Conventional thinking on this is all wrong. It's not that Iran would be stupid enough to use them offensively. No one's going to do that for obvious reasons. If they do, others will use theirs on Iran and the world may very well end for everyone. No one is going there. No one. That's the reason Russia will not use tactical nukes on Ukraine no matter how much Putin blusters. Pakistan and India, no matter how much they hate each other, won't use their nukes offensively. Future scenarios in such an exchange are too horrible to contemplate for everyone.
The same reason no one is going to give them to terrorist organizations. Fissionable material is traceable and the fallout, pun intended, would be exceptionally bad, i.e., the distinct possibility of getting nuked themselves. That's probably why it hasn't happened though there have been more than ample opportunity in the last 30 to 40 years.
What nukes do provide is the ultimate insurance for regime survival, be it Tehran, Pyongyang, Islamabad, New Delhi, etc. The ultimate "dead man's switch." And a counter weight to the US, Israel and other's ability to project conventional military power at will.
THAT'S the rub that's got the US, and particularly Israel, in a twist.
They couldn't beat on Iran, or any other nuclear armed state, whenever they feel like it. There's no way the attacks of the last several weeks would have occurred if Iran had deliverable nuclear weapons. And Israel and the US want to keep it that way. Whether a regime is bad, good or indifferent, if they feel there's credible existential threats, without nukes they're potentially under someone's thumb.
= new reply since forum marked as read