In a few weeks another Federal threat confronted Lee. Gen. John Pope moved overland from Washington with a newly formed army. His target was also Richmond. Lee shifted his army northward to block the advance. On August 9 Jackson checked Pope’s lead elements at Cedar Run, a few miles south of Culpeper. Then, while Pope warily eyed Lee’s main force, Jackson’s men swept around the Federal right flank and captured Pope’s all-important supply base at Manassas. An angry Pope turned around and started in pursuit of Jackson.
Pope soon found Jackson. But Gen. James Longstreet, commanding the other half of Lee’s army, found Pope. The August 28-30 campaign of Second Manassas—or Second Bull Run—resulted. As in the first battle in that area, the Federals met defeat. Pope managed to check a thrust by Lee at Chantilly (September 1), then retired to Washington.
Virginia was now clear of Federal forces. The time was ripe, Lee thought, to invade the North. Success might secure Maryland for the Confederacy and bring official recognition to the Southern nation from England and France. Then both foreign powers would send supplies, and possibly troops, to aid the Southern cause.
Lee’s grayclad regiments waded across the Potomac River on September 5, 1862. At Frederick, Md., Lee divided his army. Jackson marched southward to capture Harpers Ferry and keep the Valley avenue open, while Lee proceeded westward to Sharpsburg.
Harpers Ferry first gained prominence in history with John Brown’s 1859 raid. During the Civil War it was a key point in Eastern military operations.
Meanwhile, Lincoln assigned what was left of Pope’s force to McClellan and sent “Little Mac” in pursuit of the Confederate invaders. On September 14 McClellan fought his way through the passes of South Mountain, Maryland. The next day, as McClellan’s troops converged on Lee, Jackson seized Harpers Ferry. Jackson then hastened northward and rejoined Lee at Sharpsburg late on September 16.
Wednesday, September 17, produced the largest one-day bloodbath on American soil. From sunrise until dusk Federal units made repeated assaults on Lee’s lines. Had McClellan thrown his entire army against Lee’s position, the weight of numbers probably would have destroyed the Army of Northern Virginia. Instead, the Federal commander shifted his attacks from one sector to another. Casualties mounted frightfully in such areas as the East Wood, West Wood, Dunker Church, Sunken Road, and around Burnside’s Bridge. By nightfall Lee’s battered army still held its position. McClellan had lost 12,000 men, the Confederates 9,000.
The battle of Antietam Creek ended Lee’s invasion, and he retired to Virginia. Five days after the engagement, Lincoln issued his preliminary Emancipation Proclamation. This document promised freedom to all slaves in Confederate-held territory after January 1, 1863. As such, it converted the war into a struggle for human freedom and deterred European nations from granting aid or recognition to the Confederacy. Many historians therefore maintain that Antietam Creek and its aftermath were the turning points of the Civil War.
For six weeks after Antietam, McClellan seemed to make little effort to resume the campaign against Lee. Lincoln tired of waiting; on November 5 he replaced McClellan with Gen. Ambrose E. Burnside.