The brigade to which I was attached — Garland's, of Worth's division — was sent to confront San Antonio, two or three miles from St. Augustin Tlalpam, on the road to Churubusco and the City of Mexico. The ground on which San Antonio stands is completely in the valley, and the surface of the land is only a little above the level of the lakes, and, except to the south-west, it was cut up by deep ditches filled with water. To the south-west is the Pedregal — the volcanic rock before spoken of — over which cavalry or artillery could not be passed, and infantry would make but poor progress if confronted by an enemy. From the position occupied by Garland's brigade, therefore, no movement could be made against the defences of San Antonio except to the front, and by a narrow causeway, over perfectly level ground, every inch of which was commanded by the enemy's artillery and infantry. If Contreras, some three miles west and south, should fall into our hands, troops from there could move to the right flank of all the positions held by the enemy between us and the city. Under these circumstances General Scott directed the holding of the front of the enemy without making an attack until further orders.
On the 18th of August, the day of reaching San Augustin Tlalpam, Garland's brigade secured a position within easy range of the advanced intrenchments of San Antonio, but where his troops were protected by an artificial embankment that had been thrown up for some other purpose than defense. General Scott at once set his engineers reconnoitring the works about Contreras, and on the 19th movements were commenced to get troops into positions from which an assault could be made upon the force occupying that place. The Pedregal on the north and north-east, and the mountain on the south, made the passage by either flank of the enemy's defences difficult, for their work stood exactly between those natural bulwarks; but a road was completed during the day and night of the 19th, and troops were got to the north and west of the enemy.
This affair, like that of Cerro Gordo, was an engagement in which the officers of the engineer corps won special distinction. In fact, in both cases, tasks which seemed difficult at first sight were made easier for the troops that had to execute them than they would have been on an ordinary field. The very strength of each of these positions was, by the skill of the engineers, converted into a defence for the assaulting parties while securing their positions for final attack. All the troops with General Scott in the valley of Mexico, except a part of the division of General Quitman at San Augustin Tlalpam and the brigade of Garland (Worth's division) at San Antonio, were engaged at the battle of Contreras, or were on their way, in obedience to the orders of their chief, to reinforce those who were engaged. The assault was made on the morning of the 20th, and in less than half an hour from the sound of the advance the position was in our hands, with many prisoners and large quantities of ordnance and other stores. The brigade commanded by General Riley was from its position the most conspicuous in the final assault, but all did well, volunteers and regulars.
From the point occupied by Garland's brigade we could see the progress made at Contreras and the movement of troops toward the flank and rear of the enemy opposing us. The Mexicans all the way back to the city could see the same thing, and their conduct showed plainly that they did not enjoy the sight. We moved out at once, and found them gone from our immediate front. Clarke's brigade of Worth's division now moved west over the point of the Pedregal, and after having passed to the north sufficiently to clear San Antonio, turned east and got on the causeway leading to Churubusco and the City of Mexico. When he approached Churubusco his left, under Colonel Hoffman, attacked a tete-de-pont at that place and brought on an engagement. About an hour after, Garland was ordered to advance directly along the causeway, and got up in time to take part in the engagement. San Antonio was found evacuated, the evacuation having probably taken place immediately upon the enemy seeing the stars and stripes waving over Contreras.
The troops that had been engaged at Contreras, and even then on their way to that battle-field, were moved by a causeway west of, and parallel to the one by way of San Antonio and Churubusco. It was expected by the commanding general that these troops would move north sufficiently far to flank the enemy out of his position at Churubusco, before turning east to reach the San Antonio road, but they did not succeed in this, and Churubusco proved to be about the severest battle fought in the valley of Mexico. General Scott coming upon the battle-field about this juncture, ordered two brigades, under Shields, to move north and turn the right of the enemy. This Shields did, but not without hard fighting and heavy loss. The enemy finally gave way, leaving in our hands prisoners, artillery and small arms. The balance of the causeway held by the enemy, up to the very gates of the city, fell in like manner. I recollect at this place that some of the gunners who had stood their ground, were deserters from General Taylor's army on the Rio Grande.
Both the strategy and tactics displayed by General Scott in these various engagements of the 20th of August, 1847, were faultless as I look upon them now, after the lapse of so many years. As before stated, the work of the engineer officers who made the reconnoissances and led the different commands to their destinations, was so perfect that the chief was able to give his orders to his various subordinates with all the precision he could use on an ordinary march. I mean, up to the points from which the attack was to commence. After that point is reached the enemy often induces a change of orders not before contemplated. The enemy outside the city outnumbered our soldiery quite three to one, but they had become so demoralized by the succession of defeats this day, that the City of Mexico could have been entered without much further bloodshed. In fact, Captain Philip Kearney — afterwards a general in the war of the rebellion — rode with a squadron of cavalry to the very gates of the city, and would no doubt have entered with his little force, only at that point he was badly wounded, as were several of his officers. He had not heard the call for a halt.
General Franklin Pierce had joined the army in Mexico, at Puebla, a short time before the advance upon the capital commenced. He had consequently not been in any of the engagements of the war up to the battle of Contreras. By an unfortunate fall of his horse on the afternoon of the 19th he was painfully injured. The next day, when his brigade, with the other troops engaged on the same field, was ordered against the flank and rear of the enemy guarding the different points of the road from San Augustin Tlalpam to the city, General Pierce attempted to accompany them. He was not sufficiently recovered to do so, and fainted. This circumstance gave rise to exceedingly unfair and unjust criticisms of him when he became a candidate for the Presidency. Whatever General Pierce's qualifications may have been for the Presidency, he was a gentleman and a man of courage. I was not a supporter of him politically, but I knew him more intimately than I did any other of the volunteer generals.
General Scott abstained from entering the city at this time, because Mr. Nicholas P. Trist, the commissioner on the part of the United States to negotiate a treaty of peace with Mexico, was with the army, and either he or General Scott thought — probably both of them — that a treaty would be more possible while the Mexican government was in possession of the capital than if it was scattered and the capital in the hands of an invader. Be this as it may, we did not enter at that time. The army took up positions along the slopes of the mountains south of the city, as far west as Tacubaya. Negotiations were at once entered into with Santa Anna, who was then practically the government and the immediate commander of all the troops engaged in defence of the country. A truce was signed which denied to either party the right to strengthen its position, or to receive reinforcements during the continuance of the armistices, but authorized General Scott to draw supplies for his army from the city in the meantime.
Negotiations were commenced at once and were kept up vigorously between Mr. Trist and the commissioners appointed on the part of Mexico, until the 2d of September. At that time Mr. Trist handed in his ultimatum. Texas was to be given up absolutely by Mexico, and New Mexico and California ceded to the United States for a stipulated sum to be afterwards determined. I do not suppose