Harper's Ferry, were for a time interpreted as evidences of the enemy's disorganization and demoralization.
As soon as it was definitely know that the enemy had abandoned the mountains, the cavalry and the corps of Sumner, Hooker, and Mansfield were ordered to pursue them, via the turnpike and Boonsborough, as promptly as possible. The corps of Burnside and Porter (the latter having but one weak division present) were ordered to move by the old Sharpsburg road, and Franklin to advance into Pleasant Valey, occupy Rohrersville, and to endeavor to relieve Harper's Ferry. Burnside and Porter, upon reaching the road from Boonsborough to Rohrersville, were to re-enforce Franklin or to move on Sharpsburg, according to circumstances. Franklin moved toward Brownsville and found there a force, largely superior in numbers to his own, drawn up in a strong position to receive him. Here the total cessation of firing in the direction of Harper's Ferry indicated but too clearly the shameful and premature surrender of that post.
The cavalry advance overtook a body of the enemy's cavalry in Boonsborough, which it dispersed after a brief skirmish, killing and wounding many, taking some 250 prisoners and 2 guns.
Richardson's division, of Sumner's corps, passing Boonsborough to Centreville or Keedysville, found a few miles beyond the town the enemy's forces displayed in line of battle, strong both in respect to numbers and position, and awaiting attack. Upon receiving reports of the disposition of the enemy, I directed all the corps, except that of Franklin, upon Sharpsburg, leaving Franklin to observe and check the enemy in his front and avail himself of any chance that might offer. I had hoped to come up with the enemy during the 15th in sufficient force to beat them again and drive them into the river. My instructions were that if the enemy were on the march they were to be at once attacked; if they were found in force and in position, the corps were to be placed in position for attack, but no attack was to be made until I reached the front.
On arriving at the front in the afternoon I found but two divisions Richardson's and Sykes'-in position. The rest were halted in the road, the head of the column some distance in rear of Richardson. After a rapid examination of the position, I found that it was too late to attack that day, and at once directed locations to be selected for our batteries of position, and indicated the bivouacs for the different corps, massing them near and on both sides of the Sharpsburg pike. The corps were not all in their places until the next morning some time after sunrise.
On the 16th the enemy had slightly changed their line, and were posted upon the heights in rear of the Antietam Creek, their left and center being upon and in front of the road from Sharpsburg to Hagerstown, and protected by woods and irregularities of the ground. Their extreme left rested upon a wooded eminence near the cross-roads, to the north of J. Miller's farm, the distance at this point between the road and the Potomac, which makes here a great bend to the east, being about three-fourths of a mile. Their right rested on the hills to the right of Sharpsburg, near Snavely's farm, covering the crossing of the Antietam and the approaches to the town from the southeast. The ground between their immediate front and the Antietam is undulating. Hills intervene, whose crests in general are commanded by the crests of others in their rear. On all favorable points their artillery was posted. It became evident from the force of the enemy and the strength of their