It was about noon of the 15th of September that Lee placed the forces which he had in hand across the turnpike in front of Sharpsburg. D. H. Hill's division was on the north of the road, and on the south of it Longstreet's own old division (now under General D. R. Jones), Hood's division, and Evans's independent brigade. Stuart's cavalry and the reserve artillery were also present. The rest of the army was with Jackson at Harper's Ferry, or co-operating with him in the neighborhood of Maryland Heights. Out of forty-four brigades, Lee could put but fourteen or fifteen in line that day to oppose McClellan. He was very strong in artillery, however, and his cannon looked grimly over the hill-crests behind which his infantry were lying. Cutts's and Jones's battalions of the reserve artillery were ordered to report to Hill for the protection of the left of the Confederate line, and gave him in all the sixty or seventy guns which he speaks of in his report, and which have puzzled several writers who have described the battle. Whenever our troops showed themselves as they marched into position, they were saluted from shotted cannon, and the numerous batteries that were developed on the long line of hills before us no doubt did much to impress McClellan with the belief that he had the great bulk of Lee's army before him.
The value of time was one of the things McClellan never understood. He should have been among the first in the saddle at every step in the campaign after he was in possession of Lee's order of the 9th, and should have infused energy into every unit in his army. Instead of making his reconnoissance at three in the afternoon of Monday, it might have been made at ten in the morning, and the battle could have been fought before night, if, indeed, Lee had not promptly retreated when support from Jackson would thus have become impossible. Or if McClellan had pushed boldly for the bridge at the mouth of the Antietam, nothing but a precipitate retreat by Lee could have prevented the interposition of the whole National army between the separated wings of the Confederates. The opportunity was still supremely favorable for McClellan, but prompt decision was not easy for him. Nothing but reconnoitring was done on Monday afternoon or on Tuesday, whilst Lee was straining every nerve to concentrate his forces and to correct what would have proven a fatal blunder in scattering them, had his opponent acted with vigor. The strongest defence the eulogists of the Confederate general have made for him is that he perfectly understood McClellan's caution and calculated with confidence upon it; that he would have been at liberty to perfect his combinations still more at leisure, but for the accident by which the copy of his plan had fallen into our hands at Frederick City.
During the 16th we confidently expected a battle, and I kept with my division. In the afternoon I saw General Burnside, and learned from him that McClellan had determined to let Hooker make a movement on our extreme right to turn Lee's position. Burnside's manner in speaking of this implied that he thought it was done at Hooker's solicitation, and through his desire, openly evinced, to be independent in command. I urged Burnside to assume the immediate command of the corps and allow me to lead my own division. He objected that as he had been announced as commander of the right wing of the army, composed of the two corps, he was unwilling to waive his precedence or to assume that Hooker was detached for anything more than a temporary purpose. I pointed out that Reno's staff had been granted leave of absence to take the body of their chief to Washington, and that my division staff was too small for corps duty; but he met this by saying that he would use his staff for this purpose, and help me in every way he could till the crisis of the campaign should be over. Sympathizing with his very natural feeling, I ceased objecting, and accepted with as good grace as I could the unsatisfactory position of nominal commander of the corps to which I was a comparative stranger, and which, under the circumstances, naturally looked to him as its accustomed and real commander. Burnside's intentions in respect to myself were thoroughly friendly, as he afterward proved, and I had no ground for complaint on this score; but the position of second in command is always an awkward and anomalous one, and such I felt it.
The 16th passed without serious fighting, though we had desultory cannonading and picket firing. It was hard to restrain our men from showing themselves on the crest of the long ridge in front of us, and whenever they did so they drew the fire from some of the enemy's batteries, to which ours would respond. McClellan reconnoitred the line of the Antietam near us, and the country immediately on our left, down the valley. As the result of this we were ordered to change our positions at nightfall, staff officers being sent to guide each division to its new camp. The selected positions were marked by McClellan's engineers, who then took members of Burnside's staff to identify the locations, and these in turn conducted our divisions. There was far more routine of this sort in that army than I ever saw elsewhere. Corps and division commanders should have the responsibility of protecting their own flanks and in choosing ordinary camps. To depend upon the general staff for this is to take away the vigor and spontaneity of the subordinate and make him perform his duty in a mechanical way. He should be told what is known of the enemy and his movements so as to be put upon his guard, and should then have freedom of judgment as to details. The changes made were as follows: Rodman's division went half a mile further to the left, where a country road led to the Antietam ford, half a mile below the Burnside bridge. Sturgis's division was placed on the sides of the road leading to the stone bridge just mentioned. Willcox's was put in reserve in rear of Sturgis. My own was divided, Scammon's brigade going with Rodman, and Crook's going with Sturgis. Crook was ordered to take the advance in crossing the bridge in case we should be ordered to attack. This selection was made by Burnside himself as a compliment to the division for the vigor of its assault at South Mountain. While we were moving we heard Hooker's guns far off on the right and front, and the cannonade continued an hour or more after it became dark.
What, then, was the plan of battle of which the first step was this movement of Hooker's? McClellan's dispositions on the 15th were made whilst Franklin's corps was still absent, and, under the orders he received, was likely to be so for a day at least. [Footnote: Official Records, vol. xix. pt. i. p. 29.] Sumner's two corps had been treated as the centre of the army in hand, Burnside's had been divided by putting Hooker on the extreme right and the Ninth Corps on the extreme left, and Porter's corps was in reserve. This looked as if a general attack in front with this organization of the army were intended. But the more McClellan examined the enemy's position the less inclined he was to attack the centre. He could cross the bridge there and on the right, and deploy; but the gentle slopes rising toward Sharpsburg were swept by formidable batteries and offered no cover to advancing troops. The enemy's infantry was behind stone fences and in sunken roads, whilst ours must advance over the open. Lee's right rested upon the wooded bluffs above the Burnside bridge, where it could only be approached by a small head of column charging along the narrow roadway under a concentrated fire of cannon and small arms. No point of attack on the whole field was so unpromising as this. Then, as Jackson was still at Harper's Ferry, there was the contingency of an attack in rear if anything less than the mass of our army were pushed beyond Lee's right.
On our right, in front of Hooker, it was easy to turn the Confederate line. The road from Keedysville through Smoketown to the Hagerstown turnpike crossed the Antietam in a hollow, out of the line of fire, and a march around Lee's left flank could be made almost wholly under cover. The topography of the field therefore suggested a flank attack from our right, if the National commander rejected the better strategy of interposing his army between Lee and Jackson as too daring a movement. This flank attack McClellan determined to make, and some time after noon of the 16th issued his orders accordingly. In his preliminary report of the battle, made before he was relieved from command, McClellan says:--
"The design was to make the main attack upon the enemy's left,--at least to create a diversion in favor of the main attack, with the hope of something more, by assailing the enemy's right,--and as soon as one or both of the flank movements were fully successful, to attack their centre with any reserve I might then have in hand." [Footnote: O R., vol. xix. pt. i. p. 30.]
His report covering his whole career in the war, dated August 4, 1863 (and published February, 1864, after warm controversies had arisen, and he had become a political character), modifies the above statement in some important particulars. It says:--
"My plan for the impending general engagement was to attack the enemy's left with the corps of Hooker and Mansfield supported by Sumner's and if necessary by Franklin's, and as soon as matters looked favorably there, to move the corps of Burnside against the enemy's extreme right upon the ridge running to the south and rear of Sharpsburg, and having carried their position to press along the crest toward our right, and whenever either of these flank movements should be successful, to advance our centre with all the forces then disposable." [Footnote: Official Records, vol. xix, pt. i, p. 55.]
The opinion I got from Burnside at the time, as to the part the Ninth Corps was to take, was fairly consistent with the design first quoted, namely, that when the attack by Sumner, Hooker, and Franklin should be progressing favorably, we were "to create a diversion in favor of the main attack, with the hope of something more." It is also probable that Hooker's movement was at first intended to be made by his corps alone, the attack to be taken up by Sumner's two corps as soon as Hooker began, and to be shared in by Franklin if he reached the field in time, thus making a simultaneous oblique attack from our right by the whole army except Porter's corps, which was in reserve, and the Ninth Corps, which was to create the "diversion" on our left and prevent the enemy from stripping his right to reinforce his left. It is hardly disputable that this would have been a better plan than the one actually carried out. Certainly the assumption that the Ninth Corps could cross the Antietam alone at the only place on the field where the Confederates had their line immediately upon the stream which must be crossed under fire by two narrow heads of column, and could then turn to the right along the high ground occupied by the hostile army before that army had been broken or seriously shaken elsewhere, is one which would hardly be made till time had dimmed the remembrance of the actual position of Lee's divisions upon the field. It is also noticeable that the plan as given in the final report leaves no "centre" with which to "advance" when either of the flank movements should be successful, Porter's corps in reserve being the only one not included in the movement as described.