The grenadiers left the convent at dawn, preparing their formations behind the convent. San Martín returned to the tower to watch the enemy who disembarked at sunrise, 5:30 in the morning. He mounted his horse, gave a short harangue to the troops, and headed to battle. His strategy was to divide his cavalry forces into two
columns, of nearly sixty horsemen each, and make a surprise
pincer movement to trap the enemy forces. The cavalry would not use their guns, relying instead on
sabre and spear attacks. The right-hand column was headed by
Justo German Bermúdez, and the left-hand one by San Martín. The royalists marched in two columns with the two cannons, a deployed flag and
military drummers. The
clarion of the Regiment of Mounted Grenadiers sounded for the first time, marking the beginning of the battle. San Martín's column was the first one to reach the enemy. The two cannons and the cannon fire from the ships supported the royalists, but they were quickly outmanoeuvred by the sabre charges and, unable to form a
square, had to retreat. The advantage of surprise and the speed of the cavalry charge allowed the regiment to defeat the larger royalist army who had almost double their number of soldiers. When Bermúdez and his column joined the battle the royalists were not able to stand their ground and were
routed, retreating in disarray under covering fire from the ships. Bermúdez led the attack at this point as San Martín had
fallen from his horse. San Martín did not mention Escalada in his first battle report, initially leading historians to infer that they stayed within the convent during the battle. However it is currently considered that they took part in the battle, as suggested by the royalist battle report and a later report from San Martín which clarifies that only twelve grenadiers stayed in the convent. The combat took around fifteen minutes and left forty royalists dead and many injured, including Zabala. Fourteen patriot grenadiers died in the combat and two more would die afterwards due to combat injuries.
Manuel Díaz Vélez fell from his horse in the gully, was mortally injured and captured by the royalists. Bermúdez was shot in the
patella and died a few days later.
Hippolyte Bouchard captured the Spanish flag after killing the
standard-bearer.
Cabral's intervention , trapped under his dead horse during the battle, is saved by
Juan Bautista Cabral Despite the victory, the remaining royalist forces could not be pursued as the column led by Justo Bermúdez had moved further than calculated for. This delayed the meeting with San Martín's column whose horse was killed by enemy fire, leaving with his leg trapped under the corpse of the animal. These factors led to the columns not meeting up and allowed many royalists to escape. A royalist, probably Zabala himself, attempted to kill San Martín while he was trapped under his dead horse where he suffered a sabre injury to his face, and a bullet wound to his arm.
Juan Bautista Cabral and
Juan Bautista Baigorria intervened and saved San Martín's life. Cabral was mortally wounded during the rescue and San Martín reported that after Cabral was hit he said "I die happy, we have defeated the enemy". The exact moment this was said is unclear as the word
after could have meant immediately after; during the ongoing battle; or some hours later during Cabral's agonising decline. San Martín wrote the battle report under a nearby tree. Fray Herminio Gaitán considers that Cabral's last words would have been in the
Guaraní language, his
first language, and that as San Martín also spoke Guaraní he would have translated them for the battle report. Juan Bautista Cabral is commonly known as "Sergeant Cabral", but he was a
private at the time of the battle. San Martín's report mentions him as "the grenadier Juan B. Cabral", and historians like
Bartolomé Mitre,
Herminio Gaitán,
Gerardo Bra and
Norberto Galasso support the idea. Mitre considers that Cabral was
promoted posthumously, but there are no documents confirming that. ==Aftermath==