Around and around we go. So now it appears we agree that McClellan did NOT assign overall command at Glendale to Heintzelman. More moving of the goal posts. And yet again we're resorting to McClellan's unwritten "instructions" -
No. You want to see a written order to that effect that was survived. Most of these orders did not survive. We know that Heintzelman received orders because he says he did, and was told Sedgwick had been ordered to be his reserve.
There are questions, but Heintzelman definitely acted as a commander, albeit with the confusion caused by Sumner. Certainly Slocum etc. took orders from Heintzelman.
Indeed, technically McClellan doesn't need to say ought, because Heintzelman's seniority is enough. However, McClellan have Heintzelman a task, and assigned troops to him to perform it.
this set apparently anticipating Longstreet's attack, Jackson's inaction at White Oak, etc.,, meaning that placing McCall's battered division where he did with its predictable rout was all just a clever trap to be sprung on Longstreet.
This discussion has been about how McCall wasn't assigned to that position, and how he ended up there.
McCall didn't do a "predictable rout", but actually offered stubborn resistance. The fighting can be divided into the following phases:
1600: Jenkins advances to the nearby tree-line pushing back the 1st and 3rd Reserves who were out as skirmishers. He brings up his brigade battery to shell Cooper's Battery, but loses the firefight.
1645-1700 (Jenkins' first charge): Jenkins charges his brigade at Cooper's Battery, which is defended by the 1st and 9th Reserves. Cooper's battery was held and Jenkins repulsed in disorder.
1730-1800 (Kemper charges the German batteries): Longstreet started issuing orders to support Jenkins by attacking at 1700. Kemper went in south of Jenkins at the junction of McCall and Hooker, and charged 2 German 20 pounder batteries (from the arty res) supported by only 6 coys of the 12th Reserves. The Pennsylvanians fell back out of range and McCall sent the 5th, 8th and 13th Reserves down on Kemper's left, and Hooker sent Grover's brigade at Kemper's right. Realising he was now about to be in a Kesselschlacht, Kemper withdrew, taking 414 casualties in the process of whom 165 were captured by the 10th Reserves charging their rear.
1800-1815 (Jenkins' second charge): Jenkins rallied his brigade and, with the 9th and 10th Alabama of Wilcox's brigade, charged again. Cooper's Battery again was held. The two charges cost the Federals 258 casualties, and the Confederates lost 802. By this point, Dana's and Sully's brigades had returned and were behind McCall solidifying a second divisional line behind his.
1800-1830 (Branch and Strange go into the Kessel): Branch was on the right of Kemper, but was delayed. Strange (Pickett's Bde) followed Branch. Strange came up against Hooker's division, which they only engaged the skirmishers of Hooker before retreating. Branch got hammered by the 5th, 8th and 10th Reserves, and pushed them back, gaining 2 abandoned 20 pounders. Sedgwick's men countercharged and repulsed him. Strange came up against Hooker's division, and were repulsed.
1815-1845 (Wilcox's left charges Randol's battery): The left of Wilcox's brigade, the 8th and 11th Alabama, launched a charge at Randoll's battery, left of Cooper's battery and in Meade's front. They charged the 4th and 7th Reserves, and were initially repulsed. This was apparently not a planned attack, but the CO of the 8th Alabama, seeing the 9th and 10th charging with Jenkins, launched of his own accord. Running into 12 guns (as Thompson's battery also engaged) and 2 regts, the 8th Alabama was repulsed by artillery alone, and then the 11th. Parts of the 7th Reserves then countercharged, blocking the artillery's arcs. The Alabamans turn and received the 7th Reserves (capturing large numbers of them), and use the fleeing Pennsylvanians to mask another charge on the battery, which was overrun. However, out in the open the troops on the battery were shot down and forced to retreat for lack of supports.
1845-ca. 2000 (Pryor and Featherston demonstrate against Kearny, joined by Gregg): Pryor moved to within skirmishing range or Kearny's division and thought better of making a charge. Featherstone would form on his left, and later Gregg would move in to support. No assault was made on this front.
1930-ca. 2000 (Field captures Cooper's and Randol's Batteries): Ordered to the front about 1900, Field deployed his column where Jenkins had been. McCall had identified that his line here had been battered to non-existence, and had tried to get Berry to fill it. However, the martinet Kearny had quashed all the initiative in his subordinates and despite seeing the hole, no-one was authorised to move to fill it until Kearny approved. Kearny was eventually found and approved, but it was too late. Heintzelman had seen it, and had Taylor's brigade move there from Slocum. Caldwall's and Meagher's Brigade arrived from White Oak Swamp Bridge, and were placed behind Kearny. Palmer and Howe's brigades, under McClellan's orders, had marched to the crossroads and were behind Hooker. The entire position was solidifying. However, before Taylor could plug the gap, Field charged and overran the guns. He could not advance any further though as McCall's men supported by Sedgwick's right held the woodline. Field fell back to the next woodline, and JR Anderson came up and they solidified their position in the woodline with the abandoned guns between the lines. To the right of Field, Pender had advanced against the German batteries, but found Sedgwick's division defending it. To his right Archer found Hooker's division. It was dark and neither attacked. In the dark McCall blundered into Field's brigade and was captured.
End situation: The Federals had 16 guns in "no-man's land", the batteries of Cooper and Randol, two of Knieriem's and two others which had been spiked and abandoned. The Pennsylvania Reserves were shattered, and had given 100 yards of ground. Casualties by Federal division were roughly:
McCall: 1,118
Grover's Bde, Hooker: 195
Sedgwick: ca. 700
Kearny: ca. 800
Federal casualties = ca. 2,813
The only place where ground was lost was the clearing in front of Meade's line, where the reserves were pushed back 100 yards when no-one could authorise Berry moving into the gap, but was stabilised by Heintzelman moving Taylor down. To be fair, Kearny's division although not assaulted, did engage in a pretty brutal firefight, which puts one in mind of Albuhera.
The rebels had used 12 brigades to do this, and had taken the following casualties:
Jenkins: 589 (est, Gaines Mill not separated in OR, may be higher)
Kemper: 414
Wilcox: 468
Pickett (Hunton/ Strange): 228
Pryor: ca. 800 (862 at Gaines Mill and Glendale , but not really engaged at GM)
Featherstone : ca. 600 (667 at GM and G, as Pryor)
Longstreet's Casualties = ca. 3,099
Gregg: ca. 200 (partial estimate by battles, prorated over whole brigade)
Branch: ca. 450 (2 regts alone reported 206)
Pender: ca. 300 (The 22nd Va Bn reported 26 out of their 67 were at Glendale, prorated)
Field: ca. 300 (570 total, rough estimate based on others)
Archer and JR Anderson: negligible
AP Hill's Casualties = 1,250
Confederate Casualties = ca. 4,349
You might suggest that had Longstreet assaulted later, he could have done so in greater strength. This is of course true, but at the same time, the Federals would be stronger and better prepared. However, they didn't, and this is probably obvious from McClellan's position at the Crew House. Branch was in routine and cooking dinner. Longstreet had no plans to attack, and the whole attack developed as an accident; Jenkins charged Cooper's Battery, against orders, and Longstreet was wrongfooted and had to improvise an attack.
As to a "clever trap", no, but had Longstreet made a penetration he indeed would have been cut off and destroyed. You'll note a lot of the brigadiers were aware of this, and if they made headway against a position, they halted. They were fully aware that if they "broke through the lines", but were not well supported, they'd be enveloped and captured.
When I reach a conclusion that is at odds with what everybody else has concluded who has looked into the issue there are three options - (1) I'm just flat out smarter than everybody else (2) just maybe I took the wrong fork in the road and I'm fooling myself or (3) I just like inventing arguments. Have a nice day.
Argumentum ad populum.