August 15. Headquarters left Ayotla at eleven, and proceeded to Chalco, Worth pushing from Chalco the same evening, and Quitman entering Chalco. Captain Lee and Lieutenant Tower were assigned to the brigade of Harney for temporary duty with the advance. The engineer company also joined the advance of Worth.
August 16. All the divisions in motion this morning. The road around the lakes was narrow and rough, in many cases passing through a narrow defile on the very edge of the lake, on one side abrupt acclivities, and on the other a quagmire, into which the least false step would plunge one several feet deep.
Headquarters, before reaching the camping-ground of Worth of the previous night, had to pass Quitman’s and Pillow’s train. On arriving at Chimalpa, headquarters remained some hours for authentic intelligence from Twiggs, it having been reported that in marching out from Ayotla, early in the morning, he had encountered a large force of the enemy under Alvarez. On learning that Taylor’s battery, in firing seven rounds, dispersed the large body of enemy’s lancers which made a demonstration against Twiggs at the point where the route left the national road to wind round Chalco, headquarters moved forward to Tulancingo, where we passed the night. This village is remarkable for its large and ancient olive groves. The olive-trees on either side of the road, stretching out their arms, form an arch above like the elms of New England.
August 17. Headquarters reached Xochimilco this day with Pillow’s and Quitman’s divisions, Worth advancing as far as San Augustin, and Twiggs reaching Pillow’s camping-ground of last evening. The road to-day was extremely difficult, and required some working to fill up cuts, and remove stones and other obstructions placed in the road. The march was very laborious in consequence of the continual halts.
Early on the morning of the 18th General Scott reached San Augustin, called the engineers, observed, “To-day the enemy may feel us, to-morrow we must feel him,” and ordered reconnoissances to determine the best mode of reaching the position of Tacubaya. There were two roads,—the direct by San Antonio, which was already ascertained to be occupied in strength by the enemy, and one to the west passing through Contreras and San Angel, known, however, for a portion of the distance to be simply a mule-path.
Major Smith directed in person the examination of the San Antonio route, assisted by Captain Mason, Lieutenants Stevens and Tower, and Captain Lee that to the west, assisted by Lieutenant Beauregard. The instructions of the general as to reconnoissances had been already anticipated by General Worth as regards the Contreras route, who had pushed his division forward, and dispatched Captain Mason, escorted by Thornton’s dragoons, to reconnoitre the enemy’s position at San Antonio. Whilst in the discharge of this duty two shots from a battery of the enemy were fired, killing Captain Thornton outright and severely wounding Fitzwater, an interpreter.
General Worth immediately placed his division in the occupancy of the Hacienda Cuapa, thus affording the most ample protection to the escorts of the engineers. Major Smith now ordered Captain Mason and Lieutenant Tower to examine the enemy’s right, and Lieutenant Stevens his left.
Captain Mason first went to the steeple of a church near by to determine the best mode of conducting his reconnoissance, and then with Colonel C.F. Smith’s light battalion he passed over a field of pedregal to our left, till he got a full view of the rear of the enemy. He traced paths leading to Mexicalcingo, interrogated the peons, and came to the conclusion that the whole position might be turned and the enemy made to abandon it, by crossing an infantry force on the line he had just pursued, and falling upon the enemy at daylight with the bayonet.
Lieutenant Stevens was twice recalled whilst pushing his reconnoissance, first, by order of Colonel Garland in consequence of an apprehended attack from the enemy, and second, by direction of Major Smith, the senior engineer. This officer did not deem it necessary to do anything further, observing to General Worth that he had examined the whole vicinity from the top of the hacienda, and had also interrogated the residents, and was satisfied that the ground was firm on our right, and afforded a route to turn the enemy’s position. Lieutenant Stevens expressed doubts as to this, and was permitted to go on with his examination. He persevered until night, and found that the ground was marshy, intersected with canals, and that operations in this direction were not practicable.
In the mean time Captain Lee, with Kearny’s dragoons and Graham’s 11th infantry, reconnoitred the route by Contreras. At about a mile and a half it became a mule-path, requiring to be worked to be practicable for artillery, and on ascending a hill a mile and a half farther on, a large intrenched camp opened to view at a mile’s distance, occupied in strength by the enemy, and completely closing the Contreras route, which for the intervening distance passed through a bed of pedregal, a lava rock of honeycomb projection. After passing the intrenched camp, the road was known to be good. At the hill the party had a successful skirmish with the enemy’s pickets, and then returned to San Augustin.