Given the worrying over nuclear Iran, it is timely to review the rules of nuclear proliferation.

NUCLEAR CRED

Otherwise insignificant nations and failed states gain credibility by shorting their own people to divert billions of dollars to acquiring a bomb. Take away that fact from Pakistan, and the United States would probably have reduced aid to such a de facto belligerent long ago. Without the ongoing appearance of possessing nukes, North Korea would probably earn about as much foreign aid as Chad or Niger. What makes France a world player, in a way that the much larger and richer Germany is not, is not just the burdens of German guilt, but also the fact of a nuclear France. The bomb sometimes achieves what even GDP, population, strategic location, or natural resources cannot.

MADNESS AS FORCE MULTIPLIER

Presumed madness is a force multiplier of nuclear capability, especially in an Islamic apocalyptic context. Under conventional nuclear deterrence, rough nuclear parity, and the assurance that neither side has a first-strike capability sufficient to render its opponent nuclearly impotent, prevent both wars and nuclear blackmail. But if a head of state can feign insanity, or, better yet, convincingly announce a wish for the apocalypse, then he can, in theory, circumvent some traditional rules of deterrence. An Iranian theocrat’s supposed willingness to use his sole nuclear weapon to wipe out tiny Israel — at the cost of losing 30 million Iranians from retaliation — yields a cheap way to obtain not just parity with Israel, but potentially a nuclear advantage.

In any given Middle Eastern crisis, a soon-to-be-nuclear Iran will always talk of the return of the hidden imam while threatening to repeat the Holocaust. By these means, it hopes to reap political concessions that its paltry array of nukes would not otherwise warrant. Acting as if one had nothing to lose is an advantage in nuclear poker — analogous to the supposedly prison-bound high-school dropout picking a fight with his graduating, Harvard-bound counterpart.

SORTA, KINDA NUCLEAR

All intelligence concerning the current status of the world’s nuclear club is inexact at best. Therefore, to achieve nuclear deterrence, it may not even be necessary for a rogue state to provide conclusive proof that it has nuclear weapons on hand and that they actually work.

Iraq might well never have been able to produce enough weapons-grade plutonium from its Osirak reactor to make a bomb, even had Israel not destroyed the plant in 1981. No matter: Had we known in 1991 that the reactor was intact and had been working for a decade, there is real doubt whether the United States would have dared to invade Iraq during the first Gulf War.

Moammar Qaddafi reportedly gave up his nuclear-weapons program for fear of meeting the same fate as Saddam Hussein. But he may have wrongly surmised, on the basis of our claim that we had invaded Iraq in part to stop Saddam’s WMD program, that the existence of such a program would have prompted a U.S. preemptive response. He might have been more accurate had he concluded that uncertainty about the status of his nuclear acquisition might have convinced the U.S. of the dangers of attacking such a potential nuclear power. Had Qaddafi instead accelerated work on his nuclear program from 2003 to 2011 — even falsely claiming at key intervals that he had a bomb — there is less likelihood that NATO would have bombed him out of power last year.

Syria, after the fall of Saddam, apparently better understood these realities and therefore was racing to enrich uranium and obtain one or two bombs. Israel destroyed its enrichment facility near Deir ez- Zor in 2007 when it was unequivocally clear that Syria was not yet nuclear. Note, as in the case of Saddam Hussein in 1981, that Bashar al-Assad did not retaliate against Israel in 2007 — apparently afraid to engage a nuclear Israel over a matter of nuclear weapons. Had the reactor not been bombed then, today, nearly five years later, Assad might well have been able to at least feign nuclear capability in a way that might have shielded him against foreign pressures.

To this day, we do not know whether North Korea has successfully detonated a nuclear bomb that is easily deliverable. But it does not matter; we need to know only that it has achieved some sort of nuclear reaction that suggests the ability to repeat it a few times. That fact prevents any sort of preemptive attack on a North Korean reactor, giving North Korea the sort of exemption that Iraq, Libya, and Syria never quite achieved.

NUCLEAR STOCKPILES ARE NOT ALL EQUAL

The United States, in well-meaning fashion, is supposedly considering unilaterally reducing its nuclear force, perhaps even well below the limits agreed on with the Russians. Rumors circulate that a few in the administration are pondering a more radical reduction, to 400 nukes or even fewer — about what China or India may possess.

If true, the logic is bewildering. There is little danger that the size of the U.S. nuclear stockpile per se will ever encourage an American preemptive nuclear strike. There is even less likelihood that terrorists will get their hands on American bombs. In a defense budget of over $600 billion, maintenance of our nuclear stockpiles is not an inordinate expense. Nor is there any evidence that spontaneously reducing stockpiles will encourage the same from others.

Most important, what is forgotten is the reason why the post–Cold War American stockpile is still so large. Unlike Russia or China, the U.S. has several key allies that are non-nuclear and whose security needs are met by our nuclear umbrella — in the sense that we pledge to defend them to the last nuke from any existential attack.

But there is more to it than that. Our allies themselves, unlike the rogue states we have been considering, have the capability to become nuclear overnight. The reason why Germany, Japan, South Korea, and Taiwan are not nuclear is not a matter of technology or finance; indeed, all four could this year alone create nukes as they do BMWs or Hondas. It is not just an American nuclear umbrella but rather a large American nuclear umbrella that assures such countries that they can rest secure without their own deterrent stockpiles.

In other words, if the Obama administration were to take us down to a few hundred bombs, it might send a signal to our allies that we could not possibly deter all their enemies simultaneously — and that they would be wiser to fend for themselves by obtaining their own nuclear arsenals. For each dozen bombs we retired, our allies might feel it necessary to make up the difference on their own.

DEMOCRATIC BOMBS

The danger is not the bomb per se, but rather who has it. Most of us do not worry about a democratic Britain, France, India, or Israel possessing nuclear weapons. The fright instead is over a Communist authoritarian China, an unhinged North Korea, an Islamist Pakistan, or an unstable Russia having nuclear weapons. Transparent democracies, in other words, are mostly reliable nuclear guardians; non-transparent autocracies are less so. Should Australia or Canada wish to acquire nuclear weapons, few privately would care; should Cuba or Zimbabwe, everyone publicly would care. It is always wise to limit the nuclear club, given the chance of accident or change of government; but wiser still to limit the non-democratic nuclear club.

PREEMPTIVE ATTACKS

There have been a handful of efforts to preempt and stop nuclear programs. Israel, as we have seen, has done it twice, against Iraq and Syria. America in 2003 claimed it was ensuring that Saddam did not have weapons of mass destruction. Note that all preemptive attacks so far have occurred in the Middle East — no surprise, given the rivalry of Israel, the Arab states, and Iran, the ubiquity of madmen, lots of cash, and 40 percent of the world’s oil.

What is strange is that Iran itself, the likely target of any future preemptive effort, was the first nation to attack another nation’s nuclear reactor. (Reports of Soviet efforts to target the Israeli reactor at Dimona during the Six-Day War are probably unfounded.) In 1980, Iran sent planes into Iraq to attack the Osirak facility, for fear that Saddam might develop a bomb during the Iraq-Iran War. That mostly failed mission damaged but did not destroy the facility, which was demolished a year later by the Israeli air force. For all the present Iranian talk of sovereignty, it was Iran that established the precedent that unhinged enemies cannot be allowed to have nuclear weapons. In the very first days of its war with Saddam Hussein it sought to ensure that Iraq would not go nuclear — perhaps with some help from Israeli intelligence. As a general rule, preemption against a nuclear facility is as immediately denounced as it is over time quietly appreciated — so long as the mission was successful.

IRAN

How do all these rules apply to Iran?

Tehran knows that it has enough natural gas for over a century of electrical-power production. It builds nuclear facilities only to gain prestige, expand its influence beyond what it otherwise would be, and engage in blackmail — always exaggerating the pace of its nuclear acquisition to convince potential preemptors that it may already have the bomb and therefore will retaliate in nuclear fashion. Likewise, it believes that the loonier and more suicidal it sounds, the more likely other countries are to grant concessions — successful states cannot afford to wager all that they have created on the likely hunch that a failed state like Iran is bluffing. If we cannot guarantee our allies deterrence from a nuclear Iran, then they will find a way to obtain it on their own — whether through preemption in the case of Israel or through nuclear acquisition in the case of the Gulf monarchies. Finally, Iranians understand the importance of knocking out an enemy’s nuclear facility — not least because they were the first ones to try it themselves.