In 1825 the provinces were represented at a general constituent congress which assembled in Buenos Aires. After much discussion the unitarians, with Rivadavia at their head, finally obtained control. In 1826 he was elected executive chief of the federation. This election, however, did not make him president in fact. Recognition from the Cabildos and the caudillos was practically of greater importance than the vote of a congress of delegates who were unable to insure the acquiescence of their constituencies. Rivadavia's favourite plan of placing the city of Buenos Aires directly under the control of the central government excited bitter opposition among the federalists of Buenos Aires. Under their leader, Manuel Dorrego, they protested vehemently against the dismemberment of their home province. Meanwhile the crazy fabric was subjected to the strain of a serious foreign war. In 1825 the country districts of Uruguay rose against their Brazilian rulers. The Argentines went wild with joy when they heard of the victory which the gauchos won over the imperial forces at Sarandi. Congress promptly decreed that Uruguay had reunited herself to the confederation. The Emperor's answer was a declaration of war and a blockade of Buenos Aires. The fighting Irish sailor, Admiral William Brown, again came to the front, and his daring seamanship rendered the Brazilian blockade ineffective. He destroyed a large division of their fleet at the battle of Juncal, while fast Baltimore clippers, commanded by English and Yankee privateer captains, swept Brazilian commerce from the seas. Late in 1826 an Argentine army of eight thousand men was assembled for the invasion of Rio Grande do Sul. Alvear, now returned from exile, was entrusted with its command, and on the 20th of February, 1827, the Brazilians were overwhelmingly defeated at Ituzaingo, far within their own boundary. The Argentines were not able to follow up their victory, and shortly returned to Uruguayan territory, but the Emperor was never again able to undertake an aggressive campaign. Negotiations for peace were begun, and Rivadavia's envoy signed a treaty by which Uruguay was to remain a part of the empire of Brazil. A storm of indignation broke forth at Buenos Aires, and Rivadavia had to disavow his minister and continue the war. The blow to his prestige was, however, mortal; the federalists had, indeed, never ceased to make war against him; and the unitarian constitution which Congress had adopted at his dictation was rejected unanimously by the provinces. He resigned, and Dorrego, chief of the unitarians, succeeded him as nominal executive chief of the confederation. In reality, however, the Republic was divided into five quasi-independent military states. Dorrego ruled in Buenos Aires, Lopez in Santa Fe, Ibarra in Santiago, Bustos in Cordoba, and Quiroga in Cuyo.