But Porter was not quite alone. The entire Federal artillery reserve stood with him. Further, Brig. Gen. Alfred Pleasonton had placed his cavalry and artillery on a commanding ridge west of the Middle Bridge during the morning. From here he had already supported the attack by Sumner’s corps on the Sunken Road, and he had aided Burnside’s efforts on the left. Now he stood poised for further action. Pleasonton was to wait in vain. His dual purpose of obtaining “... an enfilading fire upon the enemy in front of Burnside, and of enabling Sumner to advance to Sharpsburg” was nullified by McClellan’s decision to halt and take the defensive. In striking contrast to McClellan’s caution, General Lee was at that very moment considering a complete envelopment of the Federal flank at the North and East Woods. By this means he might relieve the pressure on D. H. Hill; for despite the lull, Lee could not believe that McClellan had halted the attack there. If the attack in the North Woods succeeded, Lee hoped to drive the Federal remnants to the banks of Antietam Creek and administer a crushing defeat. Jackson and J. E. B. Stuart, early in the afternoon, shifted northward and prepared to charge the Federal lines. When they arrived close to the powerful Federal artillery on Poffenberger Ridge, they saw that a Confederate attack there would be shattered by these massed guns. A wholesome respect for Federal artillerists now forced Lee to withdraw his order. As he did so, heavy firing to the south heralded a new threat developing there. _Burnside Takes the Lower Bridge_ During the morning of the 17th, Confederate observers on the ridge north of Sharpsburg had spotted masses of Federals moving southward beyond Antietam Creek. These were the four divisions of Burnside’s IX Corps concentrating for the attack on the Lower Bridge. Topography at the Lower Bridge heavily favored the few hundred Georgia men who defended it under the leadership of Brig. Gen. Robert Toombs. The road approaching the east end of the bridge swings on a course paralleling that of Antietam Creek; in the last few hundred yards before reaching the bridge, the road plunges into a funnel-like depression between the opposing bluffs of the creek. Toombs’ men were in rifle pits on the west bluff overlooking the bridge and the approach road. Because of faulty reconnaissance, Burnside did not know that fords were nearby where his men could have waded across the stream. Instead, the Federal plan of attack forced the advancing columns to pile into this funnel and storm across the bridge. Soon after 9 a.m., the Federal divisions began to assault the bridge. One after another, their gallant charges were broken by deadly short-range fire from Toombs’ Georgians. By noon, when the agony at the Sunken Road was reaching its highest pitch, and despite repeated orders from McClellan to get across Antietam Creek at all costs, the bottleneck at the bridge was still unbroken.