Antietam Questions and What if

This alleged incident was a fabrication >20 years after the event.

In the Antietam Campaign:
Regimental historian (then) Colonel Thomas M. Anderson later said ...
"In the great battle of September 17th, the Regular Division was held in reserve and in support of the reserve artillery until about two o'clock in the afternoon, when Capt. Hiram Dryer was ordered to cross the Antietam creek with the 2d and 10th, the 4th, 12th and 14th Infantry."

"These regiments supported Tidball's batteries, and about sundown advanced and easily drove back the enemy into the village of Sharpsburg. Captain Dryer did not feel authorized to go further without orders, and applied for permission to press his attack. It appears from official reports that General Pleasanton also advised an advance. General Sykes told the writer after the war that it was on this occasion that General Fitz John Porter reminded General McClellan that his corps was the last reserve of the last Army of the Republic. It is needless of course to speculate on what might have been, but this can be said, that the Regular Division was that day in its best condition."

"Captain Dryer rode into the rebel lines and saw that there were but two regiments and a battery left in the centre. That night there was gnashing of teeth in the Regular camp." 2
 
General Sykes told the writer after the war that it was on this occasion that General Fitz John Porter reminded General McClellan that his corps was the last reserve of the last Army of the Republic.
Even assuming the rest of it is true, this is written without clarity. Porter said "I command the last reserve of the last Army of the Republic", but he did not say it was corps strength and that's because there was much less than a corps left. In fact, there were two brigades left (two of Morell's), everything else was doing things.
 
Thomas Anderson is the source of the confabulation, yes.

Anderson's status was due to family connections. He was the nephew of "Major" (regular Brigadier-General) Robert Anderson, the defender of Fort Sumter. Thomas Anderson enlisted as a private in Coy A, 6th Ohio Volunteers. However his uncles skyrocket to BG meant he was able to find a more suitable slot for his nephew, and less than a month into the war Thomas was a regular Captain in the new 12th United States Infantry. Due to everyone above him with real experience being assigned to command regiments, there were only three captains left in 2nd Bn, 12th US by September '62 and he was senior.

Robert Anderson was thick with Pope, and by connection so was Thomas. What happened in the late 1880's is all related to FJ Porter's reinstatement in the army.

In 1886 Charles Coffin, a journalist at Antietam, wrote "Antietam Scenes" for the Century Magazine. He opined that it was inexplicable that the 5th Army Corps didn't attack after Richardson's Division carried the sunken lane. However, he himself stated in his article that what he was reporting was his recollection, and it was largely at odds with the primary observations made 24 years earlier.

Enter Thomas Anderson. Reading Coffin's article he penned his own, and he did this to make Porter the architect of the lack of commitment. To do this he wrote a confused tale set some four hours after the sunken lane collapsed and Coffin opined that 5th Corps should have attacked. Both Fitz John Porter and William Powell (then AAG of Buchanan's brigade) actually replied and denied the incident (and you'll note Anderson's AAR is addressed to Powell).

William Powell is particularly important. In his reply, published in the Century, Powell was circumspect and assiduously avoided calling Anderson a liar as both were serving colonels. He revealed a little more in his History of the Fifth Army Corps, including that he himself carried the note from General Sykes to Capt Dryer to pull back from his exposed position.

In fact what happened is roughly this:

The advance of the regular infantry in the centre was ordered by McClellan. Sykes objected, but McClellan insisted, and also ordered that two of Morell's brigades march to Sumner's aid. He himself then rode over to Sumner and is absent for the rest of the drama. Porter has roughly 4,000 infantry left in the vicinity of the Porter Bridge. (Powell laments Humphrey's not being there, as the camp talk was that if they were up the corps could have attacked)

Roughly 2/3rds of the regulars were sent over the bridge, and Capt Dryer was the ranking officer present. Lt Poland's battalion had advanced as skirmishers and Dryer spotted 12 guns on a ridge a mile to his front supported only by "two regiments" and decided to charge them. Lt Poland objected and sent a note back to Buchanan to ask for confirmation (not Capt Blunt as Anderson remembered).

Buchanan was with Sykes and Powell when the note was received and Powell was sent forward to relieve Dryer of his command and pull the regulars back, as Burnside had collapsed on their left. Dryer went back to see Sykes and it was an "interview without coffee".
 
Lt John S. Poland's Official Reports

Reports of Sepember 22 & 24, 1862 of Antietam and Shepherdstown

BIVOUAC OPPOSITE SHEPHERDSTOWN, W. VA.,
September 22, 1862.

Second Lieutenant E. E. SELLERS,
Acting Assistant Adjutant-General, Second Brigade Regulars.

SIR: I have the honor to report the part taken by the battalion of Second and Tenth Infantry in the engagement on the 17th instant at Sharpsburg, Md.

My command consisted of nine companies Second Infantry, commanded as follows: Company A, First Sergt. Thomas Byrne; Company B, First Lieutenant William F. Drum, Second Infantry; Company C, Second Lieutenant Abraham Grafius, Second Infantry; Company D, First Lieutenant George H. McLoughlin, Second Infantry; Company E, First Lieutenant Charles M. Freeman; Company G, Second Lieutenant Claude S. Robertson, Tenth Infantry; Company F, First Lieutenant J. W. Gray, Eleventh Infantry; Company I, First Lieutenant S. A. McKee, Second Infantry; Company K, Second Lieutenant Robert G. Wells, Tenth Infantry, and three companies Tenth Infantry, united under command of First Lieutenant George S. Lauman, Tenth Infantry.

By order of Major Lovell, Tenth Infantry, commanding Second Brigade Regulars, I moved across Antietam Creek by the turnpike [Middle] bridge to support Captain Tidball's battery, then hard pressed by the enemy's sharpshooters. On arriving near the battery on left of the turnpike I halted the command, being ordered to report to General Pleasonton for further instructions. While seeking him, I received his order through Lieutenant Cutting, acting assistant adjutant-general to Brigadier-General Sykes, to throw forward a line of skirmishers to drive back the enemy. Captain Tidball, who was relieved by Captain Robertson's battery, then retired. Four companies from the left deployed as skirmishers, when Captain Robertson withdrew his battery. A lieutenant-colonel of cavalry desired me to relieve a party of his command with my infantry, which I did. Captain Randol, First Artillery, brought up his battery of Napoleon guns, and occupied the position formerly occupied by Captains Tidball and Robertson. My skirmishers were advanced in front of this position from 300 to 400 yards. Five companies were held as reserve, and for any disposition that might be required. Captain Randol, finding his battery could effect nothing, withdrew it, and advanced Lieutenant Van Reed's battery to the right of the turnpike.

I then sent a note to Major Lovell explaining my position. Captain Dryer, Fourth Infantry, came up, stating he had an order to take command of all the skirmishers. By his direction I deployed the force held in reserve, and advanced them on the line occupied; then threw forward the whole line to a fence along a road running perpendicularly to the turnpike and to the left. Lieutenant McKee, commanding Companies I and A, Second Infantry, while deploying to the front, was severely wounded and compelled to leave the field. The command of these companies devolved on First Sergt. Francis E. Lacey, Company I, Second Infantry, who handled them well. In advancing to the fence, at which our line was to rest, the skirmishers were obliged to pass over a ridge completely commanded by the enemy's sharpshooters and battery posted to the left of the corn-field in front of the right of my line. When we appeared above its crest of the enemy opened with a heavy fire of case-shot and canister. The line did not waver, but rapidly moved to the fence. The right advanced beyond, however, before I could convey the order to them to halt at the fence, and by a well-directed fire compelled the enemy's cannoneers to leave their guns. At this juncture the fire from our own batteries compelled them to fall back to the fence, as their shells fell short. Lieutenant McLoughlin and Sergeant Lacey commanded the companies on the right. Sergeant Lacey was soon after wounded, and unwillingly compelled to leave the field. Our position was held until all the ammunition had been expended on the left and nearly all on the right. I reported our wants to Captain Dryer, and after the Seventeenth Michigan Regiment Volunteers arrived on our line, by his direction I assembled the battalion on the center files. The Fourteenth Infantry, First Battalion, came up on the right. I next quietly withdrew a short distance, halted the battalion under shelter to await a supply of ammunition. Before assembling the command, the enemy advanced a regiment to protect the withdrawal of their guns from the hill directly in front of our left. This regiment was driven back, but their object had been effected. About dusk I received an order to fall back to the bridge. On the way received another order to return to camp, which I did.

I must express my indebtedness to First Lieuts. J. W. Gray, Eleventh Infantry; A. W. Kroutinger, adjutant, Second Infantry; George S. Lauman, Tenth Infantry; Williams F. Drum and George H. McLoughlin, Second Infantry, for important assistance in handling successfully a very extended line of skirmishers. I would again bring to your notice First Sergt. F. E. Lacey as worthy a recommendation for a commission; also Sergt. Major William Fouck, Second Infantry. Those who most distinguished themselves for excellent behavior are First Sergt. Francis E. Lacey, Company I; First Sergt. Thomas Byrne, Company A; First Sergt. James Butler, Company C; Sergt. William Mitchell, Company D; First Sergt. Daniel W. Burke, Company B; First Sergt. Michael Dolan, Company E; First Sergt. John Trueman, Company F; Sergts. Martin Walsh and Timothy Hays, Company A. Private De Witt C. Bruke, Company C, was crippled slightly by a wound in the foot, but remained with the regiment until the close of the action. He is a brave soldier. Musician George Miller, Company G, seized a musket on the field and used it with good effect during the hottest part of the engagement.

Respectfully submitted.

J. S. POLAND,
First Lieutenant 2nd Infantry, Commanding Batt.2nd and 10th Infantry.
 
Now if you reverse the roles, Lee would have jumped all over that chance.
Question; Did Mc make the same error that Meade did in not bring his full full against the defeated Lee at the end ? Has Hill received the credit due his force for taking Lee out of the fire and rescuing the Confederate forces.If those troops had not arrived in time would Mc been able to hurt Lee .Do you know of a book which renders a near truth on that battle.
 
Question; Did Mc make the same error that Meade did in not bring his full full against the defeated Lee at the end ? Has Hill received the credit due his force for taking Lee out of the fire and rescuing the Confederate forces.If those troops had not arrived in time would Mc been able to hurt Lee .Do you know of a book which renders a near truth on that battle.

They both retreated after the battle... By no means it was a Union victory. AP Hill saved the day for the Confederates big time
 
Even assuming the rest of it is true, this is written without clarity. Porter said "I command the last reserve of the last Army of the Republic", but he did not say it was corps strength and that's because there was much less than a corps left. In fact, there were two brigades left (two of Morell's), everything else was doing things.
Which of Porter's troops participated in the battle and where did they fight? I'm just beginning to study this battle in depth the importance of which I think may be underrated, believe it or not.
 
Which of Porter's troops participated in the battle and where did they fight? I'm just beginning to study this battle in depth the importance of which I think may be underrated, believe it or not.
Okay, so Porter's 5th corps had eight brigades in three divisions (Morell 3, Sykes 3, Humphreys 2). At the beginning of the day Sykes was right up near the front, but things had gotten all mixed up in the force-march and so Morell was near the back of the column. Humphreys didn't arrive on the field until the day after the "battle" itself.

Counting off the brigades, we have:

Morell
Barnes' brigade - still in reserve around 1600 hours.
Griffin's brigade - sent to reinforce 6th Corps, later recalled, but marching time meant they were unavailable for some time (not becoming available again until after 1600 hours).
Stockton's brigade - with Griffin

Sykes
Buchanan's brigade - mostly engaged on the far side of the creek, a few regiments not. One of the regular brigades.
Lovell's brigade - ditto Buchanan.
Warren's brigade - very small and sent to Burnside, kept in local reserve. Not a regular brigade.

Humphreys
Not on the field.


Essentially Morell's division is the main reserve, and over half of it had been initially committed to the right. They were recalled again when things went wrong on Burnside's flank as well, of course.
This means that at 1600 hours (when Porter complained about having few troops) he had:

Sykes division supplying 4-5 unengaged combat battalions of regulars (i.e. about 1,000 effectives, a mix of units from several different regiments consolidated into battalions).
Morell's division supplying Barnes' brigade (i.e. about 1,700 effectives per Barnes' report).

So it's two brigades from different divisions, mea culpa.

The thing which confuses is that Morell's other two brigades - Griffin and Stockton - were committed but not engaged. They'd been sent north to reinforce the right flank, but didn't get there before the need came up for them elsewhere as well and McClellan recalled them. This is a time-consuming process.


Now, on the next day, Morell was sent south to Burnside as temporary reinforcement in case he was attacked - and Burnside promptly put them over the creek, meaning they weren't available. Humphreys was sent to Burnside to swap for Morell when he finally arrived, and Burnside took them without giving Morell back.


So, to make a long story short, only Sykes' Regulars actually fought at Antietam, but the rest of 5th Corps (which is to say, three normal brigades and one very small one) were still being used (mostly in the way reserves are used - commit them to an area or hold them in the centre). The fact that two (strong but green) of the seven brigades of the corps were off the field and one of them was tiny makes it seem like there was a lot of unfought manpower, but for all that it's a "corps" the actual effective strength of the units which didn't exchange fire was about 5,000-odd and the effective strength of the troops not sent to do a task on the day was about 2,700.


I know this isn't a very simple picture - that happens, sadly.
 
Okay, so Porter's 5th corps had eight brigades in three divisions (Morell 3, Sykes 3, Humphreys 2). At the beginning of the day Sykes was right up near the front, but things had gotten all mixed up in the force-march and so Morell was near the back of the column. Humphreys didn't arrive on the field until the day after the "battle" itself.

Counting off the brigades, we have:

Morell
Barnes' brigade - still in reserve around 1600 hours.
Griffin's brigade - sent to reinforce 6th Corps, later recalled, but marching time meant they were unavailable for some time (not becoming available again until after 1600 hours).
Stockton's brigade - with Griffin

Sykes
Buchanan's brigade - mostly engaged on the far side of the creek, a few regiments not. One of the regular brigades.
Lovell's brigade - ditto Buchanan.
Warren's brigade - very small and sent to Burnside, kept in local reserve. Not a regular brigade.

Humphreys
Not on the field.


Essentially Morell's division is the main reserve, and over half of it had been initially committed to the right. They were recalled again when things went wrong on Burnside's flank as well, of course.
This means that at 1600 hours (when Porter complained about having few troops) he had:

Sykes division supplying 4-5 unengaged combat battalions of regulars (i.e. about 1,000 effectives, a mix of units from several different regiments consolidated into battalions).
Morell's division supplying Barnes' brigade (i.e. about 1,700 effectives per Barnes' report).

So it's two brigades from different divisions, mea culpa.

The thing which confuses is that Morell's other two brigades - Griffin and Stockton - were committed but not engaged. They'd been sent north to reinforce the right flank, but didn't get there before the need came up for them elsewhere as well and McClellan recalled them. This is a time-consuming process.


Now, on the next day, Morell was sent south to Burnside as temporary reinforcement in case he was attacked - and Burnside promptly put them over the creek, meaning they weren't available. Humphreys was sent to Burnside to swap for Morell when he finally arrived, and Burnside took them without giving Morell back.


So, to make a long story short, only Sykes' Regulars actually fought at Antietam, but the rest of 5th Corps (which is to say, three normal brigades and one very small one) were still being used (mostly in the way reserves are used - commit them to an area or hold them in the centre). The fact that two (strong but green) of the seven brigades of the corps were off the field and one of them was tiny makes it seem like there was a lot of unfought manpower, but for all that it's a "corps" the actual effective strength of the units which didn't exchange fire was about 5,000-odd and the effective strength of the troops not sent to do a task on the day was about 2,700.


I know this isn't a very simple picture - that happens, sadly.
Thanks.
 
Question; Did Mc make the same error that Meade did in not bring his full full against the defeated Lee at the end ?
This is a tricky question. One of the reasons for it is the difficulty in determining whether Lee was "defeated" at the end, and another is what it would look like if McClellan did bring his full force.


At the end of the main day of fighting, McClellan essentially had a single solid line on the right (shielding the shattered right flank), about three brigades' worth in reserve in the centre, and Burnside on his left flank who'd been giving trouble making offensives all day.
The next day McClellan gets some reinforcements, but they're mostly exhausted from long marches, and his corps commanders (e.g. Sumner, Burnside) are objecting to renewed attack. The two options are a left-flank attack and a right-flank attack.

Burnside's in "need more troops just to defend" mode, and indeed absorbed Morell and Humphreys just to do this. Ordering an attack may well have resulted in more slowness, and there's both Jones and Hill on that flank anyway - it's fairly strong. (Humphreys is not a very strong division, they're all green.)

This means the remaining option is an all-out assault on the right, against the Dunker plateau, which is basically a replay of the morning assault on the 17th (and to get the same strength going in as on the morning of the 17th would mean getting Morell back, which might mean relieving Burnside of command).
To do this would basically mean everything available was going into the fight, and if it failed then McClellan is suddenly in big trouble. While Lee would indeed head back over the Potomac, if he conducted the moves he made historically he'd re-enter Maryland via Williamsport and McClellan wouldn't have the fresh troops (6th Corps historically) which blocked him.
 
Somebody please settle something for me if you can. I have so far been to five different printed sources and read five different sets of figures for the sizes of the two forces at Antietam. Tell me, please, how many troops each commander had and make me believe it. Please and thank you.
 
Somebody please settle something for me if you can. I have so far been to five different printed sources and read five different sets of figures for the sizes of the two forces at Antietam. Tell me, please, how many troops each commander had and make me believe it. Please and thank you.
All right. This is taken heavily from 67th's work (based on Carman), but hopefully I can summarize.

In all cases estimates are made of Effective strength, which is the lowest measure and is appropriate for Antietam due to all the straggling from forced-marches.


Confederates.

Using Carman as a base, and adding back in units Carman designated as "not engaged", plus catching a few other issues, 67th puts it as:

In Place 15th

  • "Evan's Division" - 3,111 infantry and 419 arty
  • DR Jones' Division - 3,810 infantry and
  • DH Hill - 7,773 infantry and 346 arty
= 14,694 infantry

On the 16th
  • 12,370 infantry (above)
  • Jackson: c. 1,600 infantry
  • Ewell: 4,401 infantry
  • Walker: 3,764 infantry
  • (both Ewell and Walker may straggle in more slowly)
= c. 24,449 infantry

Morning of the 17th

  • 24,449 infantry (above)
  • stragglers of Jackson: 2,830
  • McLaws: 2,823
  • RH Anderson: 5,000
= 35,112 infantry

Arriving during the 17th
  • (5-6,000 stragglers from the Harper's Ferry marches, no way to verify and not counted yet)
  • AP Hill: 3,914
= 39,026
deduct casualties to estimate total at end of the day = 36,702-9,919 = 26,783 (this overestimates as shattered units have lost cohesion)

Morning of the 18th
  • Deduct casualties in infantry: - 9,919 (undercount)
  • RH Anderson stragglers (say): 1,200
  • McLaws stragglers: 1,700
  • AP Hill stragglers: 1,300
= 32,810 (probably 2-3,000 less due to unaccounted for casualties)

Total Confederate Strength On the 17th

Infantry (inc. AP Hill): 39,026
Artillery (from Carman directly): 3,629
Cavalry (from Carman directly): 4,500*
Combatants on the 17th: 47,155 (42,454 exc/ AP Hill)

Total Confederate Strength On the 18th

Infantry: 32,810
Artillery (3,629-314, from Carman): 3,315
Cavalry (4,500 - 49, from Carman): 4,451
Combatants on the 18th: 40,576


The link provides breakdowns by division and in some cases by brigade.


Total infantry effectives over whole battle about 42,500, of which 39,000 were around on the 17th.


Union

This is spread over several posts because some corps are examined separately. (2nd and 9th corps get their

1st Corps
Official Strength: 14,856
Meade's statement of those carried into battle: ca. 9000
Approximate infantry strength: 8,619 (Carman)
Casualties: 2,590
Approximate infantry strength the morning of the 18th: 5,327 (Sears, p300)


2nd Corps
(here 67th looks regiment by regiment via Fox's regimental losses)


Richardson's Division

1st Brigade 1,107
2nd Brigade 1,354 (assume the duty men and the officers of the 88th NY cancel out)
3rd Brigade 1,173 (if a 25% deduction is taken for the regiments which appear to be PF the figure reduces to 845)
DIVISION INFANTRY: 3,306 (including reduction)

Sedgwick's Division

1st Brigade 1,701 PFD (but excluding the officers of 1st Minnesota). This is slightly higher than Carman, probably because he excluded the MN SS. A reasonable deduction of 25% for non-effectives suggests a combat strength of about 1,275.
2nd Brigade 1,635 (very rough)
3rd Brigade 1,946, deducting 25% for the PFD regiments leaves 1,664.
DIVISION INFANTRY: 4,584 (including reductions)

French's Division

1st Brigade 1,541 (and probably high, I believe the 132nd PA straggled badly and wasn't on the firing line in anything like the above strength)
2nd Brigade 1,315 (but highly questionable)
3rd Brigade 2,191 PFD, a 25% reduction would give them 1,643 engaged.
DIVISION INFANTRY: 4,499
Total infantry of 2nd Corps: 12,389
Add Artillery of 859 (Carman's figures): 13,248 (70.4% of present)


5th Corps
Official Strength: 12,939 (2 Divisions only)
Buchanan's brigade: 1,640 (Carman, but no supporting text could be found)
Lovell's brigade: 1,060 PFD consolidated into 4 battalions on the 20th (OR)
5th NY: less than 115 (effective strength at 2nd Bull Run minus casualties at said battle, battlefield marker)
10th NY: unknown
Morell: 5,407 PFD
Estimate: 6,990



6th Corps
Official Strength: 12,300 (of which 75-80% were combatants, B&L II, pp 595)
Force engaged at Crampton's Gap (Slocum's Div and Brooks' and Irwin's Bdes of Smith's Div): ca. 6,500 (of which 533 were casualties)
Strength of Smith's Division: ca. 4,500 (B&L II, pp 596)
PFD of Hancock's Bde (not included in the 6,500 engaged above, but in the strength of Smith's Division): 2,114, or ca. 1,600 combatants
Irwin's brigade: 1,684 (Carman)
Infantry Strength of 6th Corps: 8,324 (75% of present minus 901 for the artillery (figure from Carman)

9th Corps
Bottom line figure:
TOTAL INFANTRY: 8,357
Add in artillery at 979 (Carman): 9,336 (67.6%)

12th Corps: 10,126
Official Strength: 10,126
Carman: 7,239


Total infantry effectives over entire battle about 52,000 (bit less than this as this includes artillery for some corps)

In infantry terms the two sides were about even in veterans and McClellan also had about one extra corps of new troops who were not as good.



End of month post-Antietam Lee reported a strength of 52,500 PFD, and he'd suffered about 17,500 casualties (9,200 wounded by his own account and 8,500 prisoners or dead counted by McClellan) implying a pre-casualty PFD of 70,000 once casualties added back.
Immediately post-Antietam he reported 36,000 PFD, and the 16,000 increase is probably stragglers returning - this implies a strength of about 53,000 PFD immediately pre-Antietam given straggling, though not all of these would make it into the line any more than McClellan's did. 53,000 PFD implies about 42,000 Effectives, very roughly.


One other estimate made was to count regiments, which are roughly even in number on both sides. McClellan's regiments include some very fresh ones, which would be (1) bigger and (2) much less well trained, and apart from that the veteran regiments have largely been fighting one another and so have broadly similar average strength.


All this points to infantry veteran counts on both sides being about equal. The reason it's so hard to determine this is that both sides really raced to the battlefield and sometimes counts were taken at bad times (e.g. Jackson's men were counted 30 minutes after arriving and a day before going into the battle, IIRC) or not at all (some Union corps report their previous PFD as their total engaged, which is very unlikely.)
 
All right. This is taken heavily from 67th's work (based on Carman), but hopefully I can summarize.

In all cases estimates are made of Effective strength, which is the lowest measure and is appropriate for Antietam due to all the straggling from forced-marches.


Confederates.

Using Carman as a base, and adding back in units Carman designated as "not engaged", plus catching a few other issues, 67th puts it as:

In Place 15th

  • "Evan's Division" - 3,111 infantry and 419 arty
  • DR Jones' Division - 3,810 infantry and
  • DH Hill - 7,773 infantry and 346 arty
= 14,694 infantry

On the 16th
  • 12,370 infantry (above)
  • Jackson: c. 1,600 infantry
  • Ewell: 4,401 infantry
  • Walker: 3,764 infantry
  • (both Ewell and Walker may straggle in more slowly)
= c. 24,449 infantry

Morning of the 17th

  • 24,449 infantry (above)
  • stragglers of Jackson: 2,830
  • McLaws: 2,823
  • RH Anderson: 5,000
= 35,112 infantry

Arriving during the 17th
  • (5-6,000 stragglers from the Harper's Ferry marches, no way to verify and not counted yet)
  • AP Hill: 3,914
= 39,026
deduct casualties to estimate total at end of the day = 36,702-9,919 = 26,783 (this overestimates as shattered units have lost cohesion)

Morning of the 18th
  • Deduct casualties in infantry: - 9,919 (undercount)
  • RH Anderson stragglers (say): 1,200
  • McLaws stragglers: 1,700
  • AP Hill stragglers: 1,300
= 32,810 (probably 2-3,000 less due to unaccounted for casualties)

Total Confederate Strength On the 17th

Infantry (inc. AP Hill): 39,026
Artillery (from Carman directly): 3,629
Cavalry (from Carman directly): 4,500*
Combatants on the 17th: 47,155 (42,454 exc/ AP Hill)

Total Confederate Strength On the 18th

Infantry: 32,810
Artillery (3,629-314, from Carman): 3,315
Cavalry (4,500 - 49, from Carman): 4,451
Combatants on the 18th: 40,576


The link provides breakdowns by division and in some cases by brigade.


Total infantry effectives over whole battle about 42,500, of which 39,000 were around on the 17th.


Union

This is spread over several posts because some corps are examined separately. (2nd and 9th corps get their

1st Corps
Official Strength: 14,856
Meade's statement of those carried into battle: ca. 9000
Approximate infantry strength: 8,619 (Carman)
Casualties: 2,590
Approximate infantry strength the morning of the 18th: 5,327 (Sears, p300)


2nd Corps
(here 67th looks regiment by regiment via Fox's regimental losses)


Richardson's Division

1st Brigade 1,107
2nd Brigade 1,354 (assume the duty men and the officers of the 88th NY cancel out)
3rd Brigade 1,173 (if a 25% deduction is taken for the regiments which appear to be PF the figure reduces to 845)
DIVISION INFANTRY: 3,306 (including reduction)

Sedgwick's Division

1st Brigade 1,701 PFD (but excluding the officers of 1st Minnesota). This is slightly higher than Carman, probably because he excluded the MN SS. A reasonable deduction of 25% for non-effectives suggests a combat strength of about 1,275.
2nd Brigade 1,635 (very rough)
3rd Brigade 1,946, deducting 25% for the PFD regiments leaves 1,664.
DIVISION INFANTRY: 4,584 (including reductions)

French's Division

1st Brigade 1,541 (and probably high, I believe the 132nd PA straggled badly and wasn't on the firing line in anything like the above strength)
2nd Brigade 1,315 (but highly questionable)
3rd Brigade 2,191 PFD, a 25% reduction would give them 1,643 engaged.
DIVISION INFANTRY: 4,499
Total infantry of 2nd Corps: 12,389
Add Artillery of 859 (Carman's figures): 13,248 (70.4% of present)


5th Corps
Official Strength: 12,939 (2 Divisions only)
Buchanan's brigade: 1,640 (Carman, but no supporting text could be found)
Lovell's brigade: 1,060 PFD consolidated into 4 battalions on the 20th (OR)
5th NY: less than 115 (effective strength at 2nd Bull Run minus casualties at said battle, battlefield marker)
10th NY: unknown
Morell: 5,407 PFD
Estimate: 6,990



6th Corps
Official Strength: 12,300 (of which 75-80% were combatants, B&L II, pp 595)
Force engaged at Crampton's Gap (Slocum's Div and Brooks' and Irwin's Bdes of Smith's Div): ca. 6,500 (of which 533 were casualties)
Strength of Smith's Division: ca. 4,500 (B&L II, pp 596)
PFD of Hancock's Bde (not included in the 6,500 engaged above, but in the strength of Smith's Division): 2,114, or ca. 1,600 combatants
Irwin's brigade: 1,684 (Carman)
Infantry Strength of 6th Corps: 8,324 (75% of present minus 901 for the artillery (figure from Carman)

9th Corps
Bottom line figure:
TOTAL INFANTRY: 8,357
Add in artillery at 979 (Carman): 9,336 (67.6%)

12th Corps: 10,126
Official Strength: 10,126
Carman: 7,239


Total infantry effectives over entire battle about 52,000 (bit less than this as this includes artillery for some corps)

In infantry terms the two sides were about even in veterans and McClellan also had about one extra corps of new troops who were not as good.



End of month post-Antietam Lee reported a strength of 52,500 PFD, and he'd suffered about 17,500 casualties (9,200 wounded by his own account and 8,500 prisoners or dead counted by McClellan) implying a pre-casualty PFD of 70,000 once casualties added back.
Immediately post-Antietam he reported 36,000 PFD, and the 16,000 increase is probably stragglers returning - this implies a strength of about 53,000 PFD immediately pre-Antietam given straggling, though not all of these would make it into the line any more than McClellan's did. 53,000 PFD implies about 42,000 Effectives, very roughly.


One other estimate made was to count regiments, which are roughly even in number on both sides. McClellan's regiments include some very fresh ones, which would be (1) bigger and (2) much less well trained, and apart from that the veteran regiments have largely been fighting one another and so have broadly similar average strength.


All this points to infantry veteran counts on both sides being about equal. The reason it's so hard to determine this is that both sides really raced to the battlefield and sometimes counts were taken at bad times (e.g. Jackson's men were counted 30 minutes after arriving and a day before going into the battle, IIRC) or not at all (some Union corps report their previous PFD as their total engaged, which is very unlikely.)
I think I may believe it. Thanks.
 
Somebody please settle something for me if you can. I have so far been to five different printed sources and read five different sets of figures for the sizes of the two forces at Antietam. Tell me, please, how many troops each commander had and make me believe it. Please and thank you.

The honest answer is we really don't know. We can home in on rough ballpark figures using the best figures available.

For the Federals McClellan gives his last return in his report, which showed around 87,000 men. However, the extent of straggling was not really reported and according to Lincoln commenting afterwards some 30,000 of these men had straggled away during the advance and McClellan had only 60,000 actually at Antietam. We have figures for the effective strength of the 1st, 5th and 6th Corps from their commanders and they are 61%, 63% and 65% of their reported strength. If this were extended to the other corps then McClellan would have had ca. 55,000.

Taking accounts of the regimental commanders etc. reported in Carman gets to to a similar figure once you add in an estimate of the units not engaged.

An effective strength of 55,000 at Antietam I think is a reasonable estimate for McClellan. The two divisions that joined him on the 18th were probably around 8,000 effectives or so.

For the rebels there is a lot of attempts to lowball their strength to explain away Lee's failure. The lowest estimates that are creditable are around the 40,000 mark. There is a tendency to ignore just how many men actually joined Lee immediately after 2nd Manassas, which gave him around 76,000 PFD. Personally I think Lee had just over 40,000 effectives on the field on the field in the morning (42,454, but acknowledging that the figures for the cavalry may be exaggerated), and that he received 9-10,000 reinforcements in the form of AP Hill and stragglers during the 17th, and another 4,000 or so that night from stragglers.

I believe McClellan did have some advantage of numbers, but it was around 5:4. McClellan's edge in numbers is largely the result of the new militia joining him, and in terms of veterans both sides were probably equal. McClellan had an edge in artillery, and the rebels an edge in cavalry.
 
The honest answer is we really don't know. We can home in on rough ballpark figures using the best figures available.

For the Federals McClellan gives his last return in his report, which showed around 87,000 men. However, the extent of straggling was not really reported and according to Lincoln commenting afterwards some 30,000 of these men had straggled away during the advance and McClellan had only 60,000 actually at Antietam. We have figures for the effective strength of the 1st, 5th and 6th Corps from their commanders and they are 61%, 63% and 65% of their reported strength. If this were extended to the other corps then McClellan would have had ca. 55,000.

Taking accounts of the regimental commanders etc. reported in Carman gets to to a similar figure once you add in an estimate of the units not engaged.

An effective strength of 55,000 at Antietam I think is a reasonable estimate for McClellan. The two divisions that joined him on the 18th were probably around 8,000 effectives or so.

For the rebels there is a lot of attempts to lowball their strength to explain away Lee's failure. The lowest estimates that are creditable are around the 40,000 mark. There is a tendency to ignore just how many men actually joined Lee immediately after 2nd Manassas, which gave him around 76,000 PFD. Personally I think Lee had just over 40,000 effectives on the field on the field in the morning (42,454, but acknowledging that the figures for the cavalry may be exaggerated), and that he received 9-10,000 reinforcements in the form of AP Hill and stragglers during the 17th, and another 4,000 or so that night from stragglers.

I believe McClellan did have some advantage of numbers, but it was around 5:4. McClellan's edge in numbers is largely the result of the new militia joining him, and in terms of veterans both sides were probably equal. McClellan had an edge in artillery, and the rebels an edge in cavalry.
Thanks.
 
I don't recall so much confusion and disagreement about numbers in other battles. Many battles were preceding by marches which allowed for straggling and caused units to appear on the field sequentially.

Perhaps it has to do with conflicting narratives. One is that McClellan had significant numerical superiority and missed an opportunity to crush Lee through a combination of timidity and mismanagement. On the other hand, if numbers and combat power were roughly comparable, there is little to blame Mac for.
 
All right. This is taken heavily from 67th's work (based on Carman), but hopefully I can summarize.

In all cases estimates are made of Effective strength, which is the lowest measure and is appropriate for Antietam due to all the straggling from forced-marches.


Confederates.

Using Carman as a base, and adding back in units Carman designated as "not engaged", plus catching a few other issues, 67th puts it as:

In Place 15th

  • "Evan's Division" - 3,111 infantry and 419 arty
  • DR Jones' Division - 3,810 infantry and
  • DH Hill - 7,773 infantry and 346 arty
= 14,694 infantry

On the 16th
  • 12,370 infantry (above)
  • Jackson: c. 1,600 infantry
  • Ewell: 4,401 infantry
  • Walker: 3,764 infantry
  • (both Ewell and Walker may straggle in more slowly)
= c. 24,449 infantry

Morning of the 17th

  • 24,449 infantry (above)
  • stragglers of Jackson: 2,830
  • McLaws: 2,823
  • RH Anderson: 5,000
= 35,112 infantry

Arriving during the 17th
  • (5-6,000 stragglers from the Harper's Ferry marches, no way to verify and not counted yet)
  • AP Hill: 3,914
= 39,026
deduct casualties to estimate total at end of the day = 36,702-9,919 = 26,783 (this overestimates as shattered units have lost cohesion)

Morning of the 18th
  • Deduct casualties in infantry: - 9,919 (undercount)
  • RH Anderson stragglers (say): 1,200
  • McLaws stragglers: 1,700
  • AP Hill stragglers: 1,300
= 32,810 (probably 2-3,000 less due to unaccounted for casualties)

Total Confederate Strength On the 17th

Infantry (inc. AP Hill): 39,026
Artillery (from Carman directly): 3,629
Cavalry (from Carman directly): 4,500*
Combatants on the 17th: 47,155 (42,454 exc/ AP Hill)

Total Confederate Strength On the 18th

Infantry: 32,810
Artillery (3,629-314, from Carman): 3,315
Cavalry (4,500 - 49, from Carman): 4,451
Combatants on the 18th: 40,576


The link provides breakdowns by division and in some cases by brigade.


Total infantry effectives over whole battle about 42,500, of which 39,000 were around on the 17th.


Union

This is spread over several posts because some corps are examined separately. (2nd and 9th corps get their

1st Corps
Official Strength: 14,856
Meade's statement of those carried into battle: ca. 9000
Approximate infantry strength: 8,619 (Carman)
Casualties: 2,590
Approximate infantry strength the morning of the 18th: 5,327 (Sears, p300)


2nd Corps
(here 67th looks regiment by regiment via Fox's regimental losses)


Richardson's Division

1st Brigade 1,107
2nd Brigade 1,354 (assume the duty men and the officers of the 88th NY cancel out)
3rd Brigade 1,173 (if a 25% deduction is taken for the regiments which appear to be PF the figure reduces to 845)
DIVISION INFANTRY: 3,306 (including reduction)

Sedgwick's Division

1st Brigade 1,701 PFD (but excluding the officers of 1st Minnesota). This is slightly higher than Carman, probably because he excluded the MN SS. A reasonable deduction of 25% for non-effectives suggests a combat strength of about 1,275.
2nd Brigade 1,635 (very rough)
3rd Brigade 1,946, deducting 25% for the PFD regiments leaves 1,664.
DIVISION INFANTRY: 4,584 (including reductions)

French's Division

1st Brigade 1,541 (and probably high, I believe the 132nd PA straggled badly and wasn't on the firing line in anything like the above strength)
2nd Brigade 1,315 (but highly questionable)
3rd Brigade 2,191 PFD, a 25% reduction would give them 1,643 engaged.
DIVISION INFANTRY: 4,499
Total infantry of 2nd Corps: 12,389
Add Artillery of 859 (Carman's figures): 13,248 (70.4% of present)


5th Corps
Official Strength: 12,939 (2 Divisions only)
Buchanan's brigade: 1,640 (Carman, but no supporting text could be found)
Lovell's brigade: 1,060 PFD consolidated into 4 battalions on the 20th (OR)
5th NY: less than 115 (effective strength at 2nd Bull Run minus casualties at said battle, battlefield marker)
10th NY: unknown
Morell: 5,407 PFD
Estimate: 6,990



6th Corps
Official Strength: 12,300 (of which 75-80% were combatants, B&L II, pp 595)
Force engaged at Crampton's Gap (Slocum's Div and Brooks' and Irwin's Bdes of Smith's Div): ca. 6,500 (of which 533 were casualties)
Strength of Smith's Division: ca. 4,500 (B&L II, pp 596)
PFD of Hancock's Bde (not included in the 6,500 engaged above, but in the strength of Smith's Division): 2,114, or ca. 1,600 combatants
Irwin's brigade: 1,684 (Carman)
Infantry Strength of 6th Corps: 8,324 (75% of present minus 901 for the artillery (figure from Carman)

9th Corps
Bottom line figure:
TOTAL INFANTRY: 8,357
Add in artillery at 979 (Carman): 9,336 (67.6%)

12th Corps: 10,126
Official Strength: 10,126
Carman: 7,239


Total infantry effectives over entire battle about 52,000 (bit less than this as this includes artillery for some corps)

In infantry terms the two sides were about even in veterans and McClellan also had about one extra corps of new troops who were not as good.



End of month post-Antietam Lee reported a strength of 52,500 PFD, and he'd suffered about 17,500 casualties (9,200 wounded by his own account and 8,500 prisoners or dead counted by McClellan) implying a pre-casualty PFD of 70,000 once casualties added back.
Immediately post-Antietam he reported 36,000 PFD, and the 16,000 increase is probably stragglers returning - this implies a strength of about 53,000 PFD immediately pre-Antietam given straggling, though not all of these would make it into the line any more than McClellan's did. 53,000 PFD implies about 42,000 Effectives, very roughly.


One other estimate made was to count regiments, which are roughly even in number on both sides. McClellan's regiments include some very fresh ones, which would be (1) bigger and (2) much less well trained, and apart from that the veteran regiments have largely been fighting one another and so have broadly similar average strength.


All this points to infantry veteran counts on both sides being about equal. The reason it's so hard to determine this is that both sides really raced to the battlefield and sometimes counts were taken at bad times (e.g. Jackson's men were counted 30 minutes after arriving and a day before going into the battle, IIRC) or not at all (some Union corps report their previous PFD as their total engaged, which is very unlikely.)
I've been through the math now a zillion times and my numbers are very slightly higher than yours for both armies - about 43,500 for Lee (after Hill arrived) and about 61,000 for McClellan on September 17. We are on the same page.
 
I've been through the math now a zillion times and my numbers are very slightly higher than yours for both armies - about 43,500 for Lee (after Hill arrived) and about 61,000 for McClellan on September 17. We are on the same page.
That makes sense, assuming you're adding in the cav and arty. I was focused as far as possible on infantry.

As 67th notes, it does look like the Union had an advantage, but it's mostly fresh troops and not quite enough to compensate for the Confederate defensive posture. Came pretty close, though, and by a CEV calculation using your numbers:


McClellan had 61,000 and inflicted 17,500 (at 0.29 casualties per person)
Lee had 43,500 and inflicted 12,400 (at 0.285 casualties per person)

As Lee's army is smaller by about 40% it's this which represents how much better he did, for a final CEV value of 0.7 for McClellan (1.4 for Lee). It's really quite good for an attacking commander - Lee did about as well in the later parts of the Seven Days against McClellan, and much worse in the earlier parts (with entrenchments), which suggests the two were fairly close to evenly matched. By comparison Lee's CEV against Grant doesn't drop below 2.5 and at times gets as high as 11, and the only battle not against McClellan where Lee's CEV is worse than Antietam is Gettysburg (where Lee, not his opponent, is on the attack).

The view I tend to have of Antietam is that it was a closely fought battle where McClellan, while unable to drive home the decisive blow, nevertheless dealt Lee's army a major injury.
This probably explains why one Confederate general (Lee or Longstreet, can't remember which) said McClellan always struck the heaviest blows - and we should remember that the destruction of an army on the field was very rare in the Civil War, so McClellan not managing it hardly makes him a dunce!
 
Yes. I counted all arms. Sorry - it wasn't quite apples to apples.
No problem. The pervasive problem (dating back to the Lost Cause) has always been that the CS counts are a very low measure and their Union opponents are a higher one - so long as you're applying equal standards to North and to South then there shouldn't be any problems...

...except that some higher measures actually make the CSA look better per-man than they were, because in CS units a substantial fraction of non-combat duties were carried out by non-enlisted personnel (i.e. slaves and in some cases hired freedmen) while in US units enlisted men did all fatigue duties. This is one strong reason to use Effectives - it avoids this problem.
 
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