Banda Oriental in the context of Argentine Civil War

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 Republic 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.

Cisplatina (Brazilian Portuguese: [sisplaˈtʃinɐ], European Portuguese: [siʃplɐˈtinɐ]) was a Brazilian province in existence from 1821 to 1828 created by the Luso-Brazilian invasion of the Banda Oriental. From 1815 until 1822 Brazil was a constituent kingdom of the United Kingdom of Portugal, Brazil and the Algarves. After the independence of Brazil and the formation of the Empire of Brazil the Cisplatina province remained part of it. In 1828, following the Preliminary Peace Convention, the Cisplatina province became independent as Uruguay.

The Argentine Civil Wars (Spanish: Guerras civiles argentinas) were a series of civil conflicts of varying intensity that took place in the territories of Argentina from 1814 to 1853. Beginning concurrently with the Argentine War of Independence (1810–1818), the conflict prevented the formation of a stable governing body until the signing of the Argentine Constitution of 1853, followed by low-frequency skirmishes that ended with the Federalization of Buenos Aires in 1880.

The period saw heavy intervention from the Brazilian Empire, which fought against the state and provinces in multiple wars. Breakaway nations, former territories of the Viceroyalty, such as the Banda Oriental, Paraguay and Upper Peru, were involved to varying degrees. Foreign powers such as the British and French empires put heavy pressure on the fledgling nations during international war.

José Fructuoso Rivera y Toscana (17 October 1784 – 13 January 1854) was a Uruguayan general and patriot who fought for the liberation of Banda Oriental from Brazilian rule, thrice served as President of Uruguay and was one of the instigators of the long Uruguayan Civil War. He is also considered to be the founder of the Colorado Party, which ruled Uruguay without interruption from 1865 until 1958. He made a controversial decision to almost completely eliminate the native Charrúa during the 1831 Massacre of Salsipuedes.

The Portuguese conquest of the Banda Oriental was the armed-conflict that took place between 1816 and 1820 in the Banda Oriental, for control of what today comprises the whole of the Republic of Uruguay, the northern part of the Argentine Mesopotamia and southern Brazil. The four-year armed-conflict resulted in the annexation of the Banda Oriental into the United Kingdom of Portugal, Brazil and the Algarves as the Brazilian province of Cisplatina.

The belligerents were, on one side, the "Artiguistas" led by José Gervasio Artigas and some leaders of other provinces that made up the Federal League, like Andrés Guazurary, and on the other, the troops of the United Kingdom of Portugal, Brazil and the Algarves, directed by Carlos Frederico Lecor.

The Treinta y Tres Orientales (English: Thirty-Three Orientals or Thirty-Three Easterners) was a revolutionary group led by Juan Antonio Lavalleja and Manuel Oribe against the Empire of Brazil. Their actions culminated in the foundation of modern Uruguay. They became famous by the name of the Treinta y Tres Orientales when, in 1825, they began an insurrection for the independence of Oriental Province, a historical territory encompassing modern Uruguay and part of modern Brazilian Rio Grande do Sul State, from Brazilian control.

The group was also known as the Thirty Three Immortals.

The Battle of Sarandí was fought on 12 October 1825, in the vicinity of the Arroyo Sarandí in Uruguay, between troops of the Banda Oriental (now Uruguay) and the Empire of Brazil. It resulted in a decisive victory for the Orientals.