The Battle of Shepherdstown, also known as the Battle of Boteler's Ford, took place September 19–20, 1862, at Boteler's Ford along the Potomac River, during the Maryland campaign of the American Civil War. After the Battle of Antietam on September 17, General Robert E. Lee and the Confederate Army of Northern Virginia withdrew across the Potomac. Lee left a rear guard commanded by Brigadier General William N. Pendleton at Boteler's Ford. On September 19, elements of the Union V Corps dueled with Pendleton's artillery before pushing a short distance across the river at dusk. Pendleton inaccurately informed Lee that all of the artillery of the rear guard had been captured. On the morning of September 20, the Confederates counterattacked with A. P. Hill's Light Division, forcing the Union units back across the Potomac. One Union unit, the 118th Pennsylvania Infantry Regiment, did not withdraw at the same time as the others and suffered heavy losses. Lee's army continued its retreat into the Shenandoah Valley after the battle. Background In June 1862, during the American Civil War, General Robert E. Lee took command of the Confederate Army of Northern Virginia after the wounding of General Joseph E. Johnston at the Battle of Seven Pines. Lee's army faced the Union Army of the Potomac, which was led by Major General George B. McClellan. In the Seven Days Battles, Lee's army drove McClellan and the Army of the Potomac back from its position close to the Confederate capital of Richmond, Virginia. Lee then faced a Union advance by Major General John Pope's Army of Virginia, coming from a different direction. Lee's army defeated Pope at the Second Battle of Manassas in late August. Despite having suffered heavy casualties in the previous two campaigns, Lee led his army on an invasion of the Union, striking into the state of Maryland. McClellan replaced Pope as commander of the Union forces, and took the Army of the Potomac north after Lee. Some of McClellan's soldiers discovered Lee's military orders, revealing the Confederate plans on McClellan. On September 14, McClellan forced Lee's army back from the passes on South Mountain; and both armies gathered around Sharpsburg, Maryland, where McClellan attacked on September 17. In the resulting Battle of Antietam, Lee's outnumbered army repulsed Union assaults throughout the day. Nearly 23,000 men were killed, wounded, or became missing in action during the fighting, making Antietam the bloodiest day