Arjuna is a great warrior, fighter, and for a kṣatriya, to kill one is not very difficult task. The kṣatriyas are trained up, hunting. Hunting is allowed for the kṣatriyas. Just like medical practitioners, they are trained up how to practice surgical operation on dead body. It is not possible to, of course, for a gentleman, to push knife in someone's body. It is naturally very difficult thing. Rogues and thieves, they can stab. So as the doctors, medical men, surgeons are trained up to operate their knife on the dead body to see where are the nerves, similarly, kṣatriyas are also allowed for being trained how to kill.
Kṣatriya means . . . kṣata. Kṣata means injury; and tra means trāyate, saves. A kṣatriya has to save the citizen from being injured by others. He is called kṣatriya. Brāhmaṇa means one who knows Brahman, the supreme. So brāhmaṇa, kṣatriya, vaiśya, śūdra, these divisions are there according to quality. Guṇa-karma-vibhāgaśaḥ (BG 4.13). By guṇa. Guṇa means quality. And karma means actual operation of the guṇa.
So Arjuna was a kṣatriya, trained up by Droṇācārya how to kill. This is the . . . nonviolence is not the business of the kṣatriya. That is cowardice. They are taught how to become violent. Otherwise, they cannot rule over. Formerly, the judgment was given by the king, immediately finished. Not go to the court and wait for the judgment for ten years; in the meantime, everything is finished. Not like that. Anything, there was regularly, the king used to sit in his assembly, and all the criminals, culprits, they were judged by the king himself. Sometimes the king had to kill personally with the sword. Even in European countries, the royal orders were trained up.