and sought to restore Oribe in power. Rivera and Juan Lavalle prepared troops to attack Buenos Aires. Both British and French troops intervened, initiating the Uruguayan Civil War, or Guerra Grande (Great War). Manuel Oribe was eventually defeated in 1851, leaving the Colorados in full control of the country. Brazil followed up by intervening in Uruguay in May 1851, supporting the Colorados with financial and naval forces. In February 1852, Rosas resigned, and the pro-Colorado forces lifted the siege of Montevideo. Uruguay rewarded Brazil's financial and military support by signing five treaties in 1851 that provided for perpetual alliance between the two countries. Montevideo confirmed Brazil's right to intervene in Uruguay's internal affairs. The treaties also allowed joint navigation on the Uruguay River and its tributaries, and tax exempted cattle and salted meat exports. The treaties also acknowledged Uruguay's debt to Brazil for its aid against the Blancos, and Brazil's commitment for granting an additional loan. In addition, Uruguay renounced its territorial claims north of the Quaraí River, thereby reducing its area to about 176,000 square kilometers, and recognized Brazil's exclusive right of navigation in the Lagoa Mirim and the Jaguarão River, the natural border between the countries. Paraguayan War In 1855, new conflict broke out between the parties. It reached its high point during the Paraguayan War. In 1863, the Colorado general Venancio Flores organized an armed uprising against the Blanco president, Bernardo Prudencio Berro. Flores won backing from Brazil and, this time, from Argentina, who supplied him with troops and weapons, while Berro made an alliance with the Paraguayan leader Francisco Solano López. When Berro's government was overthrown in 1864 with Brazilian help, López used it as a pretext to declare war. The result was the Paraguayan War, a five-year conflict in which Uruguayan, Brazilian and Argentinian armies fought Paraguay, and which Flores finally won, but only after great loss of his own troops. Flores did not enjoy his militar success for long. In 1868, he was murdered on the same day as his rival Berro. Both parties were weary of the chaos. In 1870, they came to an agreement to define spheres of influence: the Colorados would control Montevideo and the coastal region, the Blancos would rule the hinterland with its agricultural estates. In addition, the Blancos were paid half a million dollars to compensate them for the loss of their stake in Montevideo. But the caudillo