"Do all you can to annoy the rebels should they advance on you...You will not abandon Harpers Ferry without defending it to the last extremity."
Maj. Gen. John G. Wool, USA
Telegraph message to Col. Dixon S. Miles, USA
September 7, 1862
The first large-scale Federal occupation of Harpers Ferry began in February 1862. Despite the destruction of the armory and arsenal the previous year, Harpers Ferry remained important in protecting Union communication and supply lines and in deterring Confederate invasions of the North.
The Confederates invaded the North for the first time in September 1862. By September 7, Gen. Robert E. Lee's army had crossed the Potomac River and encamped outside Frederick, Maryland. The large Union force at Harpers Ferry, now located behind the invading Confederates, threatened Southern communication and supply lines. In response, Lee boldly divided his army into four parts, sending three columns to capture or destroy the Union garrison at Harpers Ferry.