I thought I saw the worst, dumbest medieval-ish battle in The Battle of Winterfell, but Battle of Eregion did remove it from the throne.
Ha! It wasn't even close to Winterfell bad.
War council at Winterfel.
Jon Snow: Alright. I need a fool proof plan guaranteed to kill off most of our army.
Tyrion: Well, you could stick your army outside of the fortified castle so that they get crushed in-between the army and the walls.
Jon Snow: Brilliant! We need more, though.
Sansa: What if you put the siege engines outside, too. Oh! And you can put them in front of the infantry to make them even more vulnerable.
Jon Snow: I don't know why you have been underappreciated in this show, Sansa. That was great.
Tyrion: Okay. I've been thinking. Stay with me here. What if... What if we took the Dothraki cavalry and stuck them in front of everyone in the pitch black and had them charge blindly out at an enemy that they have no idea of the exact location or when they are coming. It would of course be across uneven ground covered by snow and ice.
Melisandre: And I could come up right before they charge and light their swords on fire, destroying what little night vision they have, rendering them unable to see past the head of their horses as they charge!
Daenerys: Dragons!
Jon Snow: And I think that about closes this up.