According to the Chilean agents who returned from the negotiations, the Peruvian forces amounted to 4,136 men on July 11, distributed as follows: 2,036 in Lima, 900 in Callao, and 1,200 in Pativilca.

[6] Aware of the Chilean arrival, General Orbegoso concentrated his forces in Chancay for the defense of the capital, while the Restoration Army began their advance towards Lima.

At noon on August 21, by order of Bulnes, the restorers advanced to the Palao estate since he wanted to avoid a direct clash with the Orbegozo positions.

On August 18, 1838, the restorers occupied the Concha farm and extended their lines to La Magdalena, for which it was necessary to garrison the Lima portals of Juan Simón and Guadalupe, while the gate of Callao was defended by Nieto and that of Monserrate by Vidal.

General Orbegoso, who had gone to the outskirts of Lima from Nieto's position, immediately gathered his forces, which were distributed along the wide road that connects La Legua with the Callao gate.

At 02:30 in the afternoon, after having crossed a long gorge, the Restoration Army's vanguard, preceded by 25 jägers on horseback and commanded by General Ramón Castilla, reached a rocky area when they were attacked by enemy guerrillas.

With the counterattack of the squadrons of lancers and jägers, the Restoration Army managed to continue its advance to Guías, but after an hour and a half of fighting, they ran out of ammunition.

At that time they received the reinforcement of the 1st Restoration Division, whose Carampangue and Colchagua battalions, with the support of 2 artillery pieces, charged into the center of the north-Peruvian line.

The fight was extraordinary violent, since the restoration troops felt the fire from the front, from the flanks and from the surrounding buildings, maintaining this situation for a long time.

Unable to rebuild or withdraw, Bulnes ordered Colonel Pedro Godoy, forcing the bridge that connects Malambo with Lima, to pursue them with the 2nd division, with which a massive bayonet charge was made, achieving at 08:30 the occupation of the Plaza Mayor.

[11] The occupation of Lima allowed the validity of the Peruvian Constitution of 1834 to be restored and the election of the Great Marshal Agustín Gamarra as provisional president of Peru[d] by decision of a meeting of neighbors, on August 24, 1838.

As for Orbegoso's army, several of those dispersed from the battle of Guías would take refuge in the Callao fortress, others would escape to the outskirts of Lima to form guerrillas to face the restorers.

[13] Now, Bulnes and Gamarra would have to face, in the meantime, three problems that were difficult to solve: The siege of Callao, the fight against the guerrillas around the capital and the increase in the army with the formation of Peruvian units.