Federal League (1815–1820)

In 1810, Spain moved the headquarters for the Viceroyalty of the River Plate to Montevideo after the May Revolution forced them to abandon Buenos Aires. On February 15, 1811 José Gervasio Artigas left his home of Montevideo and moved to Buenos Aires to offer his military services. The people of Spanish America were fighting for their freedom and Artigas wished to defend these ideals in the Eastern Bank. At the beginning of April he returned to his country with approximately 180 men provided by the Government of Buenos Aires; on April 11, he issued the Mercedes Proclamation, assumed control of the revolution and on May 18 defeated the Spanish in the Battle of Las Piedras. He then began the siege of Montevideo and was acclaimed as The First Chief of the "Orientals" (the first names of current Uruguay being Banda Oriental (Eastern Bank) and later Provincia Oriental (Eastern Province), Uruguayans thus refer to themselves as 'Orientales').

He soon turned against the government of the United Provinces of the Río de la Plata and in 1814 he organized the Unión de los Pueblos Libres (Union of the Free Peoples), of which he was declared Protector. In the following year, as a federalist, he liberated Montevideo from the centralizing control of the "Unitarians" from Buenos Aires, and in 1815 declared the Liga Federal. In this Congress Artigas ratified the use of the flag created by Manuel Belgrano (which would later become the flag of the Argentine Republic), but added a diagonal festoon in red, red being the sign of federalism in Argentina at that time.[1] Original member provinces were the present-day Argentinian provinces of:

• Córdoba (with La Rioja)
• Corrientes
• Entre Ríos
• Misiones
• Eastern Province (Uruguay)
• Santa Fe.

The constant growth of influence and prestige of the Federal League frightened Buenos Aires (due to its federalism) and Portugal (because of its republicanism), and in August, 1816 the latter invaded the Eastern Province with the intention of destroying the protector Artigas and his revolution.

The Portuguese forces, led by Carlos Frederico Lecor, thanks to his numerical and material superiority, conquered the Eastern Province and took Montevideo on January 20, 1817, but the struggle continued for three long years in the countryside. Infuriated by Buenos Aires's passivity, Artigas declared war on the Supreme Directorship at the same time that he faced the Portuguese with armies that were being decimated by successive defeats. Without resources and without suitable men for the struggle, Artigas finally retreated to Entre Ríos Province, across the Uruguay River.

In 1820, governors Francisco Ramírez and Estanislao López, of Entre Ríos and Santa Fe provinces respectively, both members of the Federal League, managed to end victorious the struggle against the centralism of Buenos Aires, defeating a diminished Supreme Directorship army at the Battle of Cepeda and signing a federal agreement with Buenos Aires Province. As these Provinces, and Corrientes Province, rejoined the United Provinces of the Río de la Plata, the Federal League effectively came to an end as a separate political entity.

The Treaty of Pilar resulted unacceptable to Artigas so he ordered Ramírez and López to renounce it, but they disobeyed. Because of this, Artigas entered into conflict with his former ally Governor Francisco Ramírez, who defeated the remnants of Artigas' army. Artigas withdrew to Paraguay, where he settled as an exile until his death.[2] The Eastern Province was annexed by Portugal to its Brazilian dependences in 1821.