During the night of the 11th batteries were established which could play upon the fortifications of Chapultepec.  The bombardment commenced early on the morning of the 12th, but there was no further engagement during this day than that of the artillery.  General Scott assigned the capture of Chapultepec to General Pillow, but did not leave the details to his judgment.  Two assaulting columns, two hundred and fifty men each, composed of volunteers for the occasion, were formed.  They were commanded by Captains McKinzie and Casey respectively.  The assault was successful, but bloody.

In later years, if not at the time, the battles of Molino del Rey and Chapultepec have seemed to me to have been wholly unnecessary.  When the assaults upon the garitas of San Cosme and Belen were determined upon, the road running east to the former gate could have been reached easily, without an engagement, by moving along south of the Mills until west of them sufficiently far to be out of range, thence north to the road above mentioned; or, if desirable to keep the two attacking columns nearer together, the troops could have been turned east so as to come on the aqueduct road out of range of the guns from Chapultepec.  In like manner, the troops designated to act against Belen could have kept east of Chapultepec, out of range, and come on to the aqueduct, also out of range of Chapultepec.  Molino del Rey and Chapultepec would both have been necessarily evacuated if this course had been pursued, for they would have been turned.

General Quitman, a volunteer from the State of Mississippi, who stood well with the army both as a soldier and as a man, commanded the column acting against Belen.  General Worth commanded the column against San Cosme.  When Chapultepec fell the advance commenced along the two aqueduct roads.  I was on the road to San Cosme, and witnessed most that took place on that route.  When opposition was encountered our troops sheltered themselves by keeping under the arches supporting the aqueduct, advancing an arch at a time.  We encountered no serious obstruction until within gun-shot of the point where the road we were on intersects that running east to the city, the point where the aqueduct turns at a right angle.  I have described the defences of this position before.  There were but three commissioned officers besides myself, that I can now call to mind, with the advance when the above position was reached.  One of these officers was a Lieutenant Semmes, of the Marine Corps.  I think Captain Gore, and Lieutenant Judah, of the 4th infantry, were the others.  Our progress was stopped for the time by the single piece of artillery at the angle of the roads and the infantry occupying the house-tops back from it.