Mansfield, Steven L. Ossad, Graphite on paper, 2006

The Opposing Armies

Army Organization
Union Army of the Potomac was organized into 6 infantry corps and 1 cavalry division. Artillery was organized into batteries of 4-6 guns each, with 2 or more batteries assigned to each of the Army's 18 divisions, which numbered 85,000 men at Antietam.

Confederate Army of Northern Virginia consisted of 2 "commands" comprising a total of 9 infantry divisions and 1 cavalry division. Corps came after the Battle of Antietam. Artillery batteries were assigned to each of the army's divisions and to the army's reserve artillery. Lee commanded 60,000 men, though only about 40,000 actually participated.

Weapons & Branches

Maryland Campaign, 1862

US Army Maps of the Campaign

Antietam Timeline

Gods and Generals, Mort Kunstler, 2003

4-7 September 1862
The Army of Northern Virginia, commanded by General Robert E. Lee, crosses the Potomac River near Leesburg and marches to Frederick, Maryland.

The Army of the Potomac, commanded by Maj. Gen. George B. McClellan, leaves Washington in pursuit of Lee.

Battle of Antietam Postage Stamp. 2012

9 September
Lee issues Special Orders 191, detailing his plan to capture Union garrisons at Martinsburg and Harper's Ferry.

10 September
Lee and Maj. Gen. James Longstreet march to Hagerstown.

Maj. Gen. D. H. Hill's division halts at Boonsboro as rear guard.

Maj. Gen. Thomas J. Jackson marches to capture the Union garrison at Martinsburg.

The divisions of Maj. Gens. Lafayette McLaws and Richard H. Anderson approach Harper's Ferry from the east.

Brig. Gen. John G. Walker's division crosses the Potomac River into Virginia and approaches Harper's Ferry from the south.

12 September
The Army of the Potomac begins arriving at Frederick.

Jackson reaches Martinsburg, but the Union garrison flees to Harper's Ferry.

13 September
McClellan arrives at Frederick.

A soldier in McClellan's army finds a copy of Lee's Special Orders 191. The document is given to McClellan, who plans to attack the Confederates the following day at South Mountain.

Jackson marches from Martinsburg to Harper's Ferry.

In the evening Lee receives information from Maj. Gen. James E. B. Stuart that McClellan's army has arrived at Frederick and that the enemy has a copy of Special Orders 191.

To delay an expected Union advance, Lee orders D. H. Hill to defend Turner's and Fox's Gaps on South Mountain. Longstreet is sent to support Hill. McLaws sends a portion of his command to defend Crampton's Gap.

14 September
The siege of Harper's Ferry begins.

The Battle of South Mountain. Union forces take Crampton's Gap.

During the night Lee decides to withdraw his outnumbered forces from Turner's and Fox's Gaps and falls back to Sharpsburg.

15 September
Lee, along with Longstreet, the divisions of Brig. Gen. D. R. Jones and D. H. Hill, and part of Stuart's cavalry, arrives at Sharpsburg.

Harper's Ferry surrenders. Lee orders the Confederate troops there to march to Sharpsburg as soon as possible. Maj. Gen. Ambrose P. Hill's division remains at Harper's Ferry to parole prisoners and gather supplies.

The Army of the Potomac arrives near Sharpsburg. McClellan replaces Maj. Gen. Ambrose E. Burnside with Maj. Gen. Joseph Hooker in command of the army's right wing and puts Burnside in command of the left wing.

16 September
0730: Jackson's command reaches Sharpsburg, reuniting with D. H. Hill's division

Walker's division arrives at Sharpsburg

1530-1600: Hooker's I Corps crosses Antietam Creek north of Sharpsburg to turn Lee's left flank. A portion of Brig. Gen. George G. Meade's division, leading Hooker's corps, skirmishes with Brig. Gen. John B. Hood's division near the East Woods

In response to Hooker's request for reinforcements, McClellan orders XII Corps, commanded by Maj. Gen. Joseph K. F. Mansfield, from the center to the right wing.

Lee sends Jackson, with his divisions commanded by Brig. Gens. John R. Jones and A. R. Lawton, to support Hood. Walker's division remains in reserve south of the town.

1930: McClellan, after learning that Harper's Ferry has surrendered, orders Maj. Gen. William B. Franklin's VI Corps to join the army at Sharpsburg.

2400: Mansfield's XII Corps crosses Antietam Creek to join Hooker's I Corps.

The Battle of Antietam
17 September
0600: McLaws' and R. H. Anderson's divisions arrive at Sharpsburg.

Hooker's I Corps begins its attack south on Hagerstown Pike and Smoketown Road, initially meeting with great success at the Cornfield.

0700: Called to assist by Jackson, whose lines are collapsing, Hood's division launches a counterattack from the West Woods against Hooker's I Corps in the Cornfield.

0730: Acting on orders received the night before, A. P. Hill's division begins a forced march from Harper's Ferry to Sharpsburg.

Mansfield's XII Corps arrives in the East Woods. Brig. Gen. Alpheus S. Williams' division of the XII Corps drives Hood's division from the Cornfield back into the West Woods. Mansfield is mortally wounded, and Williams assumes command of the division.

0800: Maj. Gen. John Sedgwick's and Brig. Gen. William H. French's divisions of Sumner's II Corps cross Antietam Creek to support Hooker's I Corps. Sumner leaves behind his third division, command by Maj. Gen. Israel B. Richardson, to guard artillery.

Ride to Glory, Dale Gallon, 1992

0900: Sedgwick's division attacks into the West Woods. French's division attacks at the Sunken Road against the division of D. H. Hill. Hill sends an urgent request to Lee for reinforcement.

One of Sedgwick's regiments, the 34th New York Infantry, becomes separated from the rest of the division and halts near Dunker Church, where it finds the 125th Pennsylvania Infantry of Williams' division, which had ended up there some time earlier.

Brig. Gen. Isaac P. Rodman's division of Burnside's IX Corps is sent to outflank the lower bridge by crossing Antietam Creek at Snavely's Ford.

Brig. Gen. George S. Greene's division of the XII Corps reaches the plateau east of the West Woods.

Hooker is slightly wounded, and Meade assumes command of the I Corps.

0930: Sedgwick's division is driven out of the West Woods by the division of Walker, sent from its reserve position south of Sharpsburg; the division of McLaws, newly arrived from Harper's Ferry; the brigade of Brig. Gen Jubal A. Early, from its station west of the West Woods; and the brigade of Col. G. T. Anderson of D. R. Jones' division. The Confederate advance into the Cornfield is stopped by Union artillery and Williams' division, which had remained in the Cornfield.

1000: D. H. Hill's division, defending the Sunken Road against French's attack, is reinforced by the division of R. H. Anderson, which had just arrived from Harper's Ferry.

Spearheaded by the 11th Connecticut Infantry, the IX Corps attack on Brig. Gen. Robert Toombs' brigade at the lower bridge begins.

1030: After crossing Antietam Creek, Richardson's division of the II Corps joins French's attack on the Sunken Road.

Greene's division occupies the West Woods.

1100: The 2d Maryland and 6th New Hampshire Infantries of the IX Corps unsuccessfully attempt to cross the lower bridge.

Greene's division withdraws from the West Woods and falls back to the East Woods. Walker's division reoccupies the West Woods.

The 27th North Carolina and 3d Arkansas Infantries, along with portions of other Confederate commands, attack the right flank of French's division. Maj. Gen. William F. Smith's division of the VI Corps drives the Confederates into the West Woods.

1230: D. H. Hill's Confederates withdraw from the Sunken Road. Richardson's division pursues them, but McClellan orders it to halt its advance, inadvertently saving Lee's center.

Will You Give Us Our Whisky Now, Don Stivers, 1995

1300: The 51st New York and 51st Pennsylvania Infantries of the IX Corps cross the lower bridge. The remainder of the IX Corps begins to cross the bridge.

South of the lower bridge, Rodman's division crosses Antietam Creek at Snavely's Ford.

North of the lower bridge, elements of the 28th Ohio Infantry cross Antietam Creek.

With Union troops above, below, and across from him, Toombs withdraws to Sharpsburg.

1430: A. P. Hill's division begins arriving near Sharpsburg.

1500: Having finished crossing Antietam Creek, the IX Corps advances on Sharpsburg.

1600: A. P. Hill's division attacks the left flank of the IX Corps and successfully halts the Union advance toward the town.

1700: The IX Corps falls back to the lower bridge.

18 September
McClellan decides not to attack this day but instead issues orders to attack on 19 September.

Lee wishes to renew the fight, but he calculates that the odds are too much against him and withdraws his army back into Virginia during the night.

19 September
In the morning McClellan learns that the Confederates withdrew during the night. He chooses not to pursue them.

Battery Longstreet, Don Troiani, 2001

Bringing the Boardroom to the Battlefield

The Battle of Antietam Corporate Staff Ride

What is a Corporate Staff Ride & What Does it Give You

Utilizing an experiential-learning approach and the setting of an actual battlefield, the Applied Battlefield Concepts™ Corporate Staff Ride is a short duration, top-level management development and leadership training tool that delivers a uniquely powerful and rewarding team-building experience. It is a proven, cost-effective, adaptable, repeatable and flexible solution for meeting internal training metrics and broader goals for improvements in decision making across the entire enterprise.

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The Battle of Antietam Corporate Staff Ride offers a rich environment for an experiential training experience where war functions as a metaphor for competitive conflict. The complex interplay of political and economic factors, personality conflicts, rapidly changing organizational alignments, and desperate choices provide a dramatic setting for examining decison-making under the most critical and dynamic circumstances imaginable.

The Corporate Staff Ride is based on the perspective of a Civil War Corps or Division commander and his staff and subordinates. Therefore, the number of attendees must be limited to 15, with no more than five from any one organization. There is no restriction on job function, organizational level, or any other personnel variable.

Why Antietam? The Decisive Battle of the Civil War

Course of the War in 1862 Antietam marks a clear turning point in the strategic fortunes of the Confederacy in its struggle for independence. During the spring and summer months of 1862, the resurgent southern forces enjoyed an unbroken string of successes, reversing the Union’s tide of victories in the early part of the year. In the Western Theater, the euphoria of the Union victories at Forts Donaldson and Henry and at Shiloh, had given way to stalemate.

Meanwhile, in the East, Thomas “Stonewall” Jackson had humiliated several Federals armies in his brilliant Shenandoah Valley campaign and General George McClellan’s drive on Richmond had ended in bloody failure. In the latter campaign a new Confederate hero had emerged – Robert E. Lee – and he was anxious to press his advantage. Over the hill, there was dissension in the Union high command and no one seemed able to face the growing power of Lee’s magnificent Army of Northern Virginia.

Robert E. Lee, Commander, Confederate Army of Northern Virginia

On the political front, during the spring and summer of 1862, the major European powers - especially England - were following events on the battlefield closely. Pressure was building for intervention in the dispute as “honest brokers,” thus effectively supporting the Confederate States’ claim to sovereignty. Abraham Lincoln’s plan to free the slaves, and elevate the struggle to a higher moral plain, was hostage to the Union’s battlefield fortunes, and they looked increasingly bleak. Still worse, mid-term Congressional elections in November might signal a repudiation of the administration's strategy and a register a negative vote of confidence in its leadership.

At the end of August, John Pope - a hero of the West - had led the Union Army of Virginia to bloody failure for the second time along Bull Run creek near Manassas, Virginia. To restore confidence to the badly shaken and demoralized troops, Lincoln had no choice but to recall the controversial McClellan who set about reorganizing the remnant of three bloodied and demoralized armies. It would be no small task and Lee had the initiative. Even the organizational genius of "Little Mac" would be hard-pressed to regain the initiative.

George B. McClellan, Commander, Union Army of the Potomac

By the beginning of September, Lee, seeing the opportunity to score a decisive military and political victory, headed north into Maryland, hoping to defeat McClellan - this time on Union soil – thereby precipitating a crisis that would end the war and establish Southern independence.

Nineteenth Century Tactics
The tactical legacy of the 18th century had emphasized close-order formations of soldiers trained to maneuver in concert and fire by volleys. These "linear" tactics stressed the tactical offensive. Assault troops advanced in line, two ranks deep, with cadenced steps, stopping to fire volleys on, command and finally rushing the last few yards to pierce the enemy line with a bayonet charge.These tactics were adequate for troops armed with single-shot, muzzle-loading smoothbore muskets with an effective range of about eighty yards. The close-order formation was therefore necessary to concentrate the firepower of these inaccurate weapons. Bayonet charges might then succeed because infantry could rush the last eighty yards before the defending infantrymen could reload their muskets after firing a volley
The U.S. Army's transition from smoothbore muskets to rifled muskets in the mid-nineteenth century would have two main effects in the American Civil War: it would strengthen the tactical defensive and increase the number of casualties in the attacking force. With a weapon that could cause fatalities out to 1,000 yards, defenders firing rifles could decimate infantry formations attacking according to linear tactics. Later in the Civil War the widespread use of the rifled musket caused infantry assault formations to loosen up somewhat, with individual soldiers seeking available cover and concealment. However, because officers needed to maintain visual and verbal control of their commands during the noise, smoke, and chaos of combat, close-order tactics to some degree would continue to the end of the war. Rapid movement of units on roads or cross country was generally by formation of a column four men abreast. The speed of such columns was prescribed as two miles per hour.

Upon reaching the field each regiment was typically formed into a line two ranks deep, the shoulders of each man in each rank touching the shoulders of the man on either side. A regiment of 500 men (250 men in each rank) might have a front of about 200 yards. Both ranks were capable of firing by volley or individual fire.

In Civil War battles, as in any large organized competition, the effectiveness of the commanders’ staff was a major determinant of success or failure. Our conception of the military staff is the result of more than a century and a half of evolution, but the major elements were already present in 1862. At that time, however, no guidelines for structure, training, or procedures were established. While the commander retained control of crucial staff functions - especially operations and intelligence – the growing complexity of warfare was already starting to overwhelm any one commanders’ ability to control a large formation. The typical Civil War staff structure was defined by General-in-Chief Winfield Scott in 1855 and was organized into two elements: a “general staff” and a “staff corps.” The typical staff functions were Assistant Adjutant General, Assistant Inspector General, Engineer, Ordnance, Quartermaster, Subsistence, Medical, Pay, Signal, Provost Marshal, Chief of Artillery

Chief of Staff
Even though many senior commanders had a chief of staff, his function was not uniform and seldom did he achieve the central coordinating authority of the chief of staff in modern headquarters. This position, along with most other staff positions, was used as an individual commander saw fit, making staff responsibilities somewhat different under each commander. This inadequate use of the chief of staff was among the most important shortcomings of staffs during the Civil War. An equally important weakness was the lack of any formal operations or intelligence staff. Liaison procedures were also ill defined, and various staff officers or soldiers performed this function with little formal guidance. Miscommunication or lack of knowledge of friendly units proved disastrous time after time.

Although some staffs became truly effective, that was more a function of the experience of the individuals and less the result of effective staff procedures or guidelines. Because of the hurried way in which the Army of the Potomac was reorganized just prior to Antietam, the staff work of the Union side was particularly poor. The Army of Northern Virginia, operating successfully for several months under Lee and his principal commanders, thus enjoyed a significant organizational advantage over its adversary.

Military Intelligence
During the Civil War, from 1861-1865, both the Union and the Confederacy engaged in clandestine activities. Hot-air balloons – the forerunners of spy planes and today’s satellites – were used to monitor troop movements and less visible operations also gleaned important intelligence on both sides.

Though neither army had a formal military intelligence service, both sides fully used spies, scouts, captured documents and mail, intercepted and decoded telegrams, newspapers, and interrogations of prisoners and deserters.

The Union’s principal spymasters were Allen Pinkerton and Lafayette Baker, both of whom specialized in counterespionage, and military officers George Sharpe and Grenville Dodge. The Confederacy had a looser array of secret operatives that collected intelligence and conducted sabotage and other covert actions. Three of the South’s most celebrated agents were women: Rose Greenhow, Belle Boyd, and Nancy Hart. In 1864, Confederate operatives tried to organize antiwar elements in Indiana, Illinois, and Ohio in a movement to leave the Union. They also set fires in New York City in an attempt to burn down the huge manufacturing hub of the north.

Both Union and Confederate agents operated abroad spreading propaganda and jockying for commercial and political support. Overall, the Union was more effective at espionage and counterintelligence, while the Confederacy had more success in special operations. The hard-won expertise and organization built up during the Civil War would be demobilized and dispersed following the South’s surrender, but a foundation for the future of intelligence had been set. (Source: CIA)

At the Battle of Antietam, the Army of the Potomac had an estimated 293 guns, 166 rifled. Although Antietam Creek physically separated many Union guns from the battlefield proper, many guns east of the creek could fire on Confederate positions along Hagerstown Pike. On the morning of 17 Sept approximately 90 Union guns were operating on the west side of the creek, mostly on the Union right flank north of Dunker Church. More guns were sent to the battlefield during the day, and by evening there were approximately 162 Union guns west of Antietam Creek. On 17 September the Army of Northern Virginia had an estimated 246 guns, of which 82 were rifled, 112 smoothbore, and 52 of unknown type. The Confederates reported having captured 73 guns at Harper's Ferry on 15 September, but none were assembled into batteries in time to be used in the Battle of Antietam.

The artillery of both armies was organized into batteries of 4-6 guns with a captain and 2 lieutenants, each commanding a 2-gun "section." Each gun made up a platoon, under a sergeant with 8 crewmen and 6 drivers. For transport, each gun was attached to a 2-wheeled cart, known as a limber and drawn by a 6-horse team. The limber chest carried 30-50 rounds of ammunition, depending on the size of guns. In addition to the limbers, each gun had at least one caisson, also drawn by a 6-horse team. The caisson carried additional ammunition in 2 chests, as well as a spare wheel and tools. A horse-drawn forge and a battery wagon with tools accompanied each battery. A battery at full regulation strength included all officers, noncommissioned officers, buglers, drivers, cannoneers, and other specialized functions and might exceed 100 officers and men. With spare horses included, a typical 6-gun battery might have 100-150 horses.

A battery could unlimber and fire an initial volley in about one minute, and each gun could continue firing two aimed shots a minute. A battery could "limber up" in about one minute as well. The battery practiced "direct fire": the target was in view of the gun. The prescribed distance between guns was fourteen yards from hub to hub. Therefore, a six-gun battery would represent a front of about 100 yards.

Antietam Staff Ride Sources

Ballard, Ted US. Army Center of Mil History. The Battle of Antietam Staff Ride, 2007 (online)

Bell, Raymond E., Jr. “Reserve MP Brigade Studies Antietam.” Army Hist (Fall 1989): pp. 12-14

Fuller, John D. "Battlefield Terrain Study: Burnside's Attack Against the Confederate Right at Antietam." Paper, AWC, 1985. 183 p.

Luvaas, Jay, & Nelson, Harold W. eds. The U.S. Army War College Guide to the Battle of Antietam: The Maryland Campaign of 1862. Carlisle, PA: South Mt, 1987. 310 p

Manguso, John M. "Civil-Military Operations-At Antietam?" Army Hist (Fall 1994): pp. 26-28.

Simmons, Edwin H. "Marine Officers Refight Antietam." Mar Corps Gaz 72 (Jun 1988): pp. 30 33.

Springer, Carl D. The Antietam Staff Ride: An Interactive, Computer-Driven Guide to the Battle of Antietam. Student project, AWC, 1992. 109 p.

U.S. Army Chaplain Center/​School. Selected compilation of materials for Antietam staff ride, 1994. ca 125 p.

U.S. Army. Fort Belvoir. “Antietam Historical Battlefield Tour: Participants’ Information Packet.”ca. 70 p.

Antietam Computer Wargames

Sid Meier's Antietam

Sources for Visiting Antietam & Other Sites of the Campaign

Updated: January 10, 2016

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