Oh, point absolutely well-made, and taken, too. And I appreciate the discourse made in good faith, and the education for myself.
Well, while this dead horse is thoroughly flogged into pemmican here, I find that I am still at a loss...
three large armies afield in manuver, working around a general area, looking for a massed foe according to a plan. with latitude for individual discretion, what with communications being so difficult and all, but with the objective of putting the Sioux in a three way vise.
modern forensic examinations have unearthed huge amounts of new info in the last twenty years, and as the picture has become more complete, given rise to whole new theories of the whats, whys, and wherefores, some hinting at a little rehabilitation of the hapless fella's reputation.
So - as I understand it, mind - he divides his command and goes probing. Ok so far. And having located the Sioux, it wasn't like he could have lost them, but, reasonably, could have continued to keep contact with their whereabouts and sent word in order that the manuver take final shape. Nothing to be lost by standing off and keeping tabs, after all. Except a chance at personal glory.
But then, ahorse some distance out, he receives the reports, the intelligence, the recommendations of his own scouts, who say, in effect, "Ah, you might not want to go charging in down there..."
And it is in that moment that the die is cast, because damned if he doesn't go charging-in anyhow. And got his clock cleaned.
Why did he do that?
and no, he's not an idiot; he had "issues" of pride and self-blindness, a plague often seen in military, even all human, history...