The Battle of Ituzaingo or Passo do Rosário was fought in the vicinity of Santa Maria River, in a valley of small hills where a stream divided the land in two. The stream itself was a branch of the river and according to the sources, was five to six feet deep, giving passage where it became narrower.
On this place, Alvear established a strong position on the western bank by placing Lavalleja's cavalry at the vanguard on February 18, 1827. The following day, the Imperial Army reached the place by the beginning of the night. The troops were exhausted by the long march, but the preparative for the fight went on. Rejecting some officers advice about the soldiers exhaustion, Barbacena and his chief of staff Field Marshall Henrique Brown, were uneasy to attack. Believing that his force was facing the rear of the Republican Army and that Alvear was retreating, Barbacena planned to take Lavaleja's position by storm at day-break of the 20th.
The description of the battle vary widely depending on the author. The only thing they agree is that the Brazilian Army opened the attack.
In fact there is hardly any point of agreement about the fight. The sources disagree even about the time of the first attack. For some it was five o'clock in the morning, others believe it was six o'clock A.M. when it started. A last group put it at seven o'clock in the morning. The battle duration is also motive of disagreement. The majority believe it lasted six hours, while others reckon it on seven.
Nonetheless, the main cause of misunderstanding is about the force of the two armies. Alvear troops are calculated from 6,200 to 10,000, while the Imperial Army vary from 6,100 to 10,500. According to a text written by an anonymous witness (probably a Prussian soldier who fought on the Brazilian side), the two armies were equivalent, with a slight superiority in number to the Imperial Army. A reliable figure could be some 7,000 to 8,000 to the Republican Army and 7,500 to 9,000 to the Army of the South.
Alvear's order of battle was the following: on the vanguard the 1st Corps of 2,200 cavalrymen led by Lavalleja held the right of the republican position. To the left, on the center, the 2nd Corps commanded by Alvear with cavalry units of unknown size. Finally, the center-left was held by 3,150 men of the 3rd Corps with cavalry and infantry units. The commander of this corps was General Miguel Estanislao Soler, who also held the bulk of the artillery pieces. Both, Alvear and Soler were deployed backward, out of sight of the enemy. During the night of the 19th, the 2nd and 3rd corps marched slowly to forward positions.
On the other side of the stream, Barbacena deployed his army. On the right he had the 1st Infantry Division  with some  cavalry units commanded by General Sebastião Barreto Pereira. On the center, the 2nd Division led by General João Crisóstomo Calado with calvary and infantry units. The left was held by the Volunteers Corps, commanded by field Marshall José de Abreu, Baron of Cerro Largo.
General Pereira opened the battle by sending his cavalry and infantry to cross the stream in order to attack the position held by the  artillery of 1st Corps under colonel Felix Olazabal. As soon as the 1st Division managed to cross the stream, it found itself under fire of the enemy artillery. Notwithstanding, the Brazilians continued to advance. Lavalleja's cavalry tried to block the passage of the 1st Division, but ,outnumbered, they soon began to be pushed back. At the same time, 400 cavalrymen under Colonel Bento Gonçalves, positioned on the extreme right of the Imperial Army, moved to encircle Lavalleja's position. On the left, the Volunteers Corps crossed to the west bank to close the encirclement. Barbacena was still unaware of Alvear units in the nearby.
At this moment, Alvear sent part of his cavalry under colonel Julian Laguna to stop the enemy offensive on his right, while he would led the 2nd Corps in a frontal assault on the 2nd Division. Soler, for his turn, launched a counterattack with the finest cavalry units under Alvear command against the 1st Division, while,  at the same time, backed the 2nd Corps in the  frontal assault on the 2nd Division. As Alvear planned, the fight became a cavalry battle, where his restful forces would be in advantage, facing an enemy that spent the previous day marching. Only then Barbacena noticed that Alvear misled him.
With Laguna's aid, Lavalleja turned to face the Volunteers Corps. The extreme left of the the Imperial Army  soon collapsed under his assault. The troops on this sector of the battlefield were all formed by militia infantry units with modicum training. Despite, Cerro Largo desperate attempt to keep his men on the battlefield, they panicked and fled.
The 2nd Division which was moving to the right in order to give support to general Pereira, had to stop moving and make a firm stand against Alvear cavalry.
The 2nd Division, however, maintained a vigorous resistance thoughout  the struggle. Alvear tried repeteadelly frontal assaults, but he was expelled by heavy fire of the infantry. When Lavalleja's 1st Corps secured a footing on the Brazilian side of the bank and marched to the rear of the Imperial army, general Calado decide to withdraw. Barbacena forces were leaving the battlefield. The infantry, however; continued to keep the enemy cavalry at a secure distance.
Meantime, the extreme right of the Brazilian Army led by Colonel Bento Gonçalves were under attack of superior forces commanded by Colonel Juan Gallo Lavalleja. After little combat, Bento Gonçalves withdrew.
The two enemies were in bad conditions when the fight was over.Notwithstanding, the Republican Army achieved a great victory where cavalry proved to be decisive. Barbacena's army suffered great losses, perhaps a number between 800 and 1,300 men were killed, wounded or captured (200 dead, while the most part was captured). The Republican Army losses totaled a number between 400 and 560 (141 killed) according to an Argentinean source. These figures  in terms of dead are almost certain underestimated. Many soldiers died of wounds on both sides. If we take under consideration the fact that the Republican Army set fire on the surrounding area of the battlefiled  before the last part of the Imperial Army left the battle,  many more soldiers could have died.
The battle while important for land operations, ended without a decisive victor. The Republican Army had no logistic to explore the gaps after the struggle. The Imperial moved to the rear with scarce problems. Besides, at sea, the naval supremacy of the Imperial Navy forced an agreement between Buenos Aires and the empire. Thanks to that, Uruguay achieved its  independence in 1828.  Nevertheless, after Ituzaingo the war continued for a year yet. With both sides forces widely scattered, the war was raged by small groups and detachments where victory favoured one side or the other, but with no results for the campaign.
While Uruguay conquered its independence, political stability for this small country was still a long path. Argentina, for its turn would face many troubles within the confederacy. Finally, in Brazil the War of Cisplatine along with many internal revolts led  D. Pedro I to resign in 1831. Political instability would mark the three young countries for some time.                                                                                                                              Ituzaingo image