William Starr Myers, ed. The Mexican War Diary of George B. McClellan. (Princeton: 1917), pages 79-88.

          ...Suddenly a turn of the road displayed Plan del Rio at our feet-the little valley filled with troops, horses, artillery, wagons, etc. We arrived at about
          10:30 A.M.-found the Engineers and took a lunch with them. G. W. S[mith] and myself then rode out to Twiggs's position with Captain Lee-we arrived
          just in time to see the ball open [i.e., the battle of Cerro Gordo]. Saw old Twiggs, who wondered "Where the devil did you two boys come from?" and
          started back to bring up the company. On the way back a round shot came about as near my head as would be regarded agreeable in civil life and then
          missed enfilading the 2nd Infantry about a foot and a half. When we got back to El Plan, I was ordered to join Tower with ten men-to go with Gid
          Pillow and the Mohawks. Did my best that afternoon to find out where we were to go in the morning but none of them would tell me anything about it.
          G. W. left me ten of the best men in the company, and took Foster and the rest with him to report to General Twiggs. It seemed to be a mutual thought
          that the chances all were that we would not meet again! The idea of being killed by or among a parcel of Volunteers was anything but pleasant.

          Got up before daybreak-woke up the men-had the mare fed and saddled-drank some coffee-distributed tools to my party and was ready for battle
          long before our dear Mohawks had their breakfasts. Also gave some tools to the Volunteers. My men had hatchets, axes and billhooks-the Volunteers
          [had] axes, sap-forks and billhooks. At length all was ready and much to my surprise we marched straight up the road toward Jalapa. So little did I
          know of our point of attack-I only knew that we were to attack either their right or front, and that we would as surely be whipped-for it was a
          Volunteer Brigade. I led off with my detachment, and after passing the greater part of Worth's Division-which was formed in column of platoons in the
          road-we turned off to the left, nearly opposite the point where Twiggs turned to the right. Tower directed me to place my men on the path inclining most
          to the left. I did so and rested my men, whilst waiting for the Volunteers who were a long distance behind. At length General Pillow came up, and seeing
          my men, directed that they should be placed on the path inclining to the right.

          Lieutenant Tower made some remark about changing the route, and also that we would be more apt to be seen when crossing some ravine if we went
          to the right. I remember distinctly that the impression made upon my be the conversation was that General Pillow had against the opinion of Lieutenant
          Tower changed the route to be followed in order to attain the point of attack. I had no idea of the importance of the change and that it could lead to a
          different point of attack. I afterward found that the different paths led to very different parts of the enemy's position, the one we actually followed
          bringing us in a very exposed manner against the front of the works, whilst if we had taken the one advised by Lieutenant Tower we should have turned
          the right of their works and have been but little exposed to their fire.

          The fault of the erroneous selection was General Pillow's, except that Lieutenant Tower should, as the senior Engineer with the column, have taken a
          firm stand and have forced General Pillow to have pursued the proper path. It was certainly a fine opportunity for him to show what stuff he was made
          of-but unfortunately he did not take advantage of it at all.

          We at length moved off by the flank. My detachment [was] at the head, and during the movement-at all events before the firing against us
          commenced-we heard the musketry of the attack of Twiggs's Division upon the Telegraph Hill.

          After moving about two-thirds of a mile from the main road we reached a certain crest bordering upon a ravine, whence a strong picket of Mexicans
          was observed. Tower advised General Pillow to incline his Brigade well to the right in order to cross the ravine lower down and out of view. The
          General directed Colonel Wynkoop to countermarch-file twice to the right and move upon a certain dead tree as his point of direction (Colonel
          Campbell's Tennessee Regiment to support him). He was then to form his men for the attack and charge upon hearing a concerted signal from the rest
          of the Brigade. Colonel Haskell at once commenced forming his Regiment in a column of platoon, the flank of the column toward the work. His men
          having straggled a great deal this arrangement was attended with some difficulty-the men being literally shoved into their places one by one. Hardly two
          platoons were formed when General Pillow shouted out at the top of his voice-"Why the H-l dont Colonel Wynkoop file to the right?" I may here
          observe that we had heard very distinctly the commands of the Mexican officers in their works. This yell of the General's was at once followed by the
          blast of a Mexican bugle and within three minutes after that their fire opened upon us. The General may have shouted this before a single platoon of
          Haskell's was formed-but the interval must have been very short, because Wynkoop's Regiment had not reached its destination and had not formed
          there when the firing commenced.

          When the Mexican fire opened Haskell's Regiment became at once "confusion worse confounded." Some of the men rushed toward the works, many
          broke to the rear, very many immediately took cover behind the rocks, etc. I at once asked General Pillow for orders to proceed "somewhere" with my
          detachment-for I had as yet received no orders or directions from anyone and was utterly ignorant of the ground. While talking with the General-who
          was squatting down with his back to the work-he was wounded in the arm, upon which his aide, Lieutenant Rains, appeared from somewhere in the
          vicinity and they together went off to the rear, on the run. I then went in amongst the Tennesseeans and found at once that it was useless to attempt
          doing anything there, as that Regiment (Haskell's) was utterly broken and dispersed and the Pennsylvania Regiment, which was to support them, had
          kept so well in reserve that they could not be found. I then went over to the other side of the ravine-the firing had by this time nearly if not altogether
          ceased.

          Upon arriving there I found Campbell's Regiment in pretty good order and in good spirits, the Pennsylvania Regiment (Wynkoop's) in most horrible
          confusion. Campbell was moving on toward the work, and I at once advised General Pillow to halt him until some order could be restored to the other
          Regiments. He took my advice and directed me to give the order to Campbell, which I did. I thought that it was by no means certain that Campbell
          alone could carry the works and that if he were checked or repulsed all was lost, for there was not a company formed to support him. Besides, although
          his Regiment was moving on well, they were not then under fire, nor had they been under any fire, to speak of, that day-so I doubted the steadiness of
          their movements when their advance should have brought them in sight and under the fire of, the Mexicans.

          Colonel Haskell came up without his cap about this time and a very warm conversation ensued between him and General Pillow-the General accusing
          him of misconduct and deserting his troops, the Colonel repelling his assertions and stating that his Regiment was cut to pieces. I at once, without saying
          a word to either the General or the Colonel, called to my party and directed them to beat the bushes for "2nd Tennesseeans" and to bring all they could
          find to where we were. They soon returned with quite a number.

          In the course of conversation I told General Pillow that I did not think that he could carry the works without some Regulars. He assented and directed
          me to go at once in search of General Scott and ask him, from him (Pillow) for a detachment of Regulars-whatever number he could spare, saying that
          he would make no movement until my return. I immediately ran down to the road where I expected to find General Scott and Worth's Division and
          there found that the General had gone on. I jumped on my mare and galloped around by Twiggs's road and at length found the General about half way
          up the ridge over which Worth's Division passed to reach the Jalapa road-the rear of Worth's Division was then crossing. I told the General my
          message and he directed me to say to General Pillow that he had no Regulars to spare, that the last of Worth's Division was then passing over, that
          Santa Anna had fallen back with all his army, except about 5000 men, toward Jalapa, that he expected to fight another battle with Santa Anna at once,
          and that he thought it probable that the 5000 men cut off would surrender-finally that General pillow might attack again, or not, just as he pleased. He
          evidently was not much surprised and not much "put out" that Pillow was thrashed, and attached no importance to his future movements.

          With this reply I returned, and could not for a long time, find any of the valiant Brigade. I at length found Wynkoop's Regiment. He told me that white
          flags were flying on the work and that one or two had come down toward his position-but that as he did not know what they meant, could not raise a
          white handkerchief in the crowd, and had no one who could speak Spanish, he had held no communication with them. I told him what they meant and
          said that when I had seen General Pillow I would return and go to meet them. As I left he asked me if I could not give him an order to charge-I said
          "No"-then said he-"Tell General Pillow that if I don't get an order to charge in half an hour, I'll de d-d if I dont charge anyhow"-this after I had told him
          that the white flag meant a surrender!!!

          I at length found General Pillow some distance in rear and reported. Castor came up a moment or two afterward and told General Pillow that he had
          been sent to inform him that the Mexicans had surrendered-on which I took my men down the road and directing them to come on and rejoin the
          company as soon as possible-I galloped on to overtake it. During my conversation with General Scott he mentioned that he had seen the charge of
          Twiggs's Division and spoke of it as the most beautiful sight that he had ever witnessed. He said everything in praise of his "rascally Regulars."

          With reference to the operations of Twiggs's Division.-During the afternoon of the 17th [April] the hill opposite to and commanded by the Telegraph Hill
          was carried by Harney's (Smith's) Brigade and the enemy pursued partly up the Telegraph Hill by the Rifles and 1st Artillery. They were, however,
          recalled to the hill first mentioned, which was occupied in force.