Schematic plan · American Civil War

Battle of South Mountain

14 September 1862
Maryland
Victory for USA

All battles The event in the chronicle Wikipedia

A schematic plan, generated from the statistics of the CAA Database of Battles: the armies' size and width, the hours of fighting, the plan of attack and the outcome are as recorded; the ground and the positions are not.

USA (US Army of the Potomac, 28,480 men under Mcclellan) attacked Confederacy (Cs Army of Northern Virginia (-), 17,852 men under D. H. Hill) in Maryland. The CAA Database of Battles records 13 hours of fighting on a front of 3 km, a frontal attack, single envelopment, left flank against hasty defense, and that USA won. Losses: USA 1,813 (6%), Confederacy 2,685 (15%).

This plan is generated from those figures. It shows the shape of the battle the database describes: the size and width of the armies, the plan of attack and the outcome. It does not show where the units actually stood.

The armies

USA

Mcclellan

Unit	Arm	Men
USA left wing	Infantry	6,738
USA centre	Infantry	8,984
USA right wing	Infantry	6,738
USA reserve	Infantry	5,615
USA artillery (27 guns)	Artillery	405
Mcclellan	Commander	—
In this plan		28,480

Confederacy

D. H. Hill

Unit	Arm	Men
Confederacy left wing	Infantry	4,091
Confederacy centre	Infantry	5,455
Confederacy right wing	Infantry	4,091
Confederacy reserve	Infantry	3,409
Confederacy cavalry of the left	Cavalry	350
Confederacy cavalry of the right	Cavalry	350
Confederacy artillery (7 guns)	Artillery	105
D. H. Hill	Commander	—
In this plan		17,851

What the sources report

	USA	Confederacy
Strength, this plan	28,480	17,852
Losses, this plan	1,813	2,685

In the CAA Database of Battles

CDB90 no. 190, “South Mountain”, compiled for the US Army to study what decides battles. These are the figures a what-if engine can be calibrated against.

Fighting: 13 hours
Winner: the attacker
Terrain: Rugged, Mixed
Weather: Dry, Sunny, Temperate, Autumn, Temperate
Defender’s posture: Hasty defense
Front width: 3 km (attacker), 2 km (defender)

Force	Strength	Losses	Horse	Guns	Plan and outcome
USAattacker	28,480	1,813	—	27	Frontal attack; Single envelopment; Left flank; Penetration; Pursued
Confederacydefender	17,852	2,685	700	7	Defensive plan; Withdrew

Attacker’s advantages intelligence +1 · initiative +1

CDB90 (US Army Concepts Analysis Agency, 1990), tidy edition by Jeffrey B. Arnold; data under ODC-BY 1.0.

Notes

On this reconstruction

Generated automatically from the statistics in CDB90. Frontages, depths, distances, the order of events and the terrain are schematic: they follow the recorded strengths, front widths, hours of fighting, tactical plan and outcome, not maps or accounts of the battle. The sources give no hours; the timing is conjectural.

Sources

US Army Concepts Analysis Agency; tidy edition by Jeffrey B. Arnold, CAA Database of Battles (CDB90), no. 190 · ODC-BY-1.0Strengths, losses, front widths, hours of fighting, tactics and outcome.
Wikipedia contributors, Battle of South Mountain · CC-BY-SA-4.0

Facts gathered from Wikidata (CC0), Wikipedia (CC BY-SA 4.0) and Wikimedia Commons (licence per file); the plan and its text are timeastra’s own.