WASHINGTON, August 29, 1862, 4.10 P. M. Yours of to-day just received. I think your first alternative, to-wit.: "to concentrate all our available forces to open communication with Pope," is the right one, but I wish not to control. That I now leave to Gen. Halleck, aided by your counsels. A. LINCOLN.

Maj.-Gen. MCCLELLAN,

After the battle of the 30th, and the opening of free communication for the enemy at Thoroughfare Gap, through which the main army of Lee was now pouring in great numbers, it only remained for Gen. Pope to withdraw his army, as best he could, toward Washington. All the troops were withdrawn to Centreville in good order, where they were rested during the day, on the 31st, receiving supplies and ammunition. Here he was joined by Sumner and Franklin, with an aggregate reenforcement of 19,000 men. On the 1st of September, the enemy was found moving toward Fairfax Court House, endangering Pope's right. Due precautions had been taken, so that when the right was attacked at sunset, the enemy was met by McDowell, Reno, Hooker, and Kearney. A sharp conflict followed, at Chantilly, in the midst of a thunder-storm, terminating soon after dark. The Rebels were handsomely repulsed. Maj. Gen. Kearney and Brig.-Gen. Stevens were among our

killed.

On the 2d, the forces under Gen. Pope were ordered to be withdrawn within the intrenchments around Washington, which movement was executed in good order. Directly after, Gen. Pope was relieved, and appointed to the command of the Department of the Northwest.

Gen. McClellan, on the 1st of September, was orally directed by Gen. Halleck to take command of the defenses of Washington. He immediately entered on the work, his command, however, being still limited to the Army of the Potomac, and no new jurisdiction being assigned to him outside of the fortifications. It was without any formal extension of this authority that he went out to meet the enemy in Maryland, where Lee next assumed a threatening position, having gone out by Lees burg and crossed the Upper Potomac.

Proceeding cautiously, until the purpose of the enemy was definitely developed, the advance of Gen. McClellan's forces, on the 14th of September, came up with and defeated the rearguard of Lee at South Mountain. This was a gallant action, in which Gen. Burnside and his corps took a conspicuous part, and in which Gen. Reno lost his life. On the side of the Government, about 30,000 men were engaged, at various points, including the forces under Gen. Meade. The Commanding General reports his losses as 312 killed, 1,234 wounded, and 22 missing. About 1,500 prisoners were taken from the enemy, whose losses in killed and wounded were estimated to have largely excceded those of the Government forces.

Meanwhile, Gen. Franklin had been executing a movement on the left, by Crampton's Gap, where he had a sharp engagement. He was directed to relieve Harper's Ferry, where Col. Miles, with a force of nearly 14,000 men, was in imminent danger. Before Franklin came to his aid, though within sound of his guns, Miles (who was soon after killed) had surrendered his position, his munitions of war, and his entire force of infantry and artillery. His cavalry, numbering about 2,000, cut its way out on the night of the 14th, under the command of Col. Davis, capturing, on its route to the Government lines, the train of Longstreet and over one hundred prisoners.

McClellan's forces were soon through the mountain passes, and a prompt engagement with the enemy was expected, with a view to prevent his return across the Potomac, without a erushing defeat. The circumstances now seemed favorable to this result, the forces of McClellan being massed in the immediate vicinity of the Rebel army, which was now contending merely for a secure retreat-in itself a concession of decided inferiority.

On the 15th, the enemy made a stand on the hights beyond Antietam Creek, in the vicinity of Sharpsburg. McClellan, seeing the formidable position thus occupied, deemed it advisable to prepare with great deliberation, for the attack he had intended to make at once. The 15th and most of the 16th were accordingly employed in this preparation, during which time

the enemy also made new dispositions, some artillery firing going on during both days. Meanwhile, Jackson's forces returned from the capture of Harper's Ferry. The corps of Sumner and Hooker (the latter of whom had taken the place of Heintzelman, assigned to duty within the fortifications at Washington) were posted on the right, near Keedyville, on both sides of the Sharpsburg turnpike. Franklin's corps and Couch's division were placed in front of Brownsville, in Pleasant Valley. Burnside's corps occupied a position on the left. Heavy artillery was massed in the center, behind which, in the low ground, Porter's corps was held in reserve. The right, center and left, were each, respectively, near three stone bridges across Antietam Creek, the one on the right being about three and a half miles from that on the left.

In the evening of the 16th, Hooker's corps advanced across the stream, by the upper bridge and by a ford near it, with orders to endeavor to turn the enemy's left. After a short engagement, the opposing force was driven back, and Hooker encamped for the night on the ground thus gained. Sumner's corps crossed at the same point, and was followed by the corps of Gen. Mansfield (the Twelfth, consisting of the divisions of Gens. Williams and Green.)

At an early hour on the morning of the 17th, Hooker made an attack on the enemy's left-his whole corps being soon engaged, as well as the remaining troops that had crossed over, on the right. Franklin's corps and other forces were also brought into action. The contest was a severe one, the enemy having evidently moved a heavy force to the support of his left his right not having been engaged by Burnside, until after the heaviest of this fighting was over. Gen. Mansfield fell mortally wounded. Gen. Hooker was early so severely wounded as to be compelled to leave the field. Gen. Hartsuff, of Hooker's corps, was also badly wounded, as were Gens. Sedgwick and Dana, and many other officers. On both sides, there was heavy slaughter. The enemy was finally driven backward some distance, and our right held the position gained.

Gen. Burnside's advance, on the left, was not commenced until hours after Hooker had brought on the action on the

right. About 8 o'clock in the morning, he was ordered by the Commanding General to carry the bridge before him, and to occupy the hights beyond, advancing along their summit. toward Sharpsburg. The bridge was not carried until 1 o'clock, and a halt was again made until 3, the hights being finally carried in a gallant manner. Burnside earnestly asked, but failed to receive reënforcements from the heavy reserve under Porter, which remained inactive through the day. The enemy, as night approached, heavily reënforced his right, compelling Burnside to fall back to a lower range of hills than that he had gained.

On the whole, our forces had gained a substantial advantage, and had inflicted the heaviest damage on the enemy, in killed and wounded.

Instead of renewing the engagement, next morning, as a less prudent general would undoubtedly have done, Gen. McClellan spent the 18th "in collecting the dispersed, giving rest to the fatigued, removing the wounded, burying the dead, and the necessary preparations for a renewal of the battle." During the night of the 18th, Lee's entire army retreated across the Potomac. "As their line was but a short distance from the river," Gen. McClellan says in his final report, "the evacuation presented but little difficulty, and was effected before daylight." His dispatches of the 19th, show that he regarded these matters somewhat differently at the time. In fact, several hours elapsed, before the Commanding General appears to have understood how completely the enemy had eluded his grasp.

In his official dispatch of Sept. 29, Gen. McClellan says, in summing up his estimate of the Rebel losses:

As nearly as can be determined at this time, the number of prisoners taken by our troops in the two battles will, at the lowest estimate, amount to 5,000. The full returns will no doubt show a larger number. Of these about 1,200 are wounded. This gives the Rebel loss in killed, wounded and prisoners, 25,542. It will be observed that this does not include their stragglers, the number of whom is said by citizens here to be large. It may be safely concluded, therefore, that the Rebel army lost at least 30,000 of their best troops during their campaign in Maryland.

In his last report, Gen. McClellan states his own losses during the same period as amounting, in the aggregate, to 15,520.

It was not until the 20th, that Maryland Hights were occupied by the corps of Gen. Williams. On the 22d, Gen. Sumner was advanced to Harper's Ferry. On the 23d, Gen. McClellan regarded the enemy as still remaining in front of him, with "indications of an advance of reënforcements," and accordingly proceeded to act on a defensive policy. On the 27th, he believes "the main body of the enemy is concentrated not far from Martinsburg," and extending "toward our right and beyond it." All efforts to induce a vigorous pursuit of an enemy lately represented as completely routed and panicstricken, proved of no avail.

On the 1st of October, the President visited the army, (the headquarters of which were still on the Maryland side of the Potomac) and passed over the battle-fields of South Mountain and Antietam, in company with Gen. McClellan. It is not too much to say that this visit was made, in part, from the extreme anxiety felt by Mr. Lincoln on account of the protracted delay in moving the army, and from a desire to ascertain, by personal observation, how far this inaction was necessary or reasonable. On the President's return, the following dispatch was sent by Gen. Halleck to Gen. McClellan :

WASHINGTON, D. C., October 6, 1862. I am instructed to telegraph you as follows: The President directs that you cross the Potomac and give battle to the enemy, or drive him south. Your army must move now, while the roads are good. If you cross the river between the enemy and Washington, and cover the latter by your operation, you can be reënforced with thirty thousand men. If you move up the valley of the Shenandoah, not more than twelve or fifteen thousand can be sent you. The President advises the interior line between Washington and the enemy, but does not order it. He is very desirous that your army move as soon as possible. You will immediately report what line you adopt, and when you intend to cross the river; also to what point the rëenforcements are to be sent. It is necessary that the plan of your operations be positively determined on, before orders are given for building bridges and repairing railroads. I am directed to add, that the Secretary of War and the General-in-chief fully concur with the President in these instructions.