San Martin's tactical dispositions were admirably made on the momentous morning of April 5, 1818. He divided his army into two divisions and a reserve, stationing the latter on the extreme east of his line. Under cover of a heavy artillery fire the west division rushed down the slope, across the bottom, and up the hills commanding the Valparaiso road. The counter-charge of the Spanish horsemen was repulsed by the superior patriot cavalry, and the Spanish west wing was isolated from the rest of the army. Meanwhile the patriots' east division, composed of the bulk of their infantry, had charged straight across the narrow part of the bottom and reached the high ground opposite without seeing an enemy, but there was met by a terrific charge from the royalist infantry, and rolled in confusion back down the hill. Regardless of the artillery fire, the Spaniards were pursuing triumphantly over the low ground, when suddenly their eastern flank received the charge of the patriot reserve, which had advanced obliquely from its original position on the extreme east. This movement decided the battle. The Spanish infantry could not re-form to meet it, and were rolled up in helpless confusion. The flying patriot infantry rallied and returned to the attack; their cavalry, already victorious at the other end of the line, turned and charged the west flank of the Spaniards, who, simultaneously taken at both ends and in front, were cut down by hundreds. A few managed to keep their formation and fell back to the farm of Espejo, behind whose extensive buildings and garden walls they entrenched themselves, determined to sell their lives as dearly as possible. Joined by their left wing, which, unable to reach the centre where the hard fighting had taken place, had suffered little loss, they withstood the attack of the victorious patriot army. But the artillery was brought up, the walls knocked to pieces, and the position carried in the midst of the most frightful carnage. The infuriated patriots gave no quarter until General Las Heras rode among them and begged them to desist from the inhuman slaughter. Maipo was the hardest fought battle in all the wars of South American independence. Of five thousand royalists, twelve hundred were killed, eight hundred wounded, and two thousand two hundred made prisoners. Only eight hundred escaped, flying south toward safety at Talcahuano, of whom less than a hundred held together until they reached the Spanish fortifications. Of the patriots more than a fifth were killed and wounded--the greatest sufferers being the freed negroes whom San Martin had recruited in the Argentine. Half of these brave fellows were left on the field.