THE VALLEY OF MEXICO
CHAPTER X
ADVANCE TO MEXICO, EL PEÑON, CONTRERAS, CHURUBUSCO
The City of Mexico is situated in the centre of an irregular basin some thirty-five miles from north to south and twenty-five miles from east to west, and is separated from the great plain of Puebla by the eastern branch of the great Cordillera of Anahuac, interposing an elevation of nineteen hundred feet at the Pass of the Rio Frio.
It was known from information collected by the engineers that the city was entirely surrounded either by an inundation or by marshy ground, and was approached by eight causeways, flanked with wet ditches, and provided with numerous cuts; that the whole city was protected by a double and in some quarters by a triple line of defensive works, well armed with cannon, and defended by an army of some thirty thousand men. The direct approach along the great national road was defended by the strong position of the Peñon, seven miles from the city. Chapultepec stood boldly out on the southwest, and on the north there were said to be formidable works at Guadalupe.
After entering the valley along the national road, there were three general modes of approaching the city,—the direct along the national road, around Lake Tezcuco on the north, Chalco and Xochimilco on the south.
All the information collected pointed to the south and west as the proper quarter from whence to attack the city; the south presented an extended front with four of the eight causeways of entrance nearly parallel to each other, and was necessarily weak. On the west the suburb of San Cosme, a single street lined with houses on either side, extended well into the country, and afforded a vulnerable point. Chapultepec, not deemed a very formidable obstacle, required to be swept away to be free to select the point of attack. Hence Tacubaya, a strong village overawing Chapultepec, became the key point of the whole operation. In the particular operation against the southern front, the occupancy of the church and village of Piedad was of the last importance, in view of all the southern gates, communicating directly with all the villages in rear from Tacubaya to San Augustine, and by a good cross road controlling the three causeways of San Antonio, Nino Perdido, and Piedad.
Before ultimately deciding upon the strategic line, General Scott determined to enter the valley at the head of the column, and whilst the rear was closing up, to employ spies and push forward reconnoissances to get accurate information of all the material facts bearing on the plan of operations.
Accordingly, on the 7th of August the division of Twiggs, with the engineer company at its head, led the advance, followed on successive days by Quitman, Worth, and Pillow. General Scott and staff joined the advance on the 8th. On the 11th Twiggs reached Ayotla, fifteen miles from Mexico, Quitman Buena Vista, Worth Rio Frio, Pillow Tesmaluca, respectively 3½ miles, 11½ miles, and 20½ miles in rear.