After the Battle of Cedar Mountain, General Pope was surprised to learn that General Banks had less than 8,000 men in the battle. Just 10 days earlier Pope’s staff had compiled the strength report of the Army of Virginia for the month of July and Banks’ Corps was shown as having 14,785 present for duty. Now Banks was claiming that only about ½ that number were in the battle on August 9, 1862. Pope wondered “how General Banks could have been so greatly mistaken as to the forces under his immediate command.” But there had not been a mistake in the numbers – both the July 31 report and the estimate of strength in battle were correct. How could that be? What had happened to the rest of the men?
Pope seems to have lost sight of what went into the July 31 consolidated strength report. It included everyone who was part of the commands that made up his army. Units detailed to a detached assignment would still be counted as long as they were still officially part of the army. A review of the composition of Banks command reveals that a number of units had been assigned other duties prior to the battle.
The July 31 report includes a footnote stating that the total included Hatch’s cavalry brigade. In early August, Buford took over from Hatch and the cavalry operated separately from the Corps. Thus, while accurately counted in the July strength report, it should have been understood that these men were not with the infantry at the time of the battle.
Additionally, several infantry regiments had been detached prior to the battle. When Banks held the northern end of the Shenandoah Valley in June, the 29th Pennsylvania was assigned to guard the crossings of the upper Potomac and, as Banks moved away, it was left behind. General Williams wrote in his report of Cedar Mountain that the 29th Pennsylvania was “nominally attached“ but “has been on de-tached service some months”. When Banks moved from the Shenandoah east over the Blue Ridge during July, Pope directed that a regiment and a battery be left to garrison Front Royal — the 3rd Delaware was detached and assigned to Front Royal. In addition, as Pope advanced his army into central Virginia he pulled units from Banks Corps to protect his supply line. On his order, the Purnell Legion had been assigned to guard the Orange and Alexandria Railroad between Catlett’s Station and Culpeper. Likewise the 60th New York had been posted at Warrenton Junction. Finally, on the day of the battle, the 28th Pennsylvania had been sent to Thoroughfare Mountain to reestablish the signal station. By this series of detachments 5 infantry regiments that were included in the July 31 strength report were absent from the battle.
Furthermore, sickness in early August would have further reduced the number of men who could be brought to the front. For example, a history of the 111th Pennsylvania states that “when the regiment moved for Cedar Mountain, on the 6th of August, large numbers were left in the hospital.” It was the first campaign for several of the regiments and the summer heat of Virginia can be rough on the unaccustomed.
Taken together, the dispersal of the Corps through detachments and disease reduced its battle strength significantly. If it had been as strong as the July 31 strength report implies, the Corps might have been able to stand up to Jackson. But with only half as many men as reported at the end of July, Banks was overpowered by Jackson’s much larger force. Assigning units to detached service may seem innocuous at the time but, as more and more assignments are made, these detachments add up to a substantial number of men. Pope should have been aware of this, particularly since most of the detachments were at his direction. But Pope was struggling to manage the complexities of a large army, a weakness that would become all too real by the end of August.