[3] In 1810, the May Revolution had forced the Spanish to abandon Buenos Aires, but they held on to the Banda Oriental (present-day Uruguay), as Francisco Javier de Elío moved the headquarters of his Viceroyalty of the Río de la Plata to Montevideo.

In May 1811, the revolutionary José Gervasio Artigas defeated the Spanish in the Banda Oriental at the Battle of Las Piedras.

After the battle, the Royalists only remained in control of two cities: Colonia del Sacramento and Montevideo, which was besieged by Artigas and José Rondeau.

Montevideo had formidable fortifications and the Spanish controlled the Río de la Plata river.

He broke relations with Buenos Aires, and lifted the blockade over Montevideo in October 1811.