Oddly, this discussion seems to have resolved itself into the issue of Custer. There are two books on Custer which are very good "Son of the Morning Star" and " A Good Year to Die". I have read the first and not the second. Custer made a fundamental mistake in dividing his command in the face of a superior force but, as I understand it, some of his subordinates, Reno and Benteen, hated him and did not come to his aid. His last message, to my memory was "Big Village, Come Quick, bring packs." This, I think to Reno, who was by now besieged on a hilltop. Custer was caught in the open and his force, about 250, was cut to pieces, shooting their horses for bulwarks and fighting in small groups with trap door Springfields that jammed. The Indians had repeaters. Custer was killed as well as his brother Tom, his cousin Boston and his brother in law Autie Reed. That ended what was called the Custer Gang in that army. Custer also did not wait for Crook who had also been driven back. Custer simply did not believe his intelligence and relied on tactics that worked. Charge in and the shock would do the rest. Still he was not a complete idiot. It takes a little bit more to be a total fool. If you look at Nathaniel Banks at the Red River, then you see planned stupidity. Banks abandoned his riverine support and marched up the road in a way which obviated his numerical superiority. Completely defeated by an inferior force, he had to fall back and lost even more on his retreat. Or, you can consider Burnside who managed three incredible defeats. Antietam, Fredericksburg and the Battle of the Crater. Of course, Burnside did have the integrity to tell his superiors that he was incompetent. They just did not believe it! Imagine, at the Crater, he "forgot" to remove the abatis in front of his position so that his own men got tangled up in his defenses.
I should also mention, in passing, Marshal Bazaine, who got shut up in Metz in 1870 after his ridiculous performance in Mexico. Regards, F.