Military Unit Organization and the Civil War: Why the North Won?

During the American Civil War, The North fought with a marked superiority in men, material and equipment. They had massive factories churning out guns, artillery pieces and equipment. Their output far surpassed anything the Confederacy could hope to match. Unfortunately for the South, they also developed a better organizational system that took advantage of this superiority.

In March, 1862 The Union organized The Army of The Potomac around Corps formations instead of the usual Divisional command. A Corps is usually 3-4 divisions. Prior to using Corps, the Union organized around Divisions. This meant that when carrying out orders, one or two divisions would be sent and operate in conjunction. That is a decent amount of firepower, but when fighting the Confederacy, a numerically inferior foe, why wouldn’t you want to send a Corps (a much larger formation) instead of a few divisions? The Confederacy mainly fought with Brigades and Divisions and used Regiments as the maneuver element of their forces. By using Corps, the Union was able to bring more firepower to bear and neutralize the audacious field commanders of the south.

Image result for ulysses s grant

“I don’t underrate the value of military knowledge, but if men make war in slavish obedience to rules, they will fail” US Grant

Union General Ulysses S. Grant organized his Army of Tennessee and, when he took command of it, The Army of The Potomac around Corps level formations. He allowed the commanders under him to maneuver and commit entire Corps instead of just having the Corps as an organizational unit. In other words, he allowed his Army and Commanders to fight with and utilize the Corps in actual combat. In the Western Theater, General Grant swept from Tennessee down to Vicksburg and continually refined his Army and its organization, gaining valuable experience and victories along the way, while also successfully using Corps level formations to attack and maneuver. The Eastern theater was a bit of a learning experience for both the Union and the Confederacy, though…

By the time of the Battle of Antietam, The Army of Northern Virginia and The Army of The Potomac had both adopted the Corps model of organization. Previously, General Lee had used his Army of Northern Virginia in Divisional and Brigade level commands, using the Corps (or as they termed it “wings”) model only as an organizational unit, but not an actual command unit. In other words, it existed on paper, but was not utilized in “the real world”.

Those of us vaguely familiar with the Civil War remember that Antietam was a turning point in the Eastern theater; prior to Antietam the North had been outmaneuvered, outfought and generally beaten by the South. While Antietam was not a huge victory (it was really just a stalemate) by any means, the North did successfully fight against the Army of Northern Virginia, penetrate Lee’s lines and present a decent showing of themselves. The South had used Corps as a way to organize Divisions and Brigades, while The Union had committed entire Corps to the battle.

Stonewall Jackson, arguably the best field commander of the Confederacy, was in charge of a Corps during his stunning victory at Chancellorsville. Conversely, Pickett, of the infamous Pickett’s charge was only in command of a division during his disastrous charge at the Battle of Gettysburg. While there were different “divisions” and other units involved in the assault, the total manpower numbered around 12,500- the amount of men in a division. General Longstreet, the successor to Stonewall Jackson was in command of the Corps, but the Divisions were not united in a concentrated attack, the way a Corps level assault was conducted by Stonewall Jackson at Chancellorsville.

8 thoughts on “Military Unit Organization and the Civil War: Why the North Won?

  1. Paul Callahan

    As a history guy, who doesn’t have military background but is fascinated by battle history, I have a gap in my full understanding of tactics. this short article presented an accessible and informative guide to how armies are organized and utilized. Would like to read more about how this structure has worked successfully and why other organizations haven’t worked. Thanks

    Liked by 1 person

    1. Thank you for the feedback and for reading my article Paul, I really appreciate it. The themes covered in this article are recurring throughout history and I will be doing some more in depth looks at military unit organization throughout history and the why’s and how’s of the failures and successes. Stay tuned!


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    1. Regiments were a bit more fundamental than Brigades and Divisions, so they were not as prone to changing in manpower and organization. The Confederacy still used the Regiment as one of their basic warfighting units, while The Union relied on Brigades and Divisions much more.


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