Hmmm... That would seem to assume a rational and sane enemy...
That is not the case with Iran...
Iran's first nuke will probably be loaded into a container ship headed for Baltimore and detonated in the Chesapeake Bay near me...
The tidal wave would eliminate most of the east coast between Norfolk and NYC...
Retaliation would be 50-50 for occurring, but Iranians would hide deep inside their mountains just in case Harris-Pelousy hadn't dismantled our deterrents by then...
IAC. this is one of the reasons we keep our surfboards polished and ready... Larry Niven's and Jerry Pournelle's famous mote may show up only 1.5 -miles across the water from the wife & I...
The USSR, arguably, could cripple enough of our assets to make a first strike survivable (for them).
This, Iran cannot do. Not now, not ever.
Now, I'm one who doesn't buy the idea that Iran is led by crazy people who would welcome massive US nuclear retaliation for an attack against a soft target. I view the things that grow in Saudi Arabia as a much bigger threat.
But, I could obviously be wrong.>
But I stand by my original statement: "The acquisition of nuclear weapons by Iran is not a threat TO OUR NUCLEAR DETERRENT".