According to Education VV, López’s campaign plan was to attack the three allies, that is to say, in the north, with the troops commanded by generals Barrios and Rasquín and in the south with the forces placed under the orders of generals Robles, Duarte, Estigarribia. On April 15, 1865, Robles, at the head of three thousand soldiers, landed in Corrientes. While Robles invaded the province of Corrientes, Estigarribia and Duarte, with an army of twelve thousand men, crossing the Argentine Missions, operated along the Río Uruguay, with the aim of invading the province of Río Grande. These troops operated in isolation from the Robles group; and this isolation was the main cause of their defeat. On August 16, 1865, Estigarribia entered the Uruguayan republic, while Duarte camped in a place called Yatay, on the opposite bank of the river. On August 17, Duarte’s contingent was destroyed by the Uruguayan army. Estigarribia, attacked by forces far superior to his own, was forced to surrender to the Argentine general Miter.
The news of this failure led López to order the Paraguayan forces to evacuate the Corrientes; abandoned this locality, they went to the “Paso de la Patria” around which the general concentration of the republican troops took place, under the direct command of Lopez. The Paraguayan forces, on May 2, 1866, attacked the allies who had managed to penetrate Paraguayan territory. Another battle took place on May 24, with a very disadvantageous outcome for the López army, which was almost destroyed. In spite of this, the allies did not know how to draw out from the victory and, continuing to remain firm in the positions already occupied before, allowed the Paraguayan forces to reorganize, to rearrange themselves, and finally to fortify themselves in Curupaytí. In this locality another great military event took place on 12 September 1866 in which the Paraguayans, reorganized, were able to defeat and flee the allied army. From that day no other important facts were noted until November 3, when the López troops, attacked the allied camp of Tuyutí by surprise, managed to carry out a large loot of weapons, cannons, provisions. Meanwhile, another misfortune was added to the atrocities of the war: cholera which, which broke out in May 1867, claimed thousands of lives in the entire region. In the following two years of war, the situation of Lopez gradually worsened: and after the battle of Ita-Ybaté, in which handfuls of Paraguayans were seen resisting allied battalions and regiments, the López withdrew, followed by a few men, at Cerro Leon. Before leaving what had been the Paraguayan army, López bled his hands with blood by having his brother Benigno, Bishop Palacios de Berges and Colonel Alén shot, on charges of conspiring against him. With this same pretext of conspiracy against him, Lopez had more than a thousand people belonging to the most varied civil classes shot during the war. This excess of cruelty, by turning the public opinion of the country against Lopez, and giving his adversaries ever new weapons against him, did much to precipitate military operations. Masters of the field, the allies marched on Asuncion, which was occupied by the Brazilians.
With López dead, peace signed (June 20, 1870), great was the number of proscribed Paraguayans who returned to their homeland: the dispersed population began to flow into Asunción where, on July 22, those voters who could be found and rushed to the polls, appointed a triumvirate, which was accepted by the people on August 15, 1870, on the occasion of the anniversary of the founding of the city. On November 24-25 a new constitution of the republic was approved. Cirillo Antonio Rivarola was then provisional president of the republic, who was re-elected on 25 November, according to the new constitution. In the following years the most notable facts were the agreement with Brazil of January 9, 1872, by which Paraguay ceded the eastern part of the Rio Apa to the north and the treaty of February 3, 1876, with the Argentine Republic, which left the decision on territorial matters to the award of the president of the United States; the award fixed the border with the Argentine Republic south of the Chaco and west of the Paraguay River, by means of the main branch of the Pilcomayo.
The following years are marked by the contrasts between the two parties, “colorado” (conservative) and radical liberal, contrasts that have repeatedly degenerated into real civil wars, into coups d’etat in which the army actively intervenes.: thus President Juan Gill was killed on April 12, 1877 during a riot; President Juan B. González was overthrown by the liberal revolution, led by General Benigno Ferreira, in December 1904; President Manuel Gondra was forced to resign in January 1911. In this last episode, the internal disturbances were very serious: in 1911 the July revolt took place against Colonel Albino Jara who, having overthrown President Gondra, had become dictator; then, against Jara’s successor, Rojas, there was a second revolution (November 1911-January 1912, with the resumption of troubles in March). However, a certain dividing line in Paraguay’s more recent history is that while the “colorado” party held power from 1874 to 1904, the liberal party prevailed from 1904 onwards.
The question that dominates the Paraguayan political life of the last period and which has entered its acute phase in recent years, from 1928 to today, is the question of the Chaco Boreal, whose possession is disputed to Paraguay by Bolivia. The question, which has already been felt since 1880, when the loss of the Antofagasta region, conquered by Chile, deprived Bolivia of its only outlet to the sea, arose on the following legal bases. The Bolivian thesis is this: throughout the colonial period the Chaco Boreal had belonged to the audiencia of Charcas (Bolivia), whose territories passed to the republic of Bolivia, according to the principle proclaimed by Simone Bolívar in 1810, of the uti possidetis to regulate the borders of the nascent states. Paraguay counters, on the basis of a distinction between the uti possidetis de iure and the uti possidetis de facto, that effective dominion in Chaco has always been exercised by the governors of Paraguay, in the administrative field, by the bishops of Asunción, in the religious field; that the colonization of the Chaco was always and exclusively carried out by Paraguayans.
The question, of vital importance, because Bolivia only with the possession of the Chaco Boreal could have, with the outlet into the Paraguay river, an outlet, albeit indirect, on the sea, had already given rise in the last twenty years of the century. XIX, to disputes and agreements; in January 1907, following Bolivian military moves, the Soler-Pinilla convention was reached which submitted the question to the arbitration of the President of the Argentine Republic, meanwhile establishing the status quo for the territory between 61 ° 30 ‘and 62 ° longitude. Due to various circumstances, the agreement was not followed: and although not translated into resolutive acts, a new agreement of April 5, 1913 remained, which confirmed the status quo provisional, until arbitration decision or final agreement. New negotiations started in 1927 between the two governments remained fruitless; and instead in December 1928 the first armed conflicts broke out between the Bolivian and Paraguayan troops in the Chaco. The intervention of the Pan-American Congress, then of the League of Nations seemed to lead to a peaceful solution to the conflict: on January 3, 1929 the two governments signed a protocol which established the appointment of a commission of inquiry; on 19 September the delegates of the two countries to the League of Nations announced that the two governments had accepted the proposals of the commission, which established the resumption of diplomatic relations between Bolivia and Paraguay and the return to the status quo territorial of December 5, 1928. But soon the conflict was rekindled: already at the beginning of 1930, but especially from the summer of 1932, the war was rekindled in the Chaco, where it still continues (November 1934), with various alternatives. Paraguay withdrew from the League of Nations in February 1935.