When Krsna orders fighting, it must be concluded that violence is for supreme justice, and, as such, Arjuna should follow the instruction, knowing well that such violence, committed in the act of fighting for Krsna, is not violence at all because, at any rate, the man, or rather the soul, cannot be killed; so for the administration of justice, so-called violence is permitted. A surgical operation is not meant to kill the patient, but to cure him. Therefore the fighting to be executed by Arjuna at the instruction of Krsna is with full knowledge, so there is no possibility of sinful reaction.