The nuclear bombing of Iran by a state would almost certainly be enough to precipitate the complete collapse of the NPT, which is already wobbly (the latest Review Conference ended in acrimony).
Subsequent nuclear weapons projects in erstwhile NPT NNWS could easily trigger a few regional wars, and from there the escalation to a global conflict is certainly possible.
Subsequent nuclear weapons projects in erstwhile NPT NNWS could easily trigger a few regional wars, and from there the escalation to a global conflict is certainly possible.