Montevideo where he joined his friend, the Chilean Jose Miguel Carrera, also exiled due to political differences with San Martin and Bernardo O'Higgins. Diplomatic missions to England, United States and Bolivia Alvear returned to Argentina in 1822 thanks to an amnesty law (Ley del olvido). At the end of 1823, Bernardino Rivadavia named him minister plenipotentiary to the United States. Before going to Washington, Alvear stopped in London and managed to get an interview with George Canning, the British Foreign Secretary. Weeks after this interview, the British government formally recognized the independence of the United Provinces of the Rio de la Plata. In 1825, together with José Miguel Díaz Vélez, Carlos María de Alvear was sent by the Buenos Aires government to Bolivia to meet with Simón Bolívar. The real objective of the so-called Alvear-Díaz Velez Mission was to seek Bolívar's support in the looming war with the Empire of Brazil, over the Banda Oriental. It was proposed that Bolívar should lead a Hispanic American alliance that can exert pressure on Dom Pedro I to withdraw his army stationed in the Eastern Province. The mission, which was created by an Act passed on May 9, 1825, gave Alvear and Díaz Vélez authority to negotiate and settle issues involving the liberation of the four provinces of Alto Peru. Alvear had also a project of his own: the creation of a big republic in South America comprising Argentina, Chile, Bolivia, Paraguay and Uruguay. He asked Bolívar to be its first president. The Venezuelan leader was sympathetic to this project but dissensions in Gran Colombia forced him to abandon it. War against the Empire of Brazil To neutralize Alvear's political ambitions, newly elected President Bernardino Rivadavia appointed him his Minister of War and Navy in early 1826. In a short period of time, and with limited resources, Alvear was able to raise an army of 8.000 men to wage war against the Empire of Brazil. Conflicting claims over the Banda Oriental (which included current Uruguay) pushed both countries into conflict. Victory seemed unattainable to the Argentines. At the time, Brazil had a population of close to 5 million inhabitants (including 2 million slaves), a standing army of 120.000 men and a naval fleet of almost 80 vessels. In contrast, the fledgling Argentine Republic had only 700,000 inhabitants and faced the secession of almost half of its provinces. Fearing a Brazilian invasion of Argentine