It seems of the active great captains in WOT we've seen most of them in action, but I can't recall even seeing how Agelmar Jagad's mind works in regards to war type stuff. Was there anything in any of the books that hinted to his greatness?
2 Answers
No, not really.
In The Fires of Heaven Ch 27, Nuhel Dromond lists the great captains:
"Agelmar Jagad and Davram Bashere will no leave the Blight, I think, and Pedron Niall will surely no be of use to you. If Rodel Ituralde do be alive, he do be mired somewhere in what do remain of Arad Doman." He raised his thick thumb. "And that do leave Gareth Bryne."
They're listed again in Crossroads of Twilight, but not much is said about Agelmar except that he is a great captain. I'm hoping to see him in action in A Memory of Light.
Spoiler
You see him in action in A Memory of Light. All of the surviving great captains are given command of a battlefront; Jagad is sent to Tarwin's Gap.
Unfortunately:
Agelmar Jagad, along with all of the other great captains, is under Compulsion and purposefully engages in poor tactics. So you never get to see him at his best.