos Aires Conference In 1876 When peace was finally established . In December 1975 When presidents Ernesto Geisel and Alfredo Stroessner Asuncion signed a Treaty of Amity and Cooperation , the Brazilian government returned to Paraguay their trophies the war . Conclusions . The Paraguayan war - torn villages were abandoned and farmers survivors migrated to the outskirts of Asuncion , dedicating themselves to subsistence agriculture in the central region of the country . The Other lands were sold to foreigners , mainly Argentines , and transformed into estates . The industry went into decline . The Paraguayan market opened to British goods and the country was forced to issue its first loan abroad : a million pounds of England Which could be considered the most power , have benefited from this war , because in addition to seeing the competition extinct in Paraguay South America as an example of development , Brazil and Argentina saw increasing foreign debts . After the war , much of Paraguay ' s best land was annexed by the victors . Brazil had the region between the rivers Apa and White , Increasing for the southern state of Mato Grosso . Argentina annexed the territory of the Missions and the area known as Chaco Central ( Argentine territory of Formosa ) . Throughout the long campaign , the provinces of Entre Rios and Corrientes fueled Brazilian troops with cattle , foodstuffs and other products . Brazil , which supported the war almost alone , paid a high price for victory . During the five years of fighting , the expenses of the Empire came to double its revenue , causing a financial crisis . The slavery began to be questioned , because the slaves who fought for Brazil remained slaves . The Brazilian Army has become a significant new force in national life . Had become a strong institution that , with the war , gained tradition and internal cohesion and represent a significant role in further development of the country ' s history . Furthermore , there was the formation of a disturbing corporate spirit in the army .