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Schematic plan · American Civil War

Battle of Antietam

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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.
Rolling, Mixed groundCentreLeft wingRight wingReserveCentreLeft wingRight wingReserveHorseHorseLee02 km4 kmN

USA (US Army of the Potomac, 90,000 men under Mcclellan) attacked Confederacy (Cs Army of Northern Virginia, 46,000 men under Lee) in Maryland. The CAA Database of Battles records 11 hours of fighting on a front of 6.4 km, a frontal attack, double envelopment against hasty defense, and that Confederacy held. Losses: USA 12,410 (14%), Confederacy 13,700 (30%).

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

UnitArmMen
USA left wingInfantry20,520
USA centreInfantry27,360
USA right wingInfantry20,520
USA reserveInfantry17,100
USA cavalry of the leftCavalry2,250
USA cavalry of the rightCavalry2,250
McclellanCommander—
In this plan90,000

Confederacy

Lee

UnitArmMen
Confederacy left wingInfantry11,040
Confederacy centreInfantry14,720
Confederacy right wingInfantry11,040
Confederacy reserveInfantry9,200
LeeCommander—
In this plan46,000

What the sources report

USAConfederacy
Strength, this plan90,00046,000
Losses, this plan12,41013,700

In the CAA Database of Battles

CDB90 no. 191, “Antietam (Sharpsburg)”, compiled for the US Army to study what decides battles. These are the figures a what-if engine can be calibrated against.

Fighting
11 hours
Winner
the defender
Terrain
Rolling, Mixed
Weather
Dry, Sunny, Temperate, Autumn, Temperate
Defender’s posture
Hasty defense
Front width
6.4 km (attacker), 4 km (defender)
ForceStrengthLossesHorseGunsPlan and outcome
USAattacker90,00012,4104,500—Frontal attack; Double envelopment; Repulse; Stalemate
Confederacydefender46,00013,700——Defensive/offensive plan; Withdrew

Attacker’s advantages momentum +1 · 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

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.