The Battle of Antietam (Sharpsburg)
September 17, 1862

Only days after his decisive victory at Second Bull Run, Confederate GEN Robert E. Lee rallied the Army of Northern Virginia (40,000+ men - MG James Longstreet and MG Thomas J. "Stonewall" Jackson - Lee's "wing" or corps commanders - two of the best in the Confederacy) for its first invasion of the North. There were several objectives, political and military: it was time to shift the burden of the battle in the East from Virginia to the North - morale in the Army of Northern Virginia was high and the South was anxious to prove that it could wage an offensive war; the decisive battle could be fought on northern soil in 1862 - the great "showdown" that had eluded Lee on the Virginia Peninsula and at Second Bull Run may be in the offing; foreign recognition and support (Britain and France) could be won with a successful campaign waged in enemy territory; and finally Maryland, a border state with considerable southern sympathies, might be encouraged to leave the Union and join the Confederacy. On 9 September Lee issued Special Order No. 191 - the famous "lost order" - and a copy unaccountably fell into Union hands (13 September). Federal commander MG George B. McClellan (75,000+ men - Army of the Potomac), groping north and west to protect Washington and Baltimore, now knew Lee's operational plans, but once again he would move too slowly and too cautiously to take full advantage of the windfall. To secure his flank and rear Lee sent Jackson to subdue the Federal garrison (12,500 men) at Harper's Ferry, VA (taken 15 September - the largest Union surrender of troops during the War). After recalling Longstreet from the vicinity of Hagerstown, MD, Lee moved (14 September) his army to three South Mountain gaps in an effort to delay the advancing Army of the Potomac. Reforming his lines after South Mountain west of Antietam Creek near Sharpsburg, MD, Lee learned that Harper's Ferry had fallen. The Army of Northern Virginia, in consolidated defensive positions, prepared for battle (15-16 September). Beginning at dawn and lasting until late afternoon on 17 September the Army of the Potomac launched five separate, disjointed attacks in three phases (MG Joseph Hooker, MG J.K.F. Mansfield, MG Edwin V. Summer, and MG Ambrose E. Burnside - corps commanders engaged at Antietam) against Lee's defenses behind (west) the creek. If McClellan had attacked Lee on 15 or 16 September, before Jackson and MG A.P. Hill could complete separate forced marches from Harper's Ferry, his army may have swept the outnumbered Confederates from the field; however, due to the untimely and uncoordinated Federal assaults, Lee was able to shift defensive forces and, with the arrival of Hill's division from Harper's Ferry at 4 PM, repulse the final Union attacks near Burnside Bridge. The next day (18 September) McClellan, reinforced and able to deploy two uncommitted corps (24,000+ men), chose not to resume the offensive. Lee's battered but defiant army slipped back during the night across the Potomac River into Virginia. Although the battle - the bloodiest single day of the War with almost 23,000 casualties on both sides - was largely an indecisive tactical struggle, it was, nonetheless, a strategic victory for the North and a turning point in the War. Antietam ended Lee's first invasion of the North, but it was not the decisive "showdown" of 1862. Maryland did not break-away, and there would be no overseas recognition for the economically beleaguered South. And as always, McClellan's conservative generalship kept the Union from a more conclusive victory; nevertheless, the events at this small town in western Maryland did give President Lincoln cause to issue (22 September) the Preliminary Emancipation Proclamation - a document with far-reaching implications here and abroad. Heretofore the War had been fought to preserve the Union, but after Antietam it also became a war to end slavery! Estimated Casualties: Union - 12,401; Confederate - 10,318.

Notes:

  1. Numbers in parentheses reflect estimated strength of armies or units.

  2. Estimated casualty figures are totals for killed, wounded, missing in action, and taken prisoner.

  3. Alternative names of battles and campaigns appear in parentheses.

  4. Military and naval rank abbreviations in text: LT - Lieutenant, CPT - Captain, MAJ - Major, LTC - Lieutenant Colonel, CDR - Commander (Navy), COL - Colonel, BG - Brigadier General, MG - Major General, RADM - Rear Admiral (Navy), LTG - Lieutenant General, VADM - Vice Admiral (Navy), and GEN - General.

  5. Army Organization: Although authorized and actual strength and the rank of the commanding officer often varied, the standard military unit during the War was the infantry regiment (1,000 men, COL commanding) which was comprised of 10 companies (100 men each, CPT commanding). 3-4 Regiments = 1 Brigade (3,000-4000 men, BG commanding). 3 (sometimes 4) Brigades = 1 Division (9000-12,000 men, BG or MG commanding). 2-4 (usually 3) Divisions = 1 Corps (18,000-24,000+ men, MG - North and MG or LTG -South commanding). 2 or more Corps = An Army (usually 20,000-100,000+ men - MG, LTG, or GEN commanding). 2 or more Armies = An Army Group (usually 100,000+ men - MG, LTG, or GEN commanding).

Sources:

Photographs courtesy of The Generals of the American Civil War Website.

Back