my[1] "When an enemy is in front of El Peñon, the communication between it and troops on the other routes is only by way of the city of Mexico itself; in other words, the American troops being at Ayotla, General Santa Anna's forces at El Peñon were one day's march distant from those at Mexicalzingo, three from those under General Valencia, and would have been about four days' march from troops thrown forward on the Chalco route. Fords on these different routes were by no means within supporting distances of each other. Holding the position that General Scott then did, it would have required, of an equal enemy, four times his own force, to have opposed successfully his further advance. The Mexican forces were not numerically equal to this, and, accordingly, they were concentrated at the threatened point. It is evident that as long as the American troops were in front of El Peñon, the enemy necessarily held to their position. In moving off, the former could gain one day the start. This brought the only difficult parts of the Chalco route actually nearer General Scott than the Mexican chief. If to this we add the delay necessary in moving heavy artillery and breaking up from a fortified position, it would seem that, instead of oversight, it was rather impossible for General Santa Anna to meet our forces sooner than he did."
The description of the various routes to the capital has necessarily acquainted the reader with the important Mexican defences on the north, the east, and the north-east of the capital, both by military works hastily thrown up after Santa Anna's retreat from Cerro Gordo, and by the encampment of large bodies of soldiery. We thus, already know a part of the external line of defences at El Peñon, Mexicalzingo, Tezcoco, Santiago Zacualco, and the Pass north of Tenepantla. But in addition to these, there are others that must be noticed on the south and west of the capital, which it should always be recollected is situated in the lap of the valley, but near the western edge of the gigantic rim of mountains.
Along the Chalco route there were no more fortifications, but west of lakes Chalco and Xochimilco, a line of entrenchments had been commenced, connecting the fortified hacienda, or massive stone plantation house of San Antonio, about six miles south of the city, with the town of Mexicalzingo. West of this hacienda, the Pedregal, a vast, broken field of lava, spread out along the edge of the
- ↑ See the admirable Map and Memoir of Lieutenant M. L. Smith, and Brevet Captain E. L. F. Hardcastle, published in the Senate Document, No. 11 of the first session of the 31st Congress: 1849 '50.
