Union Col. Francis Barlow saw the gap in the Confederate front opened by Rodes’ withdrawal. Quickly swinging two regiments astride the road, he raked its length with perfectly timed volleys. Routed by this devastating enfilade, the Confederate defenders fled the road and retreated south toward Sharpsburg. Only a heroic rally by D. H. Hill’s men prevented a breakthrough into the town. The Sunken Road was now Bloody Lane. Dead Confederates lay so thick there, wrote one Federal soldier, that as far down the road as he could see, a man could have walked upon them without once touching ground. [Illustration: _On the Firing Line._ By Gilbert Gaul. Courtesy, Library of Congress.] [Illustration: _Bloody Lane._ Courtesy, Library of Congress.] The Federals had suffered heavily, too. Their bodies covered the approaches to the ridge. In the final moments, while leading his men in pursuit, Colonel Barlow had been seriously wounded; and shortly after, his commander, General Richardson, had fallen with a mortal wound. The fight for the Sunken Road had exhausted both sides. At 1 p.m. they halted, and panting men grabbed their canteens to swish the dust and powder from their rasping throats. The Confederate retreat from Bloody Lane had uncovered a great gap in the center of Lee’s line. A final plunge through this hole would sever the Confederate army into two parts that could be destroyed in detail. “Only a few scattered handfuls of Harvey Hill’s division were left,” wrote Gen. William Allen, “and R. H. Anderson’s was hopelessly confused and broken.... There was no body of Confederate infantry in this part of the field that could have resisted a serious advance.” So desperate was the situation that General Longstreet himself held horses for his staff while they served two cannon supporting Hill’s thin line. But McClellan’s caution stopped the breakthrough before it was born. Though Franklin’s VI Corps was massed for attack, McClellan restrained it. “It would not be prudent to make the attack,” he told Franklin after a brief examination of the situation, “our position on the right being ... considerably in advance of what it had been in the morning.” So McClellan turned to defensive measures. Franklin’s reserve corps would not be committed, but would remain in support of the Federal right. And in the center, McClellan held back Fitz-John Porter’s V Corps. After all, reasoned the Federal commander, was not this the only force that stood between the enemy and the Federal supply train on the Boonsboro Pike?