I love this, but I do have to poke at the technicalities XD
technically a charge is a rushed advance towards an objective. It is not limited to offense but is typically used as a desperate strategy or in a scenario where there is no favorable outcome.
Two charging armies for instance, even when one shouts "retreat!" it is still a charge if they are advancing in a rushed manner towards an objective (such as safety)
That is why charge is used as a motivational spurring for an army. It is effectively saying "Victory is in our grasp!"
as another technicality, Sion could be referring to that he knows an enemy will not advance against him towards unfavorable terrain (the towers for instance)
Sion does not fear death, for he is already dead