Maryland campaign  

As Jackson's three columns approached Harpers Ferry, Col. Dixon S. Miles, Union commander of the garrison, insisted on keeping most of the troops near the town instead of taking up commanding positions on the surrounding heights. The South Carolinians under Brig. Gen. Joseph B. Kershaw encountered the slim defenses of the most important position, Maryland Heights, but only brief skirmishing ensued. Strong attacks by the brigades of Kershaw and William Barksdale on September 13 drove the mostly inexperienced Union troops from the heights.[39]

During the fighting on Maryland Heights, the other Confederate columns arrived and were astonished to see that critical positions to the west and south of town were not defended. Jackson methodically positioned his artillery around Harpers Ferry and ordered Maj. Gen. A.P. Hill to move down the west bank of the Shenandoah River in preparation for a flank attack on the Federal left the next morning. By the morning of September 15, Jackson had positioned nearly 50 guns on Maryland Heights and at the base of Loudoun Heights. He began a fierce artillery barrage from all sides and ordered an infantry assault. Miles realized that the situation was hopeless and agreed with his subordinates to raise the white flag of surrender. Before he could surrender personally, he was mortally wounded by an artillery shell and died the next day. Jackson took possession of Harpers Ferry and more than 12,000 Union prisoners, then led most of his men to join Lee at Sharpsburg, leaving Maj. Gen. A.P. Hill's division to complete the occupation of the town.[40]

South Mountain[edit]

Further information: Battle of South Mountain and Battle of Crampton's Gap

Pitched battles were fought on September 14 for possession of the South Mountain passes: Crampton's, Turner's, and Fox's Gaps. Maj. Gen. D.H. Hill defended Turner's and Fox's Gaps against Burnside. To the south, Maj. Gen. Lafayette McLaws defended Crampton's Gap against Franklin, who was able to break through at Crampton's Gap, but the Confederates were able to hold Turner's and Fox's, if only precariously. (For the counter argument that the Union held Fox's Gap, see Older, Curtis L., Hood's Defeat Near Fox's Gap September 14, 1862.)[41] Lee realized the futility of his position against the numerically superior Union forces, and he ordered his troops to Sharpsburg. McClellan was then theoretically in a position to destroy Lee's army before it could concentrate. McClellan's limited activity on September 15 after his victory at South Mountain, however, condemned the garrison at Harpers Ferry to capture and gave Lee time to unite his scattered divisions at Sharpsburg.[42]

Antietam (Sharpsburg)

On September 16, McClellan confronted Lee near Sharpsburg. Lee was defending a line to the west of Antietam Creek. At dawn on September 17, Maj. Gen. Joseph Hooker's I Corps mounted a powerful assault on Lee's left flank that began the bloody battle. Attacks and counterattacks swept across the Miller Cornfield and the woods near the Dunker Church as Maj. Gen. Joseph K. Mansfield's XII Corps joined to reinforce Hooker. Union assaults against the Sunken Road ("Bloody Lane") by Maj. Gen. Edwin V. Sumner's II Corps eventually pierced the Confederate center, but the Federal advantage was not pressed. In the afternoon, Burnside's IX Corps crossed a stone bridge over Antietam Creek and rolled up the Confederate right. At a crucial moment, A.P. Hill's division arrived from Harpers Ferry and counterattacked, driving back Burnside's men and saving Lee's army from destruction. Although outnumbered two to one, Lee committed his entire force, while McClellan sent in only four of his six available corps. This enabled Lee to shift brigades across the battlefield and counter each individual Union assault. During the night, both armies consolidated their lines. In spite of crippling casualties—Union 12,401, or 25%; Confederate 10,316, or 31%—Lee continued to skirmish with McClellan throughout September 18, while transporting his wounded men south of the Potomac. McClellan did not renew the offensive. After dark, Lee ordered the battered Army of Northern Virginia to withdraw across the Potomac into the Shenandoah Valley.[43]

Shepherdstown[edit]

Further information: Battle of Shepherdstown

On September 19, a detachment of Maj. Gen. Fitz John Porter's V Corps pushed across the river at Boteler's Ford, attacked the Confederate rear guard commanded by Brig. Gen. William N. Pendleton, and captured four guns. Early on September 20, Porter pushed elements of two divisions across the Potomac to establish a bridgehead. A.P. Hill's division counterattacked while many of the Federals were crossing and nearly annihilated the 118th Pennsylvania (the "Corn Exchange" Regiment), inflicting 269 casualties. This rearguard action discouraged further Federal pursuit.[44]

Aftermath and diplomatic implications[edit]

Lee successfully withdrew across the Potomac, ending the Maryland campaign and summer campaigning altogether. President Lincoln was disappointed in McClellan's performance. He believed that the general's cautious and poorly coordinated actions in the field had forced the battle to a draw rather than a crippling Confederate defeat. He was even more astonished that from September 17 to October 26, despite repeated entreaties from the War Department and the president, McClellan declined to pursue Lee across the Potomac, citing shortages of equipment and the fear of overextending his forces. General-in-Chief Henry W. Halleck wrote in his official report, "The long inactivity of so large an army in the face of a defeated foe, and during the most favorable season for rapid movements and a vigorous campaign, was a matter of great disappointment and regret."[45] Lincoln relieved McClellan of his command of the Army of the Potomac on November 7, effectively ending the general's military career. Maj. Gen. Ambrose E. Burnside rose to command the Army of the Potomac. The Eastern Theater was relatively quiet until December, when Lee faced Burnside at the Battle of Fredericksburg.[46]

Although a tactical draw, the Battle of Antietam was a strategic victory for the Union. It forced the end of Lee's strategic invasion of the North and gave Abraham Lincoln the victory he was awaiting before announcing the Emancipation Proclamation on September 22, which took effect on January 1, 1863. Although Lincoln had intended to do so earlier, he was advised by his Cabinet to make this announcement after a Union victory to avoid the perception that it was issued out of desperation. The Confederate reversal at Antietam also dissuaded the governments of France and Great Britain from recognizing the Confederacy. And, with the issuance of the Emancipation Proclamation, it became less likely that future battlefield victories would induce foreign recognition. Lincoln had effectively highlighted slavery as a tenet of the Confederate States of America, and the abhorrence of slavery in France and Great Britain would not allow for intervention on behalf of the South.[47]

The Union lost 28,272 men during the Maryland campaign (2,783 killed, 12,108 wounded, 13,381 missing).