The first attack was by Hooker on the enemy's left, where he drove Jackson back, after he had been reinforced by Hood, cleared the woods, and took possession of the Dunker Church, which stood slightly north of Sharpsburg. A little way beyond the Confederates made a stand, and, being reinforced, recovered most of the ground they had lost. General Mansfield was killed and Hooker received a painful wound in the foot. When their two corps were retreating in confusion, Sumner arrived, rallied them, and made a successful stand. Seeing the critical situation, Lee hurried every available man to that point. This left only 2,500 troops in front of the bridge, where Burnside had 14,000. McClellan sent repeated orders for him to advance, but he paid no attention until one o'clock, when he crossed without trouble, and then remained idle for three more hours. The heights were soon captured, and a position secured from which the rebel lines could be enfiladed. A.P. Hill arrived at this juncture from Harper's Ferry with 4,000 men, and drove Burnside in a panic to the creek. Fighting soon ceased, both sides too much exhausted to keep up the terrific struggle, the position of the two armies being much the same as at first. This fierce battle had wrenched and disorganized both armies, but McClellan, who had much the larger body, could have destroyed or captured those in front of him, had he followed the urgent advice of his officers, and given the enemy no rest. But he decided to await reinforcements, which arrived to the number of 14,000 that night. Then he resumed his preparations, and on the morning of the 19th advanced against the enemy, only to find there was none in front of him. LEE'S RETREAT. The retreat of Lee was deliberate. Having accurately gauged the commander in front of him, he spent all of the 18th in completing his preparations, and made no move until the next morning. Then, protected by batteries on the opposite bank, he crossed the Potomac, and on the 20th drove back a Union reconnaissance. The government, impatient with McClellan's tardiness, urged and almost ordered him to follow up Lee, but the commander preferred to guard against being followed up himself by the Army of Northern Virginia. Thus again a golden opportunity slipped away unimproved. Naturally each side claimed a victory at Antietam or Sharpsburg, as it is called in the South, but such a claim in either case is hardly justifiable. It may be said, on the one hand, that Lee's invasion of the North was brought to a disastrous end by his check at Antietam, but the claim of Lee was that his failure to secure the expected recruits from Maryland, and his distance from the base of supplies, necessitated such a withdrawal on his part, for it is established that he was opposed to the northward advance from the first.