The son of Dronacarya did not know the art of counteracting the weapon, and therefore Arjuna was asked to counteract it by the power of his own weapon

Expressions researched:
"The son of Dronacarya did not know the art of counteracting the weapon, and therefore Arjuna was asked to counteract it by the power of his own weapon"

Srimad-Bhagavatam

SB Canto 1

The son of Dronacarya did not know the art of counteracting the weapon, and therefore Arjuna was asked to counteract it by the power of his own weapon.

SB 1.7.28, Translation and Purport

O Arjuna, only another brahmāstra can counteract this weapon. Since you are expert in the military science, subdue this weapon's glare with the power of your own weapon.

For the atomic bombs there is no counterweapon to neutralize the effects. But by subtle science the action of a brahmāstra can be counteracted, and those who were expert in the military science in those days could counteract the brahmāstra. The son of Droṇācārya did not know the art of counteracting the weapon, and therefore Arjuna was asked to counteract it by the power of his own weapon.