How Can Sri Krishna Tell Arjuna to Fight and Kill?

In the first verse, Dritarasra is asking his charioteer, Sanjaya, what's happening on the battlefield. Madhusudana supposes that Dritar asra is hoping and hoping that the Pandavas will choose this path of Dharma or reconcile somehow. How can Sri Krishna tell Arjuna to fight and kill when a hymsa, non-injury, is the main principle of Darma? And let's be very clear that this was not an ordinary battle. The term is Darma Yudha - which means righteous.