Prabhupada's lecture - Śrīmad-Bhāgavatam 1.8.50 - Los Angeles, May 12, 1973
If somebody is aggressor, he must be killed immediately. Dharma-yuddha. Yudhiṣṭhira Mahārāja is thinking that "Although there was fight, the fight was between our own men, my brother, my nephews, my grandfather. So they are family members. I have killed them for my kingdom." He is thinking in that way. He is a pious man. Violence is required. We don't say nonviolence. Just as Caitanya Mahāprabhu, He gave us the instruction, tṛṇād api sunīcena taror api sahiṣṇunā: "One should be tolerant, forbearing like the tree, like the grass." Amāninā mānadena: "One should give respect to others. In this way one should chant Hare Kṛṣṇa mantra." Because in chanting Hare Kṛṣṇa mantra, there will be so many aggressors. The nature is so cruel. Just like Prahlāda Mahārāja, a five-years-old boy. His only fault was that he was chanting Hare Kṛṣṇa, and the father was aggressor, giving him trouble so many ways. So we must be prepared.
Therefore as there is danger... Suppose Caitanya Mahāprabhu has taught us that "Be tolerant," but not that where violence is required we should be tolerant. No. Just like while Nityānanda Prabhu was injured by Jagāi and Mādhāi, He wanted to immediately kill him. Similarly, nonviolence does not mean that in right causes also you will remain nonviolent. No. You do not attack anybody unnecessarily. You do not kill unnecessarily animal even, not even an ant. You should be nonviolent by your nature. But when there is aggression, there are enemies, the śāstra says, dharma-yuddha. That is dharma-yuddha.
So prajā-bhartur dharma-yuddhe vadho dviṣām. Dviṣām, envious. So they must be killed. But Yudhiṣṭhira Mahārāja was thinking in terms of fight between the family: their friends, their nephews, their grandfather. So he was thinking himself as culprit. But in dharma-yuddha... The Pāṇḍavas, they tried to settle the issue. Actually, the kingdom belonged to Mahārāja Yudhiṣṭhira. It was inheritance from his father, Pāṇḍu. But some way or other, they were cheated by the Kurus. They were sent to the forest. In the meantime they grabbed everything. And when they came back, so asked, "Give us some..., our ruling power,"so they would not give. "No. Without fight, we shall not give." So the Pāṇḍavas, even Kṛṣṇa tried their best to settle up the issue, but there was no settlement. So at that time, war was declared. That is dharma-yuddha. They tried to settle up the fight, but it was not possible. When it is not possible, then the last resort is to take to fighting. That is dharma-yuddha.