Arjun understood that he had no option but to fight the battle and requested Krishna to help him. Krishna agreed to be his charioteer, but said he would remain unarmed, without weapons. However as Arjun and his brothers began to lose in the face of some insidious treachery on the part of the opposition, Krishna realised that the world would be plunged into greater distress than what he had been born on earth to overcome and so he broke his pledge and used his ultimate weapon, a spinning disk like weapon, to decapitate the main adversary and ensure that Arjun and his brothers won the war.