With a major effort Lavalleja was able to muster a force of similar strength, and faced the Brazilian army at the tips of the Sarandí creek, in an area located in what is now the Florida Department, on 12 October 1825.

Lavalleja formed his troops in a battle line facing south, occupying the heights overlooking the road to Paso de Polanco del Yí.

Meanwhile, the Imperial troops had reached Sarandi del Yí, and believing that Rivera was on the right bank of the Sarandí creek were surprised to see them the other side.

The manoeuver of the Brazilian Army put Lavalleja off balance, forcing him to change his front from the south to the west, but the speed with which the maneuver was carried out caused confusion in the line, leaving Zufriategui in the center and Manuel Oribe at the right.

The General Congress which gathered in the city of Buenos Aires approved on October 24 a law that reunited the Banda Oriental to the United Provinces of Rio de la Plata.

For this reason, the Orientals took action to regain control of this area, culminating in the capture of the Fortress of Santa Teresa on 31 December 1825 which was located in the Rocha Department, near the present border with Brazil.