Ignoring the terms of the constitution, the provinces had already begun to reject the supremacy of Buenos Aires, when the outbreak of a struggle with Brazil forced the contending parties for a while to unite in the face of the common enemy.

As before, the object of international dispute was the region of the Banda Oriental.

The rule of Brazil had not been oppressive, but the people of its Cisplatine Province, attached by language and sympathy to their western neighbors, longed nevertheless to be free of foreign control.

In April, 1825, a band of thirty-three refugees arrived from Buenos Aires and started a revolution which spread throughout the country.

Organizing a provisional government, the insurgents proclaimed independence of Brazil and incorporation with the United Provinces of La Plata.