MILITARY POSITION OF THE AMERICANS AT THE END OF THE ARMISTICE—MEXICAN DEFENCES—PLAN OF ATTACK—RECONNOISSANCES OF SCOTT AND MASON—IMPORTANCE OF MEXICAN POSITION AT MOLINO DEL REY—SCOTT'S SCHEME OF CAPTURING THE CITY—BATTLE OF MOLINO DEL REY—REFLECTIONS AND CRITICISM ON THIS BATTLE—PREPARATIONS TO ATTACK CHAPULTEPEC—STORMING OF CHAPULTEPEC AND OF THE CITY GATES OF SAN COSMÉ AND BELEN—RETREAT OF THE MEXICAN ARMY AND GOVERNMENT—AMERICAN OCCUPATION OF THE CITY OF MEXICO.
At the termination of the armistice the position of the American forces was greatly changed from what it had been on the morning of the 20th of August. The occupation of San Agustin had been followed by that of Contreras, San Angel, Coyoacan and Churubusco in the course of that day, and on the next, Mixcoac and Tacubaya were taken possession of. Thus the whole southern and south-western portion of the valley, in front of Mexico, were now held by the Americans; and this disposition of their forces, commanding most of the principal approaches to the capital, enabled them, for the first time to select their point of attack.
In reconnoitering the chief outworks of the Mexicans by which he was still opposed, General Scott found that there were several of great importance. Directly north of his headquarters at Tacubaya, and distant about a mile, arose the lofty, isolated hill of Chapultepec, surrounded by its massive edifice, half castle, half palace, crowned with cannon. This point, it was known, had been strongly fortified to maintain the road leading from Tacubaya to the garita of San Cosmé on the west of the city. Westwardly, beyond the hill of Chapultepec, whose southern side and feet are surrounded by a dense grove of cypresses, and on a rising ground within the military works designed to strengthen the castle, was the Molino del Rey, or King's Mill, which was represented to be a cannon foundry to which large quantities of church bells had been sent to be cast into guns. Still further west, but near the Molino or Mill, was the fortified Casa Mata, containing a large deposit of powder.
These,—together with the strong citadel, lying near the garita of Belen in the south-western corner of the city,—were the principal external defences still remaining beyond the immediate limits of the capital. The city itself stands on a slight swell between lake Tezcoco and the western edge of the valley, and, throughout its greater extent, is girdled by a ditch or navigable canal extremely difficult to bridge in the face of an enemy, which serves the Mexicans not only as a military defence but for drainage and protection of their customs. Each of the eight strong city gates were protected by works of various character and merit. Outside and within the cross fires of these gates there were other obstacles scarcely less formidable towards the south. The main approaches to the city across the flat lands of the basin are raised on causeways flanked by wide and deep ditches designed for their protection and drainage. These causeways, as well as the minor cross roads which are similarly built, were cut in many places and had their bridges destroyed so as to impede the American's advance and to form an entangling net work; while the adjacent meadows were in this rainy season either filled with water in many places or liable to be immediately flooded by a tropical storm.
With these fields for his theatre of action, and these defences still in front of him, it was an important and responsible question, whether General Scott should attack Mexico on the west or on the south.
There can be hardly a doubt that the capture of the hill and castle of Chapultepec, before assaulting the city, was imperatively demanded by good generalship. If the capital were taken first, the Mexicans instead of retreating towards Guadalupe and the north, when we attacked and captured from the south, would of course retire to the avoided stronghold of Chapultepec; and, if our slender forces were subsequently obliged to leave the city in order to take the fortress, our sick, wounded and thinned regiments would be left to the mercy of the mob and the leperos. Chapultepec would thus become the nucleus and garrison of the whole Mexican army, and we might be compelled to fight two battles at the same time,—one in the city, and the other at the castle. But, by capturing the castle first, and seizing the road northward beyond it, we possessed all the most important outworks in the lap of the valley, and cut off the retreat of the Mexicans from the city either to the west, to the castle, or towards our rear in the valley. We obtained, moreover, absolute command of two of the most important entrances to the capital, inasmuch as from the eastern foot of the hill of Chapultepec two causeways, and aqueducts raised on lofty arches, diverged northeastwardly and eastwardly towards the city. The northernmost of these entered Mexico by the garita of San Cosmé, while the other reached it by that of Belen near the citadel.
In attacking Chapultepec, it was important to consider the value of the Molino del Rey or King's Mill, and Casa Mata, both of which, as we noticed, lie on rising ground within the works designed to protect Chapultepec. Upon examination it will be found that the Molino del Rey, or King's Mill, bears the relation of a very strong western outwork both to the castle of Chapultepec and its approaches by the inclined plain which serves to ascend its summit. As the Molino del Rey is commanded and defended by the castle, so it reciprocally, commands and defends the only good approach to the latter. [74] As long as the Molino was held by the Mexicans, it would of course, form an important stronghold easily reached from the city around the rear of Chapultepec; so that if Scott attacked the castle and hill from the south, where the road that ascends it commenced, he would be in danger of an attack on his left flank from the Mexicans in the defences at Molino and Casa Mata.
If the King's Mill fell, the result to the enemy would be that, in addition to the loss of an important outwork and the consequent weakening of the main work, its occupants or defenders would be driven from a high position above the roads and fields into the low grounds at the base of Chapultepec, which were completely commanded from the Molino, and thus the Mexicans would be unable to prevent the American siege pieces from taking up the most favorable position for battering the castle. It was important, therefore, not only that the foundry should be destroyed, but, in a stratagetic view, it was almost indispensable in relation to future operations that the position should be taken. It is undeniable, as following events showed, that the Mexicans regarded it as one of their formidable military points. The capture of Chapultepec and the destruction of the post at Molino del Rey were, accordingly, determined on as preliminary to the final assault upon the city.
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As soon as the armistice was terminated bold reconnoissances were made by our engineers in the direction of Chapultepec and the Molino or King's Mill and Casa Mata. On the 7th of September Santa Anna's answer to Scott's despatch was received, and on the same day the Commander-in-Chief and General Worth examined the enemy's formidable dispositions near and around the castle-crowned hill. The Mexican array was found to consist of an extended line of cavalry and infantry, sustained by a field battery of four guns, either occupying directly or supporting a system of defences collateral to the castle and summit; but as the lines were skilfully masked a very inadequate idea of the extent of the forces was obtained. Captain Mason's reconnoissance on the morning of the same day, represented the enemy's left as resting on and occupying the group of strong stone buildings at the Molino adjacent to the grove at the foot of Chapultepec and directly under the castle's guns. The right of his line rested on the Casa Mata, at the foot of the ridge sloping gradually to the plain below from the heights above Tacubaya; while, midway between these buildings, were the field battery and infantry forces disposed on either side to support it. This reconnoissance indicated that the centre was the weak point of the position, and that its left flank was the strongest. In the Mill or Molino, on the left, was the brigade of General Leon, reinforced by the brigade of General Rangel; in the Casa Mata, on the right, was the brigade of General Perez; and on the intermediate ground was the brigade of General Ramirez, with several pieces of artillery. The Mexican reserve was composed of the 1st and 3d light, stationed in the groves of Chapultepec, while the cavalry consisting of 4,000 men, rested at the hacienda of Morales, not very far from the field. Such was the arrangement of the Mexican forces made by Santa Anna in person on the 7th of September, though it has been alleged by Mexican writers that it was somewhat changed during the following night. The wily chief had not allowed the time to pass during the negotiation between Trist and the Commissioners in political discussion alone. Regarding the failure of the treaty as most probable, he had striven to strengthen once more the military arm of his nation, and the first result of this effort was demonstrated in his disposition of troops at El Molino del Rey. The Americans' attack upon Chapultepec, as commanding the nearest and most important access to the city had been foreseen by him as soon as the armistice ended, and as a military man, he well knew that the isolated hill and castle could not be protected by the defenders within its walls alone or by troops stationed either immediately at its base or on the sloping road along its sides.