Battle of Chancellorsville • Tour the Battlefield • Monuments & Markers • The Armies
The armies at the Battle of Chancellorsville had evolved from a common ancestor. Their structure resembled each other in many ways. Both were organized into corps, divisions, brigades and regiments. The Federal Army of the Potomac had more of each type of unit than the Confederate Army of Northern Virginia. The South had fewer but stronger units, a trend that would continue until after Gettysburg.
Each Southern brigade averaged close to 2,000 men, while each Northern brigade only averaged 1,500. A Southern division averaged over 8,000 men, while Northern divisions averaged barely half that.
The Confederate Army of Northern Virginia (see organization)
7 divisions – 29 brigades – 57,400 men
At Chancellorsville Lee was missing a quarter of his army and one of his two senior commanders, who were detached on the Suffolk Expedition south of Richmond. Lee had hoped he could recall them if it appeared a battle was forming, but Hooker moved too fast. The result was an unusual command structure, with Lee directly commanding the two remaining divisions of the First Corps and Jackson commanding two thirds of the army. It worked because Jackson excelled as an independent commander, although when he marched off the field and into the Wilderness with the bulk of the army to execute his flank attack it must have given Lee some thoughtful moments.
The Federal Army of the Potomac (see organization)
24 divisions – 65 brigades – 97,400 men
Hooker had the opposite problem. With eight corps commanders (counting the cavalry corps), he had too many direct subordinates to oversee effectively. He tried temporarily subordinating one corps commander to another and detaching a division from one corps to reinforce another, but these temporary command relationships also had problems. This lack of control had fatal consequences when Howard let his 11th Corps dangle its flank in the air with Jackson loose on the field.
After Chancellorsville
Both armies would modify their structures as the war went on. One result of the “irreplaceable” Jackson’s death was the reorganization of Lee’s army, which added a third corps and redistributed the infantry. The result was three corps of three divisions each. By the end of 1863 the Confederate cavalry would expand to a corps.
The Army of the Potomac went the other way and condensed its structure. Two corps permanently left the army for the Western Theater in the fall. In March of 1864 the five remaining infantry corps – two of which, the 1st and 3rd, having been badly depleted at Gettysburg – consolidated into three. For a short time in the opening stages of the 1864 Overland Campaign both armies had evolved to the the same basic structure – three infantry and one cavalry corps.