Actually, he carried a MT yield version of Brahmastra, ala Brahmashirastra, which was used as a MAD. Without it, that story would have ended differently.
Nice to read Mahabharata...

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The Ashwatthama–Arjuna clash with the Brahmastra / Brahmashirastra is a perfect analogy for today’s ‘100 MT bomb’ talk. Two ultimate weapons facing off nearly destroyed the Earth, until wisdom intervened. Arjuna showed discipline and withdrew — Ashwatthama couldn’t, and his rage only brought tragedy to innocents. Likewise, massive doomsday bombs look impressive, but in practice they’re more dangerous to everyone, including their own side. Real strength lies in precision, restraint, and credibility — not in weapons that can’t be controlled once unleashed.
Building 100-MT bombs is like Ashwatthama firing a Brahmashirastra — impressive in rage, disastrous in reality, and no wiser than throwing fire in your own house.
Ashwatthama went for the Brahmashirastra — world-ending overkill. Arjun used Gandiv with precision. In today’s terms: why dream of 100-MT craters (Not to mention deadly fallout which does not respect national borders) when a precise missile does the job far better (and without burning down your own house)...
--- From Mahabharata, who might not be familiar with the whole story ..
(Reading the Mahabharata and understanding is quite useful - Brahmashirastra, which was considered catastrophic even then by epic standards...then .. see/read Vyas and other sages saying.."firing a Brahmashirastra in the middle of a crowded village — sure, it proves you have it.., but nobody sane thinks that’s the way to win"....Arjuna, with discipline and humility, withdrew his weapon as instructed..Ashwatthama, however, could not fully recall his, as he lacked the training ... Instead, he redirected it — tragically — in an attempt to wipe out the Pandava lineage. Krisna somehow saves Parikshit .. ityadi .... Moral was 'supreme weapons are a burden .. without discipline.. they cause devastation even to the wielder’s own side...)
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महायुद्धास्त्रविनियोगो हानिप्रधानः।
गाण्डीवसदृशं तु लक्ष्ये निशितम् एव श्रोत्रियः।।
Transliteration:
"Using a supreme weapon in anger brings mainly destruction. Like the Gandiv bow, a precise strike at the target alone achieves purpose safely."