The Maryland Campaign of 1862 — Robert E. Lee's First Invasion of the North

September 4–September 20, 1862

The Maryland Campaign (1862) — also known as the Antietam Campaign — was Robert E. Lee's First Invasion of the North, during the Civil War. The campaign failed, Lee returned South, and President Lincoln issued the Preliminary Emancipation Proclamation. The campaign included the Battle of Antietam, the bloodiest day of fighting in the war.

Robert E Lee, 1864, Portrait

General Robert E. Lee, Confederate States of America. Image Source: Wikipedia.

Maryland Campaign Summary

The Maryland Campaign of 1862 was Confederate General Robert E. Lee’s first invasion of the North. Lee was motivated by the need for supplies and the chance to reduce Northern support for the war. Lee divided his army, but Union soldiers found a copy of his plans, and General George B. McClellan advanced to prevent the Confederate army from reuniting. The Union victory at the Battle of South Mountain gave McClellan a chance to crush Lee’s army. However, McClellan failed to take advantage and the Maryland Campaign continued.

The Confederate victory at the Battle of Harpers Ferry convinced Lee to stand and fight. However, it led to the Battle of Antietam — the bloodiest single day of battle in the Civil War. Although the battle ended as a tactical draw, it was a strategic Union victory. Lee’s advance halted and he was forced to return to the South. Following Lee’s retreat, President Abraham Lincoln issued the Preliminary Emancipation Proclamation. At that point, the Northern Cause expanded to include the emancipation of Southern slaves.

Robert E. Lee’s First Invasion of the North

Following the victory at the Second Battle of Bull Run (August 28 to 30, 1862), Confederate General Robert E. Lee and President Jefferson Davis decided to take the war to Northern soil in the late summer of 1862.

We cannot afford to be idle, and though weaker than our opponents in men and military equipments, must endeavor to harass if we cannot destroy them. I am aware that the movement is attended with much risk, yet I do not consider success impossible.

Robert E. Lee

On September 4, the Army of Northern Virginia started crossing the Potomac River, near Poolesville, Maryland. Robert E. Lee’s First Invasion of the North was underway, setting the stage for the Battle of Antietam.

Battle of Antietam, Union Soldiers Marching into Battle, Painting
Battle of Antietam, Union Soldiers Marching into Battle. Image Source: Library of Congress.

Robert E. Lee’s Goals for the Maryland Campaign

Beyond Lee’s military goals, there were both economic and political motives that prompted his First Invasion of the North

  1. First, the Southern armies needed provisions and supplies. Taking the war north would allow Virginia farmers to harvest their crops, unmolested by Union troops. The invasion would also enable Southern troops to seize supplies from Northern farmers.
  2. Lee hoped giving Northerners a taste of war would diminish their resolve. If that happened, it might bolster the prospects of Peace Democrats in the upcoming 1862 Congressional elections.
  3. It was possible that Maryland, one of the Border States, would join the Confederacy. As a Border State, Maryland was a Slave State that remained in the Union. However, the people of Maryland were divided, which included John Wilkes Booth. Booth was an actor and staunch advocate of the Southern Casuse.
  4. A victory on Northern soil might induce European powers to lend support to the South.
Jefferson Davis, President of the Confederacy
Jefferson Davis. Image Source: Wikimedia.

Lee’s Plan for the Maryland Campaign

Lee entered Maryland and proceeded to Frederick. When he arrived, he rested his men and met with his generals to devise a plan for his campaign. By September 9, Lee drafted Special Order Number 191, which outlined his course of action. Assuming that the Federal forces near Washington were still in disarray following the Second Battle of Bull Run, Lee believed that it was safe to divide his army temporarily. Lee ordered:

  • Three columns — commanded by Lafayette McLaws, Richard Anderson, and Thomas “Stonewall” Jackson — were to march west and capture Union garrisons at Martinsburg and Harpers Ferry, Virginia (now West Virginia). There were two Union garrisons threatening his supply lines in the Shenandoah Valley, and Lee determined he had to eliminate them to avoid the possibility of his army being isolated in Maryland.
  • Lieutenant General James Longstreet to take his column, follow Jackson, and march to the vicinity of Hagerstown, Maryland. Longstreet would guard against any potential Union resistance coming south from Pennsylvania.
  • Major General D.H. Hill to take his men and follow the invasion force up the Hagerstown Road, as far as Boonsboro. Hill was to serve as a rearguard for the army’s stores and artillery.

President Lincoln Turns to McClellan

Meanwhile, sensing the vulnerability of the nation’s capital, President Abraham Lincoln reluctantly turned to Major General George B. McClellan to reinvigorate the Federal forces to stop Lee’s advance. On September 2, 1862, Lincoln placed McClellan in command of “the fortifications of Washington, and all the troops for the defense of the capital.” Known for his organizational skills, McClellan merged the Army of Virginia with his Army of the Potomac and quickly transformed the demoralized Union armies into a formidable force.

George McClellan, Portrait, Brady
George B. McClellan. Image Source: Wikimedia.

Robert E. Lee’s Lost Orders

Lee’s plan got underway on September 10, 1862, when Brigadier General John G. Walker’s Division headed west out of Frederick toward Harpers Ferry. Around noon on September 12, the last of the Confederate troops left Frederick. Four hours later, McClellan’s advance forces marched into Frederick and occupied the same campgrounds that the Confederates had evacuated. The next day, members of the 27th Indiana found a copy of Lee’s plans. They quickly passed the document up the chain of command where Union officials verified its authenticity. Upon receiving the copy of Lee’s orders, McClellan crowed:

Here is a paper with which, if I cannot whip Bobby Lee, I will be willing to go home.

George B. McClellan

Knowing Lee had divided his army, McClellan took the initiative and advanced to a position that would prevent the Confederate army from reuniting.

It is unknown when Lee realized that McClellan knew his plans. However, what is known is that by September 14 Lee was concerned the seizure of Harpers Ferry was taking longer than expected. Lee sent a dispatch urging Jackson and McLaws to finish their task quickly and to rejoin him. When Lee learned McClellan was marching west from Frederick, he ordered Hill to hold the passes at South Mountain, which separated Lee’s soldiers from the Union army.

Maryland Campaign History and Overview

Battle of South Mountain

On September 14, advance elements of McClellan’s army approached three strategic passes through South Mountain—Crampton’s, Turner’s, and Fox’s Gaps—and fighting erupted. More Union troops moved forward throughout the day and gradually forced Lee to withdraw the stubborn Confederate defenders on September 15. The Union victory at the Battle of South Mountain provided McClellan with an opportunity to crush Lee’s army before it could reunite. Characteristically, McClellan did not take advantage of the Confederates’ precarious situation. While Lee hastened to reassemble his army near Sharpsburg, Maryland, McClellan spent most of the next two days devising plans and deploying troops as they poured through the South Mountain passes.

Battle of Harpers Ferry

Without the troops delayed at Harpers Ferry, Lee knew that he had little chance of winning an engagement against McClellan’s mounting superior numbers. The Confederate general was considering ending the campaign and returning to Virginia when he received word that the Union garrison at Harpers Ferry had surrendered on September 15. The Confederate victory at the Battle of Harpers Ferry convinced Lee to stand and fight. On September 16, both armies prepared for battle the next day.

Battle of Antietam — The Bloodiest Day of the Civil War

The climactic engagement of the campaign occurred on the morning of September 17, 1862, when the Army of the Potomac and the Army of Northern Virginia met along Antietam Creek, near Sharpsburg. The pitched battle went back and forth the entire day. When the Federals were on the verge of victory, General A. P. Hill and his division arrived on the scene at approximately 4:00 p.m. after a forced march from Harpers Ferry. Hill’s arrival turned the tide and prevented a Confederate defeat. The Battle of Antietam ended as a tactical draw. However, the Union won a strategic victory because Lee’s northern advance ended. The engagement was the bloodiest single-day battle during the American Civil War. McClellan’s army of approximately 75,000 men suffered 12,401 casualties, including 2,108 killed. Lee’s smaller army of approximately 55,000 soldiers suffered 10,316 casualties, including 1,546 killed.

Battle of Antietam, Illustration, Kurz and Allison
Battle of Antietam. Image Source: Library of Congress.

Battle of Shepherdstown

Following a day of truce during which both sides recovered and exchanged their wounded and recovered their dead, Lee began withdrawing his army across the Potomac River at Boteler’s Ford near Shepherdstown, Virginia (present-day West Virginia). Once again, McClellan failed to press the issue.

After crossing the Potomac River, Lee left behind a rearguard of two infantry brigades and forty-five cannons, commanded by Brigadier-General William N. Pendleton, to hold the ford. It was not until late afternoon on September 19 that a detachment of Federal troops from Major General Fitz John Porter’s 5th Corps crossed the river, attacked the Confederate rearguard, and then withdrew. The next morning, Porter sent two divisions back across the river to establish a bridgehead for McClellan’s army.

By that time, Major General A. P. Hill’s “Light Division” had reversed course and marched back towards Shepherdstown in time to counterattack the advancing Union forces. When Porter received word that the Confederate force outnumbered his infantry on the Virginia side of the Potomac River, he ordered a withdrawal. The Confederate victory at the Battle of Shepherdstown persuaded McClellan to call off any further pursuit of Lee’s battered army, much to the consternation of President Lincoln and other federal officials. McClellan would later pay for his inertia when Lincoln dismissed him as commander of the Army of the Potomac on November 5, 1862.

Maryland Campaign Outcome

The Battle of Shepherdstown and Lee’s withdrawal from Maryland ended the Maryland Campaign. Although the fighting was over, the campaign precipitated a monumental aftereffect that altered the course of the war. With Lee’s army driven back across the Mason-Dixon Line, President Lincoln, on September 22, 1862, used his constitutional power as commander-in-chief to issue his Preliminary Emancipation Proclamation. The president’s “covenant with God,” which added freeing Southern slaves to the mission of the war, produced major political repercussions, especially in the North, and undoubtedly steeled the resolve to fight on in the South.

Maryland Campaign Significance

The Maryland Campaign was important to the outcome of the Civil War for two main reasons:

  • After the campaign was over, President Abraham Lincoln dismissed McClellan as commander of the Army of the Potomac on November 5, 1862.
  • Lincoln also employed his constitutional power as commander-in-chief to issue his Preliminary Emancipation Proclamation on September 22, 1862.

Maryland Campaign Facts

Also Known As

  • Antietam Campaign
  • Robert E. Lee’s First Invasion of the North

Date and Location

  • September 4–20, 1862
  • Maryland and present-day West Virginia

Principal Union Commanders

Principal Confederate Commanders

Union Forces Engaged

  • Army of the Potomac

Confederate Forces Engaged

  • Army of Northern Virginia

Number of Union Soldiers Engaged

  • Roughly 102,234

Number of Confederate Soldiers Engaged

  • Roughly 55,000

Estimated Union Casualties

  • 27,940 (2,673 killed; 11,756 wounded; 13,511 captured/missing)

Estimated Confederate Casualties

  • 10–20,000 (killed, wounded, captured/missing)

Maryland Campaign Timeline

These are the main battles and events of the Maryland Campaign in chronological order.

Maryland Campaign Suggested Reading

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The Maryland Campaign of 1862 by General Ezra A. Carman

Ezra A. Carman was an officer in the Union Army during the Civil War. He commanded a New Jersey infantry regiment and a brigade. Carman fought in the Maryland Campaign as the Colonel of the 13th New Jersey Infantry. After the fighting of September 17, 1862, he wrote in his diary he was preparing “a good map of the Antietam battle and a full account of the action.” In 1894, Carman was appointed as the “Historical Expert” to the Antietam Battlefield Board. Carman and the others gathered accounts from hundreds of veterans, researched thousands of letters and maps, and collected the material into the hundreds of cast iron tablets that still mark the field today. Carman also wrote an 1,800-page manuscript on the Maryland Campaign, from its start in northern Virginia through McClellan’s removal from command in November 1862. Carman’s work is available in a 3-volume set.

Citation Information

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  • Article Title The Maryland Campaign of 1862 — Robert E. Lee's First Invasion of the North
  • Date September 4–September 20, 1862
  • Author
  • Keywords Maryland Campaign, Antietam Campaign, Lee's First Invasion of the North, Battle of Harpers Ferry, Battle of South Mountain, Battle of Antietam, Battle of Shepherdstown, When was the Maryland Campaign, Who won the Maryland Campaign, What was the outcome of the Maryland Campaign
  • Website Name American History Central
  • Access Date July 14, 2024
  • Publisher R.Squared Communications, LLC
  • Original Published Date
  • Date of Last Update January 12, 2024