Battle Of Antietam Casualties set out in phases

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Battle Of Antietam Casualties
Antietam Casualties (Dead and Wounded) during the Battle Of Antietam of the American Civil War

The number of casualties at the Battle of Antietam, a.k.a Battle of Sharpsburg, still stand as the highest single-day casualty total in all of American history. Concealing terrain, the number of artillery pieces involved, the desperate nature of General Robert E. Lee’s stand with the Potomac River near his back, and the determination of the Union men of Maj. Gen. George B. McClellan’s Army of the Potomac to destroy Lee’s Army of Northern Virginia before it could escape back into Virginia all contributed to the intense, close-quarter fighting and high casualties of America’s bloodiest day.

Casualty Totals for the Battle of Antietam
Exact casualty totals cannot be determined, but these numbers compiled by The Antietam Battlefield Board show where and when the greatest losses occurred.

Morning Phase: primarily north end of battlefield, Miller’s cornfield, East Woods, West Woods
UNION: Engaged, 23,600; Casualties, 7,280
CONFEDERATE: Engaged, 20,100; Casualties, 6,580
TOTAL: Engaged, 43,700; Casualties, 13,860

Mid-Day Phase: primarily center of field, Sunken Road aka Bloody Lane
UNION: Engaged, 10,000; Casualties, 2,900
CONFEDERATE: Engaged, 6,800; Casualties, 2,600
TOTAL: Engaged, 16,800; Casualties, 5,500

Afternoon Phase: primarily south end of field—Burnside Bridge, A. P. Hill’s counterattack
UNION: Engaged, 13,800; Casualties, 7,150
CONFEDERATE: Engaged, 7,150; Casualties, 1,120
TOTAL: Engaged, 20,950; Casualties, 3,720

Killed, Wounded and Missing at the Battle of Antietam
The Official Records of the War of the Rebellion give these numbers:

Killed: Union, 2,100; Confederate, 1,550
TOTAL: 3,650
Wounded: Union, 9,550; Confederate, 7,750
TOTAL: 17,300
Missing or Captured: Union, 750; Confederate, 1,020
TOTAL: 1,770

Union Total Casualties: 12,400
Confederate Total Casualties: 10,320
Combined Total: 22,720

In addition to these losses, an untold number of civilians died from disease following the battle. Every house, barn and church was turned into a hospital. Dead men and horses lay unburied for days, adding to the unsanitary conditions.

Battle of South Mountain Casualties
Three days prior to the Battle of Antietam, 12,000 Confederates fought a desperate holding action against 38,000 Federals atop South Mountain, buying time for Lee to gather his scattered army. That day’s fighting produced another 2,500 Union and 3,800 Confederate casualties.

Source all from http://www.historynet.com/battle-of-antietam-casualties