[1] In 1811, José Gervasio Artigas, who became Uruguay's national hero, launched a successful revolt against Spain, defeating them on 18 May in the Battle of Las Piedras.

The constant growth of influence and prestige of the Federal League frightened the Luso-Brazilian Monarchy (because of its republicanism), and in August 1816 they invaded the Banda Oriental, with the intention of destroying the protector and his revolution.

In 1821, the Provincia Oriental del Río de la Plata (present-day Uruguay), was annexed as a province into the Kingdom of Brazil under the name of Cisplatina.

"As a reaction, a group of Uruguayan insurgents, the Thirty-Three Orientals, led by Juan Antonio Lavalleja, declared independence on 25 August 1825, supported by the United Provinces of the Río de la Plata, which planned to reannex the region.

Despite the Argentine victory in the battle of Ituzaingó, neither side gained the upper hand and, on 27 August 1828, the Preliminary Peace Convention, fostered by the United Kingdom through the mediation of diplomat John Ponsonby, was signed between the Empire of Brazil and the United Provinces, giving independence to the Cisplatina province as the Oriental Republic of Uruguay, and – more importantly to planned British interests – establishing the international status of the Río de la Plata, so that international trade was easier to accomplish.