Saphroneth
Lt. Colonel
- Joined
- Feb 18, 2017
Strengths at the opening of the campaign
The question of strengths in the Maryland Campaign is an extremely contentious topic, but it should really be considered to be divided into several separate questions because "how strong is X unit" has multiple possible answers.
For the Union, we are fortunate enough to have their PFD strength according to September 20 returns properly filled out. There is however no September 10 return for the full army (though there are some September 10 returns for parts of the Washington defences) and this should be kept in mind; in particular, some units joined McClellan after he marched out of Washington itself. The September 20 returns may also reflect a somewhat diminished state for some units.
For the Confederates, things are considerably more confusing.
The possible answers for the question "how strong is X unit" could have these sorts of answers:
"The unit is formed of 256 companies, meaning 25.6 full regiments of all arms".
"The unit has 21,000 men aggregate present and absent, meaning there are 21,000 men on the rolls associated with this unit who have not been struck off through death or discharge."
"The unit has 15,000 men Aggregate Present".
"The unit is a moving body of 17,000 men including non soldiers" (a situation chiefly found with the Confederates who used slaves and free blacks in their logistics train)
"The unit has 12,000 men in Union regulation PFD."
"The unit has 9,500 men who would normally be expected to form line of battle" ("effectives", which is Confederate PFD)
"The unit has currently got 7,500 men in line, after straggling and/or casualties"
Straggling can best be defined as men who are not with their unit when they should be, but who have not actually deserted - just been unable to keep up, or "wandered off" for a bit, mostly. It's attributable to the relatively incomplete discipline of the American volunteer armies, at least in extent.
What we do know is that, as of September 2nd, the effective strength of the Confederate army (about two thirds of which had just fought in Second Bull Run) was around 75,000, composed of the divisions of Jackson, Ewell, AP Hill, DR Jones, Wilcox, Hood/Evans*, Anderson, McLaws, DH Hill and Walker (of varying sizes, with Walker's division consisting of two brigades and AP Hill's divsion consisting of six) plus three sizeable brigades of cavalry under Stuart. This would equate to around 94,500 men PFD by Union measures (or another way to put it is that a force of 94,500 PFD Union troops would be expected to put about 75,000 effective men into battle under broadly normal conditions). This force could be reduced significantly by hard marching and periods of time without food, as well as by the disruptive effect of battle.
* this designation used because there was effectively an ongoing leadership dispute
Another way to put it is that the force with which Lee marched to invade Maryland consisted of approximately 2015 companies (of which 76 were artillery batteries and 124 were cavalry companies).
I should pause here to address the idea that the force post-Second-Bull-Run was much smaller than this.
The idea that it was around 50,000 (though in what category is not usually described) has come up in the past in various sources, such as Stephen W. Sears' books, but the logic involved does not hang together. Just as one example, the force which Lee had on October 10 after all the fighting of the campaign was 64,000 Confederate PFD, and given known casualties in the Maryland Campaign this would imply that there were around 75,000-80,000 in that category before the start of the campaign (depending on how many wounded had recovered by October 10). It's not really believable that the exceptionally bloody Battle of Antietam could cause an army to gain tens of thousands of men without the addition of new formed units!
There are multiple strands of evidence to support the idea that Lee's army in the Maryland Campaign was large - not necessarily larger than McClellan's, but not out of the same size class. In addition to the post-Second-Bull-Run state (which is before crossing the Potomac) there's also the post-campaign situation with add-back of casualties, the regiment counts (which are comparable for both sides), reports by individual commanders actually at Antietam (in Carman, which - with further analysis - will be addressed later) and the eyewitness reports of the moving Confederate army. While these do not agree exactly, they all line up with one another to the extent that we can be fairly confident about this statement:
When McClellan left Washington, he was facing an army of about the same size as his own force at that time.
The question of strengths in the Maryland Campaign is an extremely contentious topic, but it should really be considered to be divided into several separate questions because "how strong is X unit" has multiple possible answers.
For the Union, we are fortunate enough to have their PFD strength according to September 20 returns properly filled out. There is however no September 10 return for the full army (though there are some September 10 returns for parts of the Washington defences) and this should be kept in mind; in particular, some units joined McClellan after he marched out of Washington itself. The September 20 returns may also reflect a somewhat diminished state for some units.
For the Confederates, things are considerably more confusing.
The possible answers for the question "how strong is X unit" could have these sorts of answers:
"The unit is formed of 256 companies, meaning 25.6 full regiments of all arms".
"The unit has 21,000 men aggregate present and absent, meaning there are 21,000 men on the rolls associated with this unit who have not been struck off through death or discharge."
"The unit has 15,000 men Aggregate Present".
"The unit is a moving body of 17,000 men including non soldiers" (a situation chiefly found with the Confederates who used slaves and free blacks in their logistics train)
"The unit has 12,000 men in Union regulation PFD."
"The unit has 9,500 men who would normally be expected to form line of battle" ("effectives", which is Confederate PFD)
"The unit has currently got 7,500 men in line, after straggling and/or casualties"
Straggling can best be defined as men who are not with their unit when they should be, but who have not actually deserted - just been unable to keep up, or "wandered off" for a bit, mostly. It's attributable to the relatively incomplete discipline of the American volunteer armies, at least in extent.
What we do know is that, as of September 2nd, the effective strength of the Confederate army (about two thirds of which had just fought in Second Bull Run) was around 75,000, composed of the divisions of Jackson, Ewell, AP Hill, DR Jones, Wilcox, Hood/Evans*, Anderson, McLaws, DH Hill and Walker (of varying sizes, with Walker's division consisting of two brigades and AP Hill's divsion consisting of six) plus three sizeable brigades of cavalry under Stuart. This would equate to around 94,500 men PFD by Union measures (or another way to put it is that a force of 94,500 PFD Union troops would be expected to put about 75,000 effective men into battle under broadly normal conditions). This force could be reduced significantly by hard marching and periods of time without food, as well as by the disruptive effect of battle.
* this designation used because there was effectively an ongoing leadership dispute
Another way to put it is that the force with which Lee marched to invade Maryland consisted of approximately 2015 companies (of which 76 were artillery batteries and 124 were cavalry companies).
I should pause here to address the idea that the force post-Second-Bull-Run was much smaller than this.
The idea that it was around 50,000 (though in what category is not usually described) has come up in the past in various sources, such as Stephen W. Sears' books, but the logic involved does not hang together. Just as one example, the force which Lee had on October 10 after all the fighting of the campaign was 64,000 Confederate PFD, and given known casualties in the Maryland Campaign this would imply that there were around 75,000-80,000 in that category before the start of the campaign (depending on how many wounded had recovered by October 10). It's not really believable that the exceptionally bloody Battle of Antietam could cause an army to gain tens of thousands of men without the addition of new formed units!
There are multiple strands of evidence to support the idea that Lee's army in the Maryland Campaign was large - not necessarily larger than McClellan's, but not out of the same size class. In addition to the post-Second-Bull-Run state (which is before crossing the Potomac) there's also the post-campaign situation with add-back of casualties, the regiment counts (which are comparable for both sides), reports by individual commanders actually at Antietam (in Carman, which - with further analysis - will be addressed later) and the eyewitness reports of the moving Confederate army. While these do not agree exactly, they all line up with one another to the extent that we can be fairly confident about this statement:
When McClellan left Washington, he was facing an army of about the same size as his own force at that time.