Dumbing it down

[lord of dor-lomin]

Could he have been stunned as he never even saw an enemy at his back, let alone being stabbed by the same?

Who in the world on a battlefield reacts to getting attacked by being "stunned"? Who's going to have that reaction?

I have a little something to say about this, because a while ago I got bit by a dog on the back of my leg. I wasn't expecting it but all of a sudden he up and bit me. Did I fall to my knees and sit there? No! Duh. That's the last thing your survival instinct tells you to do. Nobody would do that. Upon being bitten, I immediately whirled around and clubbed the dog with my fist, before I even knew what I was doing.

That's how people react to being attacked from behind (unless the attack is vicious enough to physically damage their brain or spine or something).

TWK's reaction is how people react from being stabbed at the base of the neck or hit in the head with a sludgehammer, which did not happen to him. There's no way you explain his reaction without a magical weapon.