He assigned them to attack certain areas but failed to communicate an overall plan or to coordinate their assaults.
Despite advice from his corps commanders to withdraw during the night of the 17th, Lee said Mc Clellan would not attack the next day and remained in place until withdrawing on the night of the 18th.
Such Union pursuit as there was ended in a sharp skirmish just south of the Potomac at Shepherdstown, in what is now West Virginia.
Believing the routed Union army would require time to rebuild, Lee took the bold step of dividing his own army, sending portions of it to capture various objectives.
Primarily, these objectives involved using part of Lieutenant General Thomas "Stonewall" Jackson’s corps to capture the Union garrison at Harpers Ferry, Virginia (now West Virginia), while the largest corps, that of Lt. James Longstreet, proceeded on the road toward Sharpsburg. Mc Clellan, who had been recalled from the Virginia peninsula along with the Army of the Potomac (see Seven Days Battle).
Lying on the downside of the slope and rolling onto their sides to reload, they poured fire into the ranks of the Confederates below, who responded in kind. Anderson himself was wounded soon after arriving on the field and, except for Wright’s brigade, his 3,000–4,000 men provided little help to Hill, whose men were finally pushed out by weight of numbers.
Blood turned the dirt in the road to mud, giving the sunken road the sobriquet Bloody Lane. At the extreme right of Lee’s line, three Confederate batteries and the 600-man infantry brigade of Brig. Robert Toombs looked down from a steep hill onto Rohrbach Bridge, a narrow, stone bridge over Antietam Creek on the Rohrersville–Sharpsburg Road.Rocky outcroppings throughout the battlefield caused solid-shot shells to ricochet wildly. The oldest general officer in Mc Clellan’s army, the 59-year-old Mansfield was mortally wounded while riding forward to reconnoiter and was replaced by Brig. Reinforcements that might have carried the day for the Union at that point never arrived, and another Federal drive stalled. French’s division swung to the left, toward the center of the Confederate line. A sheet of flame erupted from the sunken road and the crest of the ridge was covered with a blue blanket of dead or wounded Union soldiers.For a time, the Union troops made progress, but attack and counterattack turned the West Woods and Miller’s cornfield into slaughter pens. Major General Edwin Sumner’s II Corps crossed Antietam Creek sometime after a.m., with orders to support the two corps already engaged. John Sedgewick followed part of the XII Corps toward the West Woods, while Brig. Under fire from sharpshooters and artillery, the first of French’s brigades crested a little rise; less than 100 yards below them in a sunken farm road were three Confederate brigades of Maj. The brigade fell back; another took its place, with the same result.Instead, fearing Lee might outnumber him, he moved his men to the ridges east of Antietam Creek, where he paused to let them rest. "Jeb" Stuart’s cavalry guarding the gap between the Potomac and the infantry’s left flank.By midday of September 16, all but three of Lee’s nine divisions had arrived. Although a strong position with the advantage of interior lines of communication, it might also be a death trap with the Potomac cutting off retreat.The overcast, drizzly morning of September 17 soon gave way to sunshine that glinted off the bayonets and rifle barrels of Hooker’s men as they marched toward a whitewashed Church of the Baptist Brethren, a sect commonly called Dunkers because they practiced complete immersion in baptisms.