SB 1.7 - The subtle nuclear weapon
When Aśvatthāmā saw that his horses were tired, he thought there was no alternative but to use brahmāstra. He touched water in sanctity and concentrated upon the chanting of the hymns for throwing nuclear weapons, although he did not know how to withdraw such weapons. Nuclear weapons were released thru subtle means by purification of sound – chanting hymns. A glaring light spread in all directions, and Arjuna thought his life was in danger. Fear and its accompanying need to defend are the core principles governing the material world. Everyone is afraid and lack security.
Arjuna prayed to Lord Kṛṣṇa addressing Him as the almighty Lord, whose energies are unlimited. Therefore, only Kṛṣṇa is competent to instill fearlessness in the hearts of His devotees. A devotee thus becomes fearless under the protection given by the Lord. Material existence is like a blazing fire in the forest, and thus everyone in the flames of material miseries can find the path of liberation in Kṛṣṇa alone. The guru is the mercy representative of the Lord, and thru his words, the guru can penetrate into the heart of the suffering person and inject transcendental knowledge, which alone can extinguish the fire of material existence.