The peculiar geography of Mexico City creates a unique problem for attackers. In those days the city was situated on slightly elevated ground and was surrounded by swampy, marshy fields. The only approach to the city was via straight narrow causeways that were raised. Not unlike some of the terrain in France that had to be traveled by attacking infantry in the invasion of Normandy. AN Advance along any of the them put troops into a perfect position to be shot down like ducks in a row. It also put them into the sights of the cross fire from the city gates.

The US Army was situated so that the most direct approach to the city was along the thee causeways that ran to the city from south to north. The two that approached the city from the southwest and west were dominated by a steep 220 foot tall hill less than 2 miles from the HQ of Commanding General Winfield Scott.

The hill was topped by a “neo romantic” castle that had been transformed into Mexican Military Academy. The road to the top was zigzagging trip up a sheer cliff surrounded at its base by a high stone wall. Chapultepec looked like major obstacle the Mexicans would be certain to defend fiercely due to its symbolic significance.

Lee had proven to be a talented recon scout and engineer with a talented eye for terrain and where to place and sight in artillery for General Scott up to this point in the Mexican Campaign and he put his talents to work finding the best way to attack Mexico City.

Lee was sent to find the best way to attack Mexico City from the south. Setting out with two other engineers, Lee managed to get ” within a mile and a quarter of the city” and observed what the Mexicans were doing to improve and strengthen the defenses. Lee was impressed and became uncharacteristically cautious about the possibility of assaulting Chapultepec. However, he was convinced that the city could be taken by a well coordinated attacks from the south.

Lee spent September 9-11ths in continuous recon missions with no rest, looking for the best place to place artillery. In any case on the 11th Scott decided to assault Chapultepec instead, convinced that a well conducted artillery barrage would drive the Mexican soldiers out of the fortress and when it fell, the city would be open from an attack from it’s summit. With American artillery placed on it the hill would dominate the two western approaches to the city only a mile away.

Lee gave every effort to prepare for the attack on Chapultepec for the next 48 hours. He placed four batteries of heavy artillery , working so furious that the first two batteries were able to open fire on the morning of September the 12th, less than 24 hours after Lee received his orders. This was a major feat. Extreme labor and danger were involved in bringing 8 inch howitzers and 16 and 24 pounder guns across the soft marshy ground and sitting them in platforms that had to be dug by hand with the pick and shovel all in full view of the enemy defenders and under constant enemy fire.

Once the guns were in place Lee moved ahead to examine the approaches to Chapultepec more closely.

Lee returned to the commanding General’s HQ to find Scott was in a rage at not knowing the effect of the artillery on the defenses of the fortress. Scott was determined to attack that evening and had ordered one division to the west through the dense cypress grove at the foot of Chapultepec, and another to attack from the south, directly up the steep road cut into the cliff face.

Volunteers had been formed into two “storming parties” equipped with scaling ladders to lead the assault. It fell to Lee to as the senior engineer officer present and the one who had been closest to the objective ,to brief the commanders who would carry out the attack. During the night the troops moved into their positions west and south of Chapultepec, while others made an ostentatious demonstration in view of the southern gate, hoping to fix Santa Anna’s attention in the wrong direction.

Lee spent the nigh inspecting and double checking the artillery batters and making sure that damaged caused by the Mexican return fire was quickly repaired. By this point Lee had gone 48 hours without sleep, but his orders were to guide General Pillow’s division in its attack on the western face of Chapultepec. He set out with the lead parties as soon as the artillery ceased a 80 on the morning on September 13, exposed to artillery fire, musket fire and the rare use of land mines at the time.

Lee watched while the scaling ladders were brought forward and as the storming parties were pushed back with heavy casualties. He regrouped the troops and hit success with the second attempt. Lee then himself climbed the steep slope to the terraces at the top, accompanied by Lt. James Longstreet, who would go on to be one of his corps commanders in the CSA.

At some point in the attack Lee was wounded, but managed to help the wounded division commander Pillow back to safety, then climbed the summit in time to see the American flag raised. The fortress turned out to not be much of a fortress at all. Having been built as a palace, it didn’t offer much protection to the Mexican defenders inside. The huge building was then taken room by room by the US troops while American troops ran “wild looting and hunting down the now defenseless Mexicans in retaliation for the atrocities of Molino del Rey.” Lee being one of the officers restoring order to the troops.

Lee watched the US troops raise the Stars and Stripes over Chapultepec replacing the Mexican flag. At the same time the US flag was raised, 50 captured soldiers of the St. Patrick Battalion of deserters who had been condemned to death were hanged. battle.

“Thirty of them were hanged in full view of the battle , each of them standing in the back of a mule drawn cart, hands tied behind them, the noose already fastened to the immensely long crosspiece of a huge mass gallows built for the purpose on a low hilltop facing the fortress. At the moment the US flag was raised above a cloud of black smoke…teamsters whipped the mules. and the deserters dropped to their death amid the sound of cheering from their former comrades“

It had an effect on the defenders of Mexico City which Lee instantly recognized instantly. With the victory, organized Mexican resistance collapsed. Lee by then was exhausted and had yet to have his wound dressed, made his way back to General Scott to report the overwhelming success of the attack, and then made another reconnaissance of the ground leading toward the Sane Cosme gate at the northwestern corner of the city. When returning again to report to General Scott, he then fainted from exhaustion for the first and only time of his life. He had been on his feet, in the saddle and in combat for three days and nights without sleep or rest.

When Lee awakened before dawn, Lee Learned that US troops had already entered the city and captured the citadel while Santa Anna had fled. Lee entered the city at first light and was watching in the grand plaza as “General Scott rode in about eight in the morning in full dress uniform to see the American flag raised over the National Palace. After this Scott reviewed the troops as they presented arms, then dismounted, doffed his plumed hat and entered the palace”

For the next two days American troops had to fight in street battles with criminals turned loose by Santa Anna from the prisons before he fled. This fighting would be the last Lee saw until 1861.

For Lee’s part in the battle Lee was promoted to brevet colonel. This would be the highest rank he held until 1861. Most importantly Lee had an chance to learn the art of generalship from under the command of an expert, who very much valued and trusted him at a level far above his rank. “Lee had learned the value of reconnaissance and he had learned the value of audacity in warfare and the bold flank attack as well as the possibilities of advancing swiftly beyond the conventional lines of communication and living off the land.” Later he relied on these lessons learned from his experience in Mexico.

Lee returned home 22 months after leaving for Mexico. During that time he earned a reputation throughout the army. In the words of General Scott ” the very best soldier that I ever saw in the field”.

In 13 more years, many Union commanders would learn just how skilled Lee was.