In August, 1826, the famous Argentine general, Carlos Alvear, took command of the patriot forces. Jealousies and quarrels had meantime broken out between Lavalleja and Rivera. Alvear took the former's side and Rivera's partisans revolted. But the arrival of more re-enforcements for the Brazilians hushed up for the moment the intestine quarrels of the Spanish-Americans. Alvear determined to carry the war into Brazil, and early in January, 1827, succeeded in passing between the northern and southern Brazilian armies, and penetrated across the frontier to the north-east. He had sacked Bage, the principal town of that region, before the Brazilian general, the Marquis of Barbacena, was able to concentrate his forces and start in pursuit. Alvear turned north toward the Missions, but he was in a hostile country where defeat meant total destruction. Though his army numbered eight thousand men he had cut himself off from his base, and an enemy in equal force was close at his heels. He resolved to turn and give battle, and on the 20th of February, 1827, his army met that of Barbacena in the decisive battle of Ituzaingo, which ended in the defeat of the Brazilians. Although Barbacena was able to withdraw his army without material loss, and Alvear retired at once to Uruguayan soil, the Brazilians were never afterwards able to undertake a vigorous offensive. The result of that battle insured that the north bank of the Plate should remain Spanish in blood, language, and government. A few days before Ituzaingo, Admiral Brown had won the great naval fight of Juncal at the mouth of the river Uruguay, and thenceforth the Brazilian blockade of Buenos Aires was entirely ineffective. If it had not been for the civil disturbances in Argentina that paralysed the Buenos Aires government, the Brazilians might have been swept out of Montevideo at the point of the sword, and the Argentines might have undertaken the conquest of Rio Grande itself. Though considerable Argentine forces remained in Uruguay during 1827 and 1828, they put no vigour into their operations, and on their part the Brazilians were able to do little more than hold Montevideo. So hampered was Rivadavia, the president of Buenos Aires, by revolts, uprisings, and disorders throughout Argentina that he thought himself obliged to agree to abandon Uruguay. Public opinion in Argentina would not accept the treaty which he made; he was deposed, and a leader of the opposite party installed in power.