Civil War Campaigns
After decisively defeating the Union Army of Virginia under Maj. Gen. John Pope at Second Manassas (August 28-30) and fighting a drawn battle at Chantilly (September 1), Gen. Robert E. Lee followed his victory with an immediate attempt to invade the North. Lee's advance was one arm of a great Confederate offensive that extended along a 1,000-mile front from Tidewater, Virginia to the Indian Territory in the west.
On September 4, the Army of Northen Virginia crossed the Potomac River in an invasion of Union territory. The ragged Confederates, many of whom were barefoot, spilled into western Maryland, concentrating 3 days later at Frederick on the 9th. Lee proposed with this bold movement to relieve war-ravaged Virginia during the fall harvest. While at Frederick, formulated the details of his audacious campaign. In Special Order No. 191, Lee divided his army for the 3rd time in as many campaigns. Shielded by the South Mountain, Lee planned to move his army north into Pennsylvania. To open a supply line into the Shenandoah Valley, he sent Maj. Gen. Thomas J. Jackson against the Union garrison at Harper's Ferry. After capturing this force, Jackson was to reunite with Maj. gen. james Longstreet's 3 divisions for the thrust northward. Lee believed he could combine his divided command before his troops could be overtaken by the pursuing reunited Army of the Potomac.
Restored to full command in Virginia on September 2 by a doubting President Lincoln, Maj. Gen. George B. McClellan had reorganized his army. He advanced from Washington, D.C. on the 7th, the day the Confederates poured into Frederick. Uncertain of Lee's whereabouts or plans, covering the capital and Baltimore, the cautious McClellan marched slowly north-westward. For 5 days, the Union army filled the Maryland roads, its cavalry probing the horizen for the elusive Confederates. On the 10th, McClellan learned that the Confederates had abandoned Frederick, and the march quickened.
Two days later, the Union army entered Frederick, 48 hours behind the Confederates, and the next morning on the 13th, 2 Union infantrymen found a paper wrapped around 3 cigars. That paper, a copy of Lee's Special Order No. 191, was immediately forwarded through channels to McClellan. He suddenly possessed a great opportunity to destroy his divided opponent. McClellan, however, waited 16 hours before moving.
The Union army wrested control of the South Mountain passes, but on September 15, 12,000 Union soldiers at Harpers Ferry surrendered to Jackson, even as McClellan moved west to confront Lee at Sharpsburg.
At dawn on September 17, the Battle of Antietam, or Sharpsburg, began soon after dawn on a field shrouded in fog. The Union army launched a powerful assault on Lee's left flank that began the bloodiest day in American military history. McClellan's sound battle plan of assaults on both Confederate flanks soon faltered in a series of uncoordinated, piecemeal attacks. Hammering Union assaults were met with howling Confederate counterattacks. Artillerists on both sides scorched the field with shells and waves of canisters. Lee parried the thrusts by shifting troops from his right to the left and center. Maj. Gen. Ambrose E. Burnside's inexcusable failure to assault the Confederate right until afternoon permitted Lee to juggle his units. The arrival of Jackson's absent division finally saved the Confederate army when it repulsed Burnside's tardy assault. In a bloody war, the conflict's bloodiest day ended. Although outnumbered 2-to-1, Lee battled McClellan's army to a standstill.
In one day's fighting, the two armies suffered a combined total of more than 23,000 casualties (killed, wounded, missing, captured). In spite of crippling casualties, Lee continued to face McClellan throughout the 18th, while skirmishing. After dark, Lee ordered the battered Army of Northern Virginia to withdraw across the Potomac to the safety of the Shenandoah Valley. On the 20th, McClellan sent a force in pursuit, which Jackson repulsed. Lee's bold campaign ended without Maryland recruits or European recognition. A turning point had been reached. President Lincoln relieved McClellan of command.The Confederate cavalry continued to be active in the Shenandoah Valley. In order to gather supplies, Gens. Grumble Jones and John D. Imboden combined forces for raids into West Virginia.
Five days after the battle, on September 22, Lincoln issued the Emancipation Proclamation. The Union armies now had another goal, human freedom.