Platine War

The Platine War (18 August 1851 – 3 February 1852) was fought between the Argentine Confederation and an alliance consisting of the Empire of Brazil, Uruguay and the Argentine provinces of Entre Ríos and Corrientes. The war was part of a long-running contest between Argentina and Brazil for influence over Uruguay and Paraguay, and hegemony over the Platine region (areas bordering the Río de la Plata). The conflict took place in Uruguay, on the Río de la Plata, and northeastern Argentina.

In 1850, the Platine region was politically unstable. Although the governor of Buenos Aires, Juan Manuel de Rosas, used his position to gain dictatorial control over other Argentine provinces, his rule was plagued by a series of regional rebellions. Meanwhile, Uruguay struggled with a long-running civil war which started after acquiring independence from Brazil in 1828. Rosas backed the Uruguayan Blanco party in this conflict, and further desired to extend Argentine borders to areas formerly occupied by the Spanish Viceroyalty of the Río de la Plata. This meant asserting control over Uruguay, Paraguay, and Bolivia. Rosas' objective also threatened Brazilian interests and sovereignty since the old Spanish Viceroyalty had also included territories which had since been assimilated into Brazil's province of Rio Grande do Sul.

Brazil actively pursued ways to eliminate the Rosist threat. In 1851, it allied with the Argentine breakaway provinces of Corrientes and Entre Rios (led by Justo José de Urquiza), and the anti-Rosas faction in Uruguay. Brazil next secured the northern flank by signing defensive alliances with Paraguay and Bolivia. Faced with an offensive alliance against his regime, Rosas declared war on Brazil. Allied forces then advanced into Uruguayan territory, defeating the Rosas-aligned faction led by Manuel Oribe. Afterwards, the allied army was split, with the main arm advancing by land to engage Rosas's main defenses and the other launching a seaborne assault directed at Buenos Aires.

The Platine War ended in 1852 with the allied victory at the Battle of Caseros, establishing Brazilian hegemony over much of South America. The war's result further ushered in a period of economic and political stability in the Empire of Brazil. With Rosas gone, Argentina began a process which would result in a more unified state. However, the end of the war did not completely resolve other issues within the Platine region. Turmoil continued in subsequent years, with internal disputes among political factions in Uruguay, a long civil war in Argentina, and an emergent Paraguay asserting its claims. Two more major international wars followed during the next two decades, sparked by territorial ambitions and conflicts over influence.