Uruguay declares independence from the Empire of Brazil

Background. Prior to 1825, the Banda Oriental was annexed by Brazil as Cisplatina. The United Provinces of the Río de la Plata sought control of the region, sending failed diplomatic missions in 1823. A separatist movement in 1822–1823 was subdued by Brazilian forces. The conflict arose from competing claims over the territory, with the United Provinces viewing Cisplatina as rightfully theirs.

Declaration of Independence. On 19 April 1825, the Thirty-Three Orientals landed at Agraciada beach. Their expedition attracted local support and reached Montevideo by May. On 25 August 1825, an assembly in Florida declared independence from Brazil and union with the United Provinces. The United Provinces recognized this incorporation in October 1825, prompting Brazilian military response.

Outbreak of War. Brazil declared war on the United Provinces on 10 December 1825. Admiral Rodrigo Lobo imposed a naval blockade on the River Plate. The United Provinces authorized privateers in February 1826. The conflict involved naval engagements and invasions, including the capture of Santa Teresa by the Orientals in December 1825.

Resolution. Neither side gained a decisive upper hand. Under British mediation, the Treaty of Montevideo was signed in 1828, acknowledging the independence of Cisplatina as the Eastern Republic of Uruguay. This resolution ended the Cisplatine War and established Uruguay as an independent state.