Brahmāstra is the last weapon. Just like it is similar to modern nuclear weapon, brahmāstra. As by releasing nuclear weapon there is radiation, similarly, we have got description that when Aśvatthāmā released his brahmāstra, there was a big radiation, people were feeling very terrible heat. And then Kṛṣṇa informed that "This heat is due to the Aśvatthāmā's release of brahmāstra," and Arjuna was advised, "Counteract it." Now they do not know how to counteract this nuclear weapon. Formerly they knew. I throw one kind of weapon, and if you are expert, you can counteract it. Now they have discovered the nuclear weapon, but they have not yet discovered the counteraction. Fight means I show some expert fighting craft or experiencing; the opposite party must also show something better than that. That was fighting. And in this way, when one party fails, he's killed. And if he's killed, then war stops—no more war. This was the system.
So Aśvatthāmā was thinking of this brahmāstra. Astraṁ brahma-śiro mene ātma-trāṇaṁ dvijātmajaḥ. Hopelessly. So far, of course, I know that this nuclear weapon was already discovered by the German people, and Hitler, it is said that he did not use it. Because he knew it that "If I throw this nuclear weapon there will be devastation." So from this point it can be considered that he had some human consideration. So he's advertised very adversely, but if it is a true fact, then how he could have this human consideration that he did not throw the nuclear weapon? And this was taken by the Americans and it was thrown in Japan. That is the history so far we know. So anyway, as we have got experience, the nuclear weapon is very, very dangerous. Similarly, the brahmāstra is also very, very dangerous. And another weapon, they knew this art, śabda-bhedhī. Śabda-bhedhī means "If I throw some arrow, it will go to my enemy wherever he is. A little sound of the enemy will attract this weapon, and it is sure to kill my enemy." Śabda-bhedhī. There are many instances in Rāmāyaṇa, Mahābhārata. Śabda-bhedhī-bān.