The brahmāstras are finer than the nuclear weapons. Aśvatthāmā discharged the brahmāstra simply to kill the Pāṇḍavas, namely the five brothers headed by Mahārāja Yudhiṣṭhira and their only grandson, who was lying within the womb of Uttarā. Therefore the brahmāstra, more effective and finer than the atomic weapons, was not as blind as the atomic bombs. When the atomic bombs are discharged they do not discriminate between the target and others. Mainly the atomic bombs do harm to the innocent because there is no control. The brahmāstra is not like that. It marks out the target and proceeds accordingly without harming the innocent.