I have some readers who are much older than I am, and this image should look familiar to anyone born before 1970.

This is the projected effects of nuclear fallout on the continental U.S. after what a Soviet nuclear strike would most likely have looked like. The average person assumes that nuclear war is about killing as many of the other side's civilians as possible. In reality the first two or three waves of targets are all strategic and military with the odd major city thrown in (Moscow, D.C., and New York would most certainly have fried in the first strike because of their economic and political value). But the Commies would have been far, far more interested in striking Grand Forks, ND and Omaha, NE than Chicago or Los Angeles. Their goal would have been to destroy as much of the U.S. retaliatory capacity as possible, which would lead them to the vast ICBM fields scattered across the Great Plains, Strategic Air Command in Omaha, and Cheyenne Mountain in rural Colorado, a.k.a. NORAD. Of course there is no possible way that the Soviets could have destroyed enough of our ability to wage war to prevent themselves from being destroyed in the return fire. The inverse was also true, which is often suggested as the reason there was no World War III. But I digress.
In targeting the vast empty middle of the U.S. a theoretical limited Soviet strike would seem to have spared a good portion of the population. Unfortunately those dozens of high-megaton explosions in the Plains would have generated enough fallout to irradiate everything and everyone downwind – which just happens to be about 75% of the American population. So people who were spared being fried in an explosion would get to enjoy a slow death from radiation poisoning. Unpleasant stuff to say the least. It may take historians a century or two to figure out A) how humanity came so close to letting it happen and B) how in the hell we managed to avoid it.
Now consider Iran.
We are well aware that Iran's leaders talk a good game, especially when the topic is Israel. They go on about "pushing Israel into the sea" and wiping the country from the face of the Earth and blah blah blah. And the global concern over the Iranian nuclear program is focused mostly on Israel. No one seriously thinks Iran could deliver a nuclear weapon to the U.S. or even much of Europe, recent short-range ballistic missile tests notwithstanding. But let's say Bill Kristol and all of his like-minded colleagues are right. Let's take the leap of faith and assume that Iran can enrich enough plutonium to assemble a working warhead. They can deliver it with some accuracy and they intend to use it against Israel.
Such an attack, if it hit a major city like Tel Aviv, would kill a vast number of Israelis; 50,000 would not be an unreasonable guess, not counting radiation poisoning. It would also irradiate about half of Iran when the winds carried all of the radioactive dust eastward. A larger-scale attack – several warheads hitting multiple sites in Israel – would only compound the problem. So one of three things must be true:
1. The Iranian leaders are suicidal fanatics who are willing to kill a good portion of their own people (not to mention all of their Muslim brothers in Jordan, Syria, and other nations which would be blanketed with fallout) to inflict some damage which fall far short of destroying Israel. Would it be a terrible loss in Israel? Of course. But factoring in the NATO response, which we must imagine would be swift and utterly devastating to Iran, they would be committing national suicide to inflict a couple hundred thousand deaths on Israel.
2. Iran does not understand what nuclear fallout and/or wind are.
3. This is all just bullshit posturing and bold talk from an unstable regime full of unstable people who realize that their proposed actions would fail to accomplish the goal of destroying Israel while bringing swift and utter destruction to all of Iran.
Accepting #1 requires one too many drinks off of the right-wing demonization-of-enemies Kool-Aid. To say that this is their strategy is just an updated version of "The bloodthirsty Commie will stop at nothing to kill every last freedom-loving American." Since #2 is highly dubious, that sort of narrows it down…