On the 3rd August, Mackenna established a battery of six guns, at four hundred and fifty yards from the trenches. The following morning Sanchez made a vigorous sally but was driven back. The same afternoon he made another attack upon a reserve battery, under the fire of his own redoubts, a ball from which blew up the ammunition of the battery, causing great confusion. Carrera ordered the battery to be abandoned, but his officers disobeyed him, and O'Higgins coming up to the rescue, the enemy was again repulsed.
The losses were considerable on both sides, but the sufferings of the besiegers were augmented by the inclemency of the weather. A convoy of ammunition for Carrera was intercepted by Royalist guerillas, thirty miles from the encampment, and delivered to Sanchez, whose supplies were running short. On the 5th Sanchez made another attack upon the advanced battery, which was bravely repelled by Luis Carrera. The Patriot general then ordered an assault upon the town, which was beaten off by the townspeople themselves. The spirit of the Patriot army was broken, deaths and desertions greatly reduced their numbers. Carrera summoned the garrison to surrender. Sanchez replied by proposing an armistice, during which the Patriots should recross the Maule. A council of war was called, and against the advice of Mackenna the siege was raised. On the 14th August the Patriot army encamped on the banks of the Itata, and from this moment their cause declined.
Carrera again fell into the error of dividing his army. He posted one division near the mouth of the Itata, under command of his brother Juan José, to protect the line of the Maule, and O'Higgins was despatched with a weak division to secure the frontier on the Bio-Bio. With the rest of his forces he went to Concepcion, while his guerillas scoured the country in every direction. This was just what suited Sanchez, who could do nothing with a strong force in front of him. He had plenty of irregulars who knew
