The armies that were about to face each other exhibited a significant disproportion. While Belgrano's
cavalry outnumbered the royalists' two-to-one, Pezuela had twice as much infantry and 18 pieces of
artillery, against only eight short-range guns carried by Belgrano's troops. At dawn of 14 November the royalists began their descent from their high position and by mid-morning they had deployed the core of their forces on the plain. Belgrano's troops were meanwhile attending
Mass, even if aware of the enemy movements. Some officers suggested to Belgrano an early cavalry assault on the enemy troops as these were still negotiating the steep terrain of the mountain slope, but the general opted for a head-on action on the plain. An hour later, Pezuela had completed his maneuver; instead of pushing a frontal assault, the royalist army outflanked the patriots on their right, crossing a range of hills that hidden them from their enemy and forcing Belgrano to hastily redeploy his troops in that direction. In the opinion of then Lieutenant
Gregorio Aráoz de Lamadrid, one of Belgrano's best officers, this move proved decisive for the outcome of the battle. Then, Pezuela's artillery opened fire, blasting holes in the patriot ranks. In a hail of enemy fire, Belgrano ordered the advance of his infantry and cavalry toward the enemy right flank, but they could not overcome both the rugged terrain and Pezuela's entrenchments. To make matters worse, Belgrano' light guns were no match for the royalist artillery. Belgrano was forced to retreat. By a trumpet call and waving the United Provinces flag on the top of a hill, he managed to gather some 500 men, leaving around 300 dead, 200 injured, 600 prisoners and almost all his guns on the battlefield. Three
mulatto auxiliary women, María Remedios del Valle and her two daughters, became famous for their efforts to provide water to the troops and assist wounded soldiers on the battlefield in spite of the heavy royalist bombardment, and they are since remembered as the
Niñas de Ayohuma ("Maidens of Ayohuma") in Argentina. ==Aftermath==