Life of Franklin Pierce by Nathaniel Hawthorne

General Scott, who was at Puebla with the main army awaiting this reenforcement, began his march towards the city of Mexico on the day after General Pierce's arrival. The battle of Contreras was fought on the 19th of August.

The enemy's force consisted of about seven thousand men, posted in a strongly-intrenched camp, under General Valencia, one of the bravest and ablest of the Mexican commanders. The object of the commanding general appears to have been to cut off the communications of these detached troops with Santa Anna's main army, and thus to have them entirely at his mercy. For this purpose a portion of the American forces were ordered to move against Valencia's left flank, and, by occupying strong positions in the villages and on the roads towards the city, to prevent reenforcements from reaching him. In the mean time, to draw the enemy's attention from this movement, a vigorous onset was made upon his front; and as the operations upon his flank were not immediately and fully carried out according to the plan, this front demonstration assumed the character of a fierce and desperate attack, upon which the fortunes of the day much depended. General Pierce's brigade formed a part of the force engaged in this latter movement, in which four thousand newly-recruited men, unable to bring their artillery to bear, contended against seven thousand disciplined soldiers, protected by intrenchments, and showering round shot and shells against the assailing troops.