As General Robert E. Lee’s Army of Northern Virginia advanced into Maryland in the fall of 1862, Lee made plans to capture the vital Union garrison at Harpers Ferry in the rear of his invading army. Although Maj. Gen. George McClellan's Army of the Potomac was in pursuit, in a bold maneuver Lee divided his army, sending three columns under Gen. Thomas “Stonewall” Jackson to Harpers Ferry while the rest of the army marched towards Hagerstown, Maryland. Surrounded on three sides by steep heights, the terrain at Harpers Ferry made it nearly impossible to defend, a problem made worse by the Union commander, Colonel Dixon S. Miles, who lacked experience leading troops. For three days, Jackson’s troops placed artillery on the heights looking down on Harpers Ferry, and on the morning of September 15th, Jackson ordered an artillery barrage that bombarded the small yet strategic town, followed by an infantry assault by Maj. Gen. A. P. Hill's division at 8 a.m. Miles, believing the situation to be hopeless, decided to surrender the garrison and its more than 12,000 men. As the decision to surrender was debated, Miles was struck by a shell that shattered his left leg, a wound that proved fatal. Jackson took possession of Harpers Ferry before joining the rest of Lee’s army at Sharpsburg, leaving Hill’s division at the garrison to process the parole of prisoners.