CHAPTER XIII. 1847.

Santa Anna and his engineers had probably supposed that this southern route would not be adopted, but a reasonable explanation of his conduct is given by one of the most competent commentators upon the valley of Mexico and the march of the American army. "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