The village of Harpers Ferry lies at the gateway cut through the mountains by the Potomac and Shenandoah Rivers, whose waters join there. Situated at the apex of the triangle of land between the rivers, the town is completely dominated by Loudoun and Maryland Heights. By nightfall of September 14, McLaws and Walker had artillery on these heights ready for plunging fire into the town; Jackson had stretched his lines across the base of the triangle between the rivers.

Caught in this trap were nearly 12,000 Federal troops commanded by Col. D. S. Miles. Their position was indefensible.

At daybreak on September 15, the surrounding Confederate artillery opened fire. At 8 a.m., the hopelessness of his position confirmed, Miles ordered the surrender; he was killed in the last moments of the battle.

Jackson immediately sent word of his victory to Lee. Then, after assigning Maj. Gen. A. P. Hill’s division to dispose of prisoners and booty, he prepared the rest of his troops for the hard march ahead.

The same dawn that signaled Jackson’s guns to open fire on Harpers Ferry revealed Longstreet’s tired soldiers taking position on the rolling hills around Sharpsburg. As he watched them, Lee still did not know whether to fight or to withdraw across the Potomac. Decision waited upon word from Jackson. The word came; it was good; the crisis was past. Even now Lee’s messenger hurried to direct Jackson’s veterans toward Sharpsburg. Confident that the entire army would soon be at hand, certain that he could whip McClellan, Lee decided to fight.