PURPORT

For the atomic bombs there is no counter weapon which can neutralise the effects, But by subtle science the action of similar Brahmastra could be counter acted and those who were expert in the military science in those days could also counter act the danger of atomic bomb like Brahmastram. The son of Dronacharya did not know the art of counter acting the weapon and therefore, Arjuna was asked to counter act it by the power of his own weapon.