@Knightia He should have fought it. If he had felt it's not possible, he should have incapacitated/ended himself. They are fighting a war of survival. If he can't be of use to the nation he's sworn to protect, the least he should do is to make sure he's not useful for the enemy. He's not like those villager scrubs, he's a professional soldier and one skillful enough to be an escort for a hero on a mission of extreme importance.
@Kaarme
Nonono, it would sadden the king if Arc really did end his life like what you suggested. In this manga, a good knight shouldn't make the king sad.