Impetent people make impetent threats. The Jihsdis are good at that.
I think it’s possible for the b******* to bring in a handful of small nukes and detonte them. But it is hard to believe they would have access to 160—unless former USSR entities forked them up. Neither N. Korea or Iran has enough fissionsble material to fabricate that many bombs.
Although not absolutely airtight, yellow cake (uranium) mining is fairly closely monitored. Most of the material either has inherent or implanted source markers.
That said, vigilence continues to be the watchword.
It would be useful to identify and capture the letter writer. Then interrogate the letter writer under “rigorous” interrogation to hear what he/she has to say.
I think I read that both side has small nukes but their triggers have expiration dates.