> And then again optimized thermonuclear weapons

Here in Blighty, during the early cold war we built fall-out shelters and equipped a civilian force with "Green Goddess" fire engines to enable them to extinguish fires from nuclear flash.

Yet this all stopped after development and adoption of the Hydrogen Bomb..... because unlike nuclear weapons (kT yield), trying to defend against thermonuclear weapons (MT yield) is pointless. This was a very real and honest defence policy.

https://en.wikipedia.org/wiki/Green_Goddess

[In the UK, some younger people may recognise the Green Goddess Fire engine because they were seen during fireman strikes].