The Cisplatine War was an armed conflict fought in the 1820s between the Empire of Brazil and the United Provinces of the Río de la Plata over control of the Banda Oriental following its annexation by Brazil as the Cisplatina province. It was fought in the aftermath of the United Provinces' and Brazil's independence from Spain and Portugal, respectively, and resulted in the independence of Cisplatina as the Oriental State of Uruguay.
In 1816, the United Kingdom of Portugal, Brazil and the Algarves carried out an invasion of the Banda Oriental and, after defeating the local resistance led by José Gervasio Artigas, annexed it under the name of Cisplatina. After Brazil's independence in 1822, Cisplatina remained as part of Brazil. Wishing to gain control of the region, the United Provinces sent a diplomatic mission to Brazil in 1823 to negotiate a peaceful Brazilian withdrawal, but it failed. In 1825, a group of patriots known as the Thirty-Three Orientals, supported by the Argentine government and led by Juan Antonio Lavalleja, launched a rebellion against Brazil. On 25 August of that year, in the Congress of Florida, they declared Cisplatina's independence from Brazil and its unification with the United Provinces. After a series of initial skirmishes, they defeated the Brazilians at the battles of Rincón and Sarandí, prompting the Argentine Congress to proclaim Cisplatina reintegrated into the United Provinces on 25 October. In response, Brazil declared war on the United Provinces on 10 December 1825 and imposed a naval blockade on the River Plate.
The United Provinces managed to occupy the Uruguayan countryside with the help of the local insurgents, however, its forces never managed to capture Montevideo and Colonia del Sacramento or penetrate deeply into Brazilian territory. Likewise, the Brazilians did not manage to regain control of the countryside or achieve a decisive victory in order to repel the Argentines, with both armies clashing at the battle of Ituzaingó, the largest battle of the conflict. Thus, the war on land reached an impasse. At sea, however, the Brazilian Navy obtained better results, despite the Argentine resistance, whose small fleet, led by Irish-born admiral William Brown, was mostly destroyed.
The economic burden and internal political disputes caused by the war in both states, especially the naval blockade and the stalemate on land, led both countries to start peace negotiations. In 1827, the Argentine minister plenipotentiary Manuel José García, exceeding his instructions, signed a peace treaty with Brazilian representatives, renouncing Argentine claims over Cisplatina and agreeing to compensate Brazil for privateering losses. The treaty was rejected by Argentine president Bernardino Rivadavia, but its terms generated enormous backlash, contributing to the president's resignation. The national presidency was dissolved and Manuel Dorrego was elected governor of Buenos Aires. Dorrego continued the war while assuming responsibility for the conduct of the United Provinces' foreign affairs. The conflict continued until 27 August 1828, when Argentine and Brazilian representatives, under British mediation, signed the Preliminary Peace Convention, by which Cisplatina would become an independent state and hostilities would cease.
After the war, tensions in Argentina between the Federalists and the Unitarians increased. A Federalist, Manuel Dorrego was deposed and executed by the Unitarian general Juan Lavalle, reigniting the conflict between the two factions. In Brazil, the war's financial cost, aggravated by the damage done to Brazilian trade by Argentine privateers, and the loss of Cisplatina, added to the internal political disputes surrounding emperor Pedro I, which ultimately led him to abdicate the throne in favour of his 5-year-old son Pedro II in 1831, ushering the regency period.
Background
Colonial disputes
Following the South American wars of independence, the region known as the Banda Oriental became a point of contention between the Empire of Brazil and the United Provinces after Brazil's independence in 1822. This dispute was inherited from the Portuguese and Spanish colonial empires, whose borders in the River Plate basin had never been settled. It began in 1679, when the Portuguese crown, which had always considered the River Plate as Brazil's natural southern border, ordered Manuel Lobo, the governor of the Captaincy of Rio de Janeiro, to found the fortress town of Colônia do Sacramento, in an easily defensible peninsula with a natural harbour, on the right bank of the river, right in front of Buenos Aires, which he effectively did in 1680. By expanding into the River Plate basin, the Portuguese wanted to secure access to the continent's interior and also divert the smuggling of silver from Upper Peru away from Buenos Aires.
The Spaniards, wishing to solidify their control over the region, also founded a colony on the opposite bank of the river in 1724, when Bruno Mauricio de Zabala founded the town of Montevideo. Finally, Spain created the Viceroyalty of the Río de la Plata in 1776, with its capital in Buenos Aires. After centuries of wars and settling attempts between the two empires, Colônia do Sacramento finally became a Spanish possession by the 1801 Treaty of Badajoz.
With the outbreak of the 1810 May Revolution in Buenos Aires and the Argentine struggle for independence that ensued, Montevideo, under the command of viceroy Francisco Javier de Elío, remained loyal to Spain. The Primera Junta of Buenos Aires then set out to subdue Montevideo and Elío, who, finding himself without support from Europe, requested assistance from Carlota Joaquina, the Spanish wife of Portuguese prince regent John of Braganza. The Portuguese crown, which had fled to Brazil in 1808 after the French invasion of Portugal, then took the opportunity to invade the Banda Oriental in 1811. An army named "Peacekeeping Army of the Banda Oriental" was assembled and command was given to Diogo de Sousa, who had orders to help Elío. Diogo de Sousa then led the troops into the Banda Oriental, but a few months later, on 20 October 1811, Elío signed the Treaty of Pacification with the First Triumvirate, which had succeeded the Primera Junta, and so the Argentines, led by José Rondeau, lifted the siege on Montevideo and left the Banda Oriental. Likewise, the Portuguese signed an armistice with Buenos Aires on 26 May 1812 and also left the region.
In this struggle for control over the region, José Gervasio Artigas, a native of the Banda Oriental who had defeated the Spanish at the battle of Las Piedras in 1811, opposed the treaty; Artigas left the Banda Oriental with 16 thousand people, in what became known as the Oriental Exodus, and continued to fight against Spanish rule. In 1814, Artigas, who had fought for independence alongside Buenos Aires troops since 1810, finally defeated the last Spanish forces in the region. Despite receiving military assistance from Buenos Aires in the independence war, Artigas opposed the Buenos Aires elites' intention of centralizing power and resisted their attempts to take control of the Banda Oriental, defeating Manuel Dorrego at the battle of Guayabos in 1815 and forming the League of the Free Peoples. This league was based on federalism and social reform, which gained him the support of the poor peoples of the countryside; thus, Artigas became an obstacle to Buenos Aires' political ambitions.
Artigas also opposed Portuguese intentions of asserting control over the region, and attacked the neighboring Brazilian province of Rio Grande do Sul near Quaraí. His influence was also felt in the north, inhabited by Brazilians. In the account of John Parish Robertson, the Banda Oriental fell into "the most unbridled disorder and horrible anarchy" and Artigas' name became "synonymous with bandit, murderer and thief"; this was the pretext now king John VI needed to once again invade the region in 1816. The new invasion, led by Carlos Frederico Lecor, was instigated and unopposed by Buenos Aires, who feared Artigas. The invading Luso-Brazilian forces repeatedly defeated Artigas and his men, with Lecor conquering Montevideo on 20 January 1817. Artigas still unsuccessfully tried to resist, being finally defeated at the battle of Tacuarembó in 1820; with no hopes of continuing the resistance, he went into exile in Paraguay, where he spent the rest of his life as a prisoner of Paraguayan dictator José Gaspar Rodríguez de Francia.
Brazilian rule and failure of negotiations
On 10 April 1821, under orders of King John VI, Lecor convened a congress of elected representatives from all of the Banda Oriental that would deliberate on their fate. A few months later, on 31 July 1821, the Montevideo cabildo approved its incorporation into the United Kingdom of Portugal, Brazil and the Algarves as a province under the name of Cisplatina. According to Carlos Oberacker, the decision reflected the local population's exhaustion and desire for peace "after years of bloody civil war and anarchy, as well as the perpetual state of revolution in which Spanish America—and the Río de la Plata region in particular—found itself," whereas union with the monarchy offered "tranquility and economic prosperity hitherto unknown to them". Accession to the United Kingdom would take place under the indispensable condition that "the bases presented be respected, fulfilled, observed, and enforced"—notably the desire to make Cisplatina a federated state of the kingdom. Upon assuming the provincial government, Lecor gained the support of a local elite group known as the "Baron's Club". According to Pablo Ferreira, for them the new leadership represented a "guarantee of economic recovery, respect for property rights, and the gradual modernization of institutions". They benefited from the new land policy, public offices, and marriage alliances between Luso-Brazilian officers and women from the local elite.
The following year, when prince Pedro of Branganza openly rebelled against the Portuguese Cortes, the Brazilian government juntas in the provinces gradually joined the independence cause, with the exception of Cisplatina, whose junta, led by Portuguese-born Álvaro da Costa, voted to remain loyal to Portugal. Brazilian patriots, loyal to prince Pedro and under the command of Carlos Frederico Lecor, then besieged and blockaded the Portuguese troops garrisoned in Montevideo, finally defeating them in 1824. The local population was divided on the matter; many notable natives of the province, such as Fructuoso Rivera and Juan Antonio Lavalleja, joined Lecor against the Portuguese, while others, such as Manuel Oribe, sided with Portugal; the towns and villages of the countryside, such as Colônia do Sacramento, San José, Cerro Largo and Maldonado, had also joined the Brazilian cause. Thus, once the Portuguese were defeated and left to Lisbon, Cisplatina remained as part of the Empire of Brazil.
Following the United Province's recognition of Brazil's independence on 25 June 1823, the country immediately began diplomatic talks with the Empire regarding Cisplatina, which the Argentine government considered theirs and wanted to gain possession of. In 1823, the Argentines sent José Valentín Gómez to the Brazilian court in Rio de Janeiro in order to negotiate a peaceful Brazilian withdrawal from the region. The Argentine diplomatic mission made a series of proposals and, after receiving no response from the Brazilian government, demanded a reply in February 1824. The answer was given on 6 February 1824, in which the Imperial government promptly rejected any negotiations regarding the cession of Cisplatina.
Emperor Pedro I of Brazil, who had been informed of the situation in Cisplatina by Lecor, believed the natives of the province wanted to remain as part of the Empire; however, Lecor had surrounded himself with people who were sympathetic to Brazil, which prevented him from knowing the true intentions of the province's inhabitants. Likewise, after the Brazilian patriots defeated the Portuguese and entered Montevideo, the locals swore the Brazilian Constitution on 10 May 1824, by which Cisplatina would become part of Brazil, "subject only to the terms of the Province's incorporation". This situation gave off the impression the inhabitants of the province wanted to be part of the Empire. In reality, however, this was not the case: apart from Montevideo and other small cities along the coast, all the countryside, where Artigas' influence was still strong, wished for independence, with the locals disguising their intentions.
According to Pedro Calmon, the province had sent two deputies to the 1823 Constituent Assembly that was tasked with drafting Brazil's first constitution. The constitution drafted by the Assembly was rejected by emperor Pedro I, who dissolved it and issued a constitution himself in 1824. The draft provided for treating Cisplatina as a federated entity of the Empire. In any case, Oberacker Jr. emphasized that the Empire of Brazil did not treat Cisplatina as a sui generis state, ultimately treating it like any other province of the empire while retaining its military government—unlike the other Brazilian provinces, which "were already administered by civilian authorities", further souring their relations.
The Oriental rebellion
Landing of the Thirty-Three Orientals
When news of the Argentine diplomatic mission's failure reached Montevideo, the locals, including various of the notable leaders who had previously fought alongside the Brazilians against the Portuguese, started to conspire against Brazilian rule, wishing to unite with the United Provinces and forming a secret society named Caballeros Orientales. The conspiracy was discovered by Lecor and some of the more prominent conspirators had to flee to Buenos Aires. Among the conspirators, who numbered more than two hundred people, was Fructuoso Rivera, who was a colonel in the Brazilian Army. Despite having distinguished himself in the service of the Empire and having received several promises of career advancement, Rivera decided to revolt, but continued to disguise his intentions from the Brazilian Court.
On 19 April 1825, a group of 33 men known as the Treinta y Tres, or the Thirty-Three, led by Juan Antonio Lavalleja, left Buenos Aires, crossed the Uruguay River and landed on Agraciada beach with arms and ammunition, starting the rebel movement against the Empire of Brazil; the action had Rivera's knowledge and collusion. After landing, Lavalleja and his men set out in search of recruits. The next day, the patriots, already numbering more than 200 men, marched to Soriano and defeated the small garrison there, which was commanded by Julián Laguna, who joined them. People from every corner of the province began to take up arms and present themselves to the patriots. According to John Armitage, a foreign observer present at the time, the insurgents were few in number, but superior to their opponents when on horseback, also having "a perfect knowledge of the face of the country".
Rivera's defection and first actions
When news of Soriano's fall reached Lecor, he ordered Rivera to attack it. After leaving Colonia del Sacramento to confront the rebels, Rivera was imprisoned by them without resisting, defecting to their side on 27 April. On 1 May, Rivera, whose defection was still unknown to the Brazilian Army, went from Monzon to San José, where he met Brazilian colonel Vicente Rodrigues Borba, who, having arrived there with troops from Curitiba and São Paulo, was to join forces with Rivera. Unaware of Rivera's defection, Borba went to meet him, at which point he and his entire column of 300 men were captured by Lavalleja.