on both sides of the border had long been antagonistic toward Berro's policies. The Uruguayan president attempted to tax the cattle coming from Rio Grande do Sul and to impose curbs on the use of Brazilian slaves within Uruguayan territory; slavery had been outlawed years before in Uruguay. Among the Brazilian land barons were David Canabarro and Antônio de Sousa Neto, both allies of Flores and former separatist rebels during the Ragamuffin War that had ravaged Rio Grande do Sul from 1835 until 1845. Canabarro, a frontier military commander, misled Brazil's government by denying that Brazilians were crossing the border to join Flores. Sousa Neto went to the Brazilian capital to request immediate government intervention in Uruguay, claiming that Brazilians were being murdered and their ranches robbed. The "fact that Uruguayan citizens had just as valid claims against Brazil as Brazilians had against Uruguay was ignored", said historian Philip Raine. Although Sousa Neto had ties with the governing political party, his claims, including that he could amass a force of 40,000 to invade Uruguay, were not taken seriously by all. The Uruguayan crisis arrived at a difficult moment for Brazil, which was on the verge of a full-blown war with the British Empire for unrelated reasons. Brazil's government decided to intervene in Uruguay, fearful of showing any weakness in the face of an impending conflict with Britain, and believing that it would be better for the central government to take the lead rather than allow the Brazilian ranchers on the frontier to decide the course of events. Early engagements Brazilian ultimatum On 1 March 1864, Berro's term of office ended. The ongoing civil war prevented elections; therefore Atanasio Aguirre, president of the Uruguayan senate and a member of the Amapolas (the radical wing of the Blanco Party) replaced Berro, on an interim basis. In April, José Antônio Saraiva was appointed minister plenipotentiary by the Brazilian government and charged with quickly reaching an accord that would settle Brazil's claims and ensure the safety of Brazilian citizens. His focus soon shifted from satisfying Brazil's terms to a more immediate goal of hammering out a deal between the antagonists in the civil war, with the expectation that only a more stable regime would be able to reach a settlement with Brazil. The government in Montevideo was at first reluctant to consider Saraiva's proposals. With backing from Paraguay, it saw little advantage in negotiating