The Treaty of the Triple Alliance allied the Empire of Brazil, Argentina, and Uruguay against Paraguay. Signed in 1865, after the outbreak of the Paraguayan War, its articles (plus a Protocol) prescribed the allies' actions both during and after the war. An English translation of the text is reproduced in this article.
The war lasted until 1870 and led to the near-annihilation of Paraguay. After Paraguay's defeat, Brazil and Argentina, who were traditional enemies, hovered on the brink of mutual warfare for six years because of disputes and misunderstandings about the treaty.
According to article XVI Argentina was to receive a 600 km strip of territory in the Chaco north of the Pilcomayo River, nearly up to the Bolivian border. From the start the Brazilian government set out to frustrate the implementation of this particular stipulation, and eventually succeeded. Today this territory — the Central Chaco — belongs to Paraguay.
Background
Although the Empire of Brazil and Argentina were traditional enemies, they, together with Uruguay, united against Paraguay in 1865. The Paraguayan War has been described by Leslie Bethell as "the bloodiest inter-state war anywhere in the world between the end of the Napoleonic Wars in 1815 and the outbreak of the First World War in 1914".
Its causes were various, and have been hotly disputed by modern writers; they have even been traced back to territorial disputes between Portugal and Spain stemming from the Treaty of Tordesillas (1494). "Indeed the Paraguayan War was just the last chapter in a two-century conflict between the Spanish and Portuguese over the region". But for the purposes of this article, it may be enough to outline the geopolitical situation and the immediate antecedents of the treaty.
Disputes over vital communications arteries
In the middle of the 19th century, vast tracts of South America were undeveloped, railways were few and short, and surfaced roads practically did not exist. So navigable rivers were "vital arteries". Of particular relevance were the Paraná and Paraguay rivers. Using the Paraná-Paraguay system, quite large ships could steam 1,870 miles (3,010 km) upriver from Buenos Aires well into the Brazilian Mato Grosso province. These rivers were of crucial importance to landlocked Paraguay, to Brazil and to the trade of some Argentine provinces. It was, as wrote D.S. Chandler
a region which needed only peaceful intercourse and open rivers for rapid economic growth to transform the lives of its inhabitants. Unfortunately, after the onset of the independence era those conditions seldom offered themselves for more than a few years at a time. Wars and political and economic rivalries meant that more often than not, high tariffs and blockades vexed the river system.
Thus Buenos Aires Province under Juan Manuel de Rosas had restricted river traffic to put pressure on upstream Paraguay, and Paraguay under Carlos Antonio López had done the same to put pressure on Brazil. In 1855 a Brazilian naval flotilla threatened Paraguay unless it conceded free navigation of the Upper Paraguay river.
In 1855 Paraguay, with an understandable fear and distrust of its neighbours, began to develop the formidable Fortress of Humaitá. Established near the mouth of the River Paraguay and known as the Gibraltar of South America, the fortress was the gateway to the country. However, it may have caused the Paraguayan government to feel itself invulnerable (wrongly, as it turned out), and it caused tension with Brazil. As explained by lieutenant colonel George Thompson of the Paraguayan Army:
Paraguay made all vessels anchor and ask permission before they could pass up the river. As this was the only practicable road which Brazil had to her province of Matto-Grosso [sic], she naturally disapproved of her stoppage of the river, and gradually accumulated large military stores in Matto-Grosso, with the view, no doubt, of some day destroying Humaitá.
Vessels bound for the Mato Grosso were subjected to bureaucratic harassment, Paraguay's object being to put pressure on Brazil to sign a boundary treaty defining their mutual frontiers. In 1858, however, Brazil explicitly threatened war unless these restrictions were removed, and Paraguay backed down.
Territorial disputes
Furthermore, immense territories were disputed. Not effectively occupied by anyone, except the aboriginal inhabitants, they had no obvious international boundaries. There was a boundary dispute between Brazil and Paraguay going back to colonial times, and there were large areas in dispute between Paraguay and Argentina in the Gran Chaco and in the territory of Misiones. Then, there were no obvious and accepted principles according to which they might have been resolved, and no established practice of international arbitration existed. In international law victory in war was a recognised way of acquiring territory.
Although the Paraguayan War only partly originated in boundary disputes, according to American historian Thomas L. Whigham their existence "always added to the climate of mistrust in the region and made a violent clash on a large scale as likely as anything in history can be".
Paraguayan military buildup
Between 1854 and 1864, and supervised by Francisco Solano López, Carlos Antonio López's son, Paraguay built up its military forces because it thought that the outside world (in particular Brazil, Argentina, the United States, and the British Empire) was disrespecting it. Paraguay imported some 200 foreign technicians, mostly British, and developed an iron foundry, an arsenal, a shipyard, a telegraph and a railway. This modernisation was military-oriented. It also imported from Britain the cadre of a military medical corps who trained Paraguayan medical students. Thus Paraguay became an important regional power. However, as noted by John Hoyt Williams, "the dizzying speed with which his nation was 'modernized' and strengthened tempted López to flex his new muscle and seek an ever-expanding, activist role in international affairs". López became ruler of Paraguay in September 1862 after the death of his father.
Intrigues
A focus of instability was the small Republic of Uruguay, which had achieved independence in 1828. Wrote Professor Whigham:
Two political factions, the Colorado and Blanco Parties, had jostled for power ever since, appealing for support to whatever friends they could find beyond Uruguay’s borders, without ever managing to dominate the government in Montevideo, the Oriental capital, for any length of time. A series of civil wars was the inevitable result.
By the early 1860s, these tensions had come to threaten the broader peace in the
Platine region.
In 1862 the Blanco faction, traditionally hostile to Brazil, and now alarmed because its bitter enemies had seized power in Buenos Aires too,
felt itself to be acutely short of allies. It began a covert diplomatic campaign to turn upriver Paraguay aggressively against Buenos Aires.
This campaign, which continued through 1864, insinuated that Buenos Aires had designs on both Paraguay and Uruguay, who should make a warlike alliance, detach the Argentine provinces of Corrientes and Entre Ríos and seize Martín García Island. Although Francisco Solano López of Paraguay did not trust the Blancos and did not sign an alliance with Uruguay, he nevertheless built up his strength. Because women had always grown the subsistence crops in Paraguay, all able bodied men aged 16–50 were available for service and, in March 1864, they were conscripted for "intensive" military training.
By September 1864 López had an estimated 48,000–150,000 men on a war footing, more than any other power in the region. For Whigham, "Paraguay was the only country in the region that could boast of its military preparedness and a full treasury".
Paraguay invades two Brazilian provinces
However, as events transpired, López did not launch this force on Argentina, but on Brazil. In northern Uruguay lived many who claimed Brazilian nationality, and Brazil complained these people were being mistreated with the connivance of Uruguay's ruling Blanco party: it was a long-standing grievance, and serious atrocities were alleged. In April 1864 political agitation brought Brazilian anger to the boil. In May 1864 Brazil sent a diplomatic mission to Uruguay to demand reparations, accompanied by a naval squadron; Brazilian troops massed along the border. On 30 August 1864 Paraguay warned Brazil against military action in Uruguay, but this was ignored: the Uruguayan War began. In November 1864, Paraguay fired upon and seized the Brazilian government ship Marquês de Olinda as it was steaming up the River Paraguay on its routine monthly voyage to the Mato Grosso. It proved to be carrying military stores. Paraguayan armies proceeded to invade the Brazilian province of Mato Grosso. Later, they invaded Rio Grande do Sul.
Paraguay invades an Argentine province
Paraguay, difficult of access, might have resisted Brazilian retaliation for a long time, but now it took a step that was to give Brazil what it had lacked hitherto: a good forward base from which to attack it. It did so by invading Argentina. First, on 14 January 1865, the Paraguayan government asked Argentina for permission to attack Brazil across the Corrientes Province, which was refused. On 13 April, Paraguayan ships fired upon and seized two Argentine naval vessels moored in the Argentine port of Corrientes and the Paraguayans proceeded to invade the province itself. It prompted the alliance with Brazil.
Upshot
Paraguay had now made war on the much more populous Empire of Brazil, on Argentina (also more populous), and threatened the Colorado faction of Uruguay, which by now had come into power. The three countries had been accustomed to thinking about Paraguay as a backward upstart and were outraged. Their foreign ministers met in Buenos Aires and negotiated the Treaty of the Triple Alliance.
Negotiations
In March 1865, a change of government in Brazil had Liberal Party member Francisco Otaviano de Almeida Rosa sent on a special mission to the River Plate region. Paraguay was at war with Brazil but had not yet attacked Argentina. Some of his instructions were to bolster the Uruguayan government of the pro-Brazilian Venancio Flores, to see how Uruguay might co-operate in the war against Paraguay, and to stop the Argentine government from making any obstacles.
The Paraguayan attack on Argentine territory (13 April) precipitated the Brazil-Argentina alliance so that the 40-year old Otaviano had to negotiate its terms on the spot, without specific instructions from Rio de Janeiro since there was no telegraph link with that capital. His general instructions had been that Paraguay should have to pay for the war, the Humaitá fortifications must be destroyed to guarantee freedom of navigation, and a boundary treaty must be signed with Paraguay according to certain Brazilian proposals of 1853.
Because Argentina and Brazil were traditional enemies, Brazil did not trust Argentine intentions in the River Plate basin. Otaviano thought the Argentine government meant to get aid from Brazil without assuming any obligations so that once the conflict was over, it could reincorporate Paraguayan territory into an Argentine-led successor to the old Viceroyalty of the River Plate. Accordingly, Otaviano insisted that the Treaty of the Triple Alliance guarantee the independence of Paraguay. This did not go down well with Argentina, which insisted on receiving its Misiones and Chaco territorial claims in full, all the way up to the Bolivian border.
The treaty was signed on 1 May 1865.
Brazilian government's reaction
When the Brazilian government discovered what Otaviano had negotiated, particularly his concessions toward Argentina, it was not pleased, and the terms of the treaty were strongly criticised by the Conservative opposition. The general belief in Brazil was that it did not need an alliance with Argentina to beat Paraguay, only that Argentina should keep out of the way. Emperor Pedro II of Brazil referred the Treaty to the Section of Foreign Affairs of the Council of State, which advised that the treaty was disadvantageous to Brazil in several ways by making it too easy for Argentina to annex Paraguay at some future date and too hard for the Brazilian navy to blockade Paraguay if necessary. Otaviano's terms were severely criticised, but he claimed that the situation in 1865 was so critical that if Argentina had wanted to take advantage of it "we would have given them twice, or three times as much."