During the siege, shootings were frequent between the patriotic garrison, ships and outposts that harassed the defenders. On July 24, a parliamentarian received in the square the proclamations of independence of General San Martín, which unsuccessfully sought to win the royalist garrison to the patriot cause. Due to the unsuccessful result of this proposal, that same night the Cochrane's fleet attacked the port, setting fire to two smaller ships and taking three. The fighting continued and on August 4 the besiegers began to bomb the castles with
obuses, repeating this operation every night until the 14th in order to keep the royalist soldiers fatigued and demoralized. That same day, General
Juan Gregorio de las Heras led a daring ground attack on the plaza. The plan was for 150 horsemen and 1,000 infantrymen to race from their barracks in
Bellavista and overrun the fortress gates before they could be lifted. The plan ended unsuccessfully. However, the patriot cavalry managed to kill or capture the soldiers who had not managed to enter the fortress. Because of this, the patriots had 27 casualties while the royalists 41, with Colonel
Mariano Ricafort being wounded and taken prisoner.
Canterac's incursion into Lima Meanwhile, from Cuzco, Viceroy La Serna had planned an incursion on the Lima valley, which, led by General
José de Canterac, commanding 3,100 soldiers and 9 artillery pieces, left
Jauja at the end of August. After crossing the Andean mountain range in a difficult journey and having to face the
montoneros, the troops reached the outskirts of the capital on September 8, where they found the patriot army maintaining defensive positions. Although San Martín had a superior army based on the number of troops, he decided not to attack despite the insistence of General Las Heras, thus allowing Canterac to march until he entered Callao. After holding a war junta in Callao, Canterac chose to return to the mountains. His men left the fortresses with enthusiasm and cheering the
king because they believed that they were going to fight, however, as they turned north, crossed the
Rímac river and saw themselves facing the painful prospect of crossing the mountain range again, demoralization spread in the royalist army, as desertions increased to alarming levels. Despite their success against San Martín's troops that had sent in pursuit under the command of General
Guillermo Miller, upon returning to Jauja, the army was seriously reduced in number and supplies. ==End of the siege==