At around 8:30 in the morning on Wednesday, January 11, while much of Tehran was snarled in its usual rush-hour traffic, a motorcyclist drew alongside a gray Peugeot and affixed a magnetic bomb to its exterior. The ensuing blast killed the car’s thirty-two-year-old passenger, Mostafa Ahmadi Roshan, a professor of chemistry and the deputy director of Iran’s premiere uranium enrichment facility. The assassin disappeared into traffic, and Roshan became the fifth Iranian nuclear scientist to die in violent or mysterious circumstances since 2007.

The attack was, in a sense, fairly typical of the covert war being waged against Iran’s nuclear program, a campaign that has included computer sabotage as well as the serial assassination of Iranian scientists. Even the manner of the killing was routine; Roshan was the third scientist to die from a magnet bomb slapped onto his car during a commute. But the timing of the chemist’s death—amid a series of diplomatic events that came fast and furious in January and February, each further complicating relations with Iran—had the effect of dramatizing how close this covert war may be to becoming an overt one.

On New Year’s Eve, eleven days before the bombing that killed Roshan, President Barack Obama enacted a new round of sanctions that essentially blacklisted Iran’s central bank by penalizing anyone who does business with it, a move designed to cripple the Islamic Republic’s ability to sell oil overseas. Iran responded by threatening to militarily shut down the Strait of Hormuz, the narrow shipping lane out of the Persian Gulf through which 20 percent of the world’s oil trade passes. On January 8, three days before the attack on Roshan, U.S. Defense Secretary Leon Panetta appeared on Face the Nation and reinforced America’s commitment to keep Iran from acquiring a nuclear weapon. Just in December, Panetta had emphasized the damaging consequences that war with Iran would bring, but now he stressed that Iranian development of a nuclear weapon would cross a “red line.” When the European Union announced its own sanctions of the Iranian central bank in late January, Iran redoubled its threat to block shipping lanes in the Strait of Hormuz. Panetta called this another “red line” that would provoke a military response from the U.S. February brought more posturing from Iran, along with two assassination attempts against Israelis living in New Delhi and Tbilisi that were widely attributed to Tehran.

All of this has played out against the unhelpful backdrop of American election-year politics. The Republican presidential candidates, with the exception of the antiwar libertarian Ron Paul, have seized on Iran as a possible winning issue and have tried to outdo each other in sounding bellicose about it. Mitt Romney has repeatedly discussed the use of military force as one way of fulfilling his promise that, if he is elected, Iran “will not have a nuclear weapon.” In short, both Democrats and Republicans have so ratcheted up their alarm about the possibility of an Iranian nuclear weapon that they are willing to commit to the extreme step of launching an offensive war—an act of aggression—to try to stop it.

Meanwhile, the Israeli government, which has led the way in talking up the danger of an Iranian bomb, represents a significant hazard outside Washington’s control. It was most likely the Israelis, for instance, who orchestrated the provocatively timed attack on Roshan. Defense Minister Ehud Barak recently dialed down the heat somewhat by saying that an Israeli decision to strike Iran was “far off.” But Prime Minister Benjamin Netanyahu, mindful of the U.S. electoral calendar and the possibility that Barack Obama might pull off a victory in November, may see a temporary opportunity to precipitate a conflict in which a preelection U.S. president would feel obliged to join in on Israel’s side.

Yet even without an Israeli decision to start a war, recent U.S., Iranian, and Israeli actions already constitute an escalation toward one. Rising tensions have increased the chance that even a minor incident, such as a seaborne encounter in the Persian Gulf, could spiral out of control. And Iran’s own covert actions—perhaps including the recent spate of car bombs targeting Israeli officials in India and Georgia and last year’s bizarre alleged plot to blow up a restaurant in Washington, D.C., and kill the Saudi ambassador—feed even more hostility from the U.S. and Israel, escalating further the risk of open conflict.

Thus we find ourselves at a strange pass. Those in the United States who genuinely yearn for war are still a neoconservative minority. But the danger that war might break out—and that the hawks will get their way—has nonetheless become substantial. The U.S. has just withdrawn the last troops from one Middle Eastern country where it fought a highly costly war of choice with a rationale involving weapons of mass destruction. Now we find ourselves on the precipice of yet another such war—almost purely because the acceptable range of opinion on Iran has narrowed and ossified around the “sensible” idea that all options must be pursued to prevent the country from acquiring nuclear weapons.

Given the momentousness of such an endeavor and how much prominence the Iranian nuclear issue has been given, one might think that talk about exercising the military option would be backed up by extensive analysis of the threat in question and the different ways of responding to it. But it isn’t. Strip away the bellicosity and political rhetoric, and what one finds is not rigorous analysis but a mixture of fear, fanciful speculation, and crude stereotyping. There are indeed good reasons to oppose Iranian acquisition of nuclear weapons, and likewise many steps the United States and the international community can and should take to try to avoid that eventuality. But an Iran with a bomb would not be anywhere near as dangerous as most people assume, and a war to try to stop it from acquiring one would be less successful, and far more costly, than most people imagine.

What difference would it make to Iran’s behavior and influence if the country had a bomb? Even among those who believe that war with the Islamic Republic would be a bad idea, this question has been subjected to precious little careful analysis. The notion that a nuclear weapon would turn Iran into a significantly more dangerous actor that would imperil U.S. interests has become conventional wisdom, and it gets repeated so often by so many diverse commentators that it seldom, if ever, is questioned. Hardly anyone debating policy on Iran asks exactly why a nuclear-armed Iran would be so dangerous. What passes for an answer to that question takes two forms: one simple, and another that sounds more sophisticated.

The simple argument is that Iranian leaders supposedly don’t think like the rest of us: they are religious fanatics who value martyrdom more than life, cannot be counted on to act rationally, and therefore cannot be deterred. On the campaign trail Rick Santorum has been among the most vocal in propounding this notion, asserting that Iran is ruled by the “equivalent of al-Qaeda,” that its “theology teaches” that its objective is to “create a calamity,” that it believes “the afterlife is better than this life,” and that its “principal virtue” is martyrdom. Newt Gingrich speaks in a similar vein about how Iranian leaders are suicidal jihadists, and says “it’s impossible to deter them.”

The trouble with this image of Iran is that it does not reflect actual Iranian behavior. More than three decades of history demonstrate that the Islamic Republic’s rulers, like most rulers elsewhere, are overwhelmingly concerned with preserving their regime and their power—in this life, not some future one. They are no more likely to let theological imperatives lead them into self-destructive behavior than other leaders whose religious faiths envision an afterlife. Iranian rulers may have a history of valorizing martyrdom—as they did when sending young militiamen to their deaths in near-hopeless attacks during the Iran-Iraq War in the 1980s—but they have never given any indication of wanting to become martyrs themselves. In fact, the Islamic Republic’s conduct beyond its borders has been characterized by caution. Even the most seemingly ruthless Iranian behavior has been motivated by specific, immediate concerns of regime survival. The government assassinated exiled Iranian dissidents in Europe in the 1980s and ’90s, for example, because it saw them as a counterrevolutionary threat. The assassinations ended when they started inflicting too much damage on Iran’s relations with European governments. Iran’s rulers are constantly balancing a very worldly set of strategic interests. The principles of deterrence are not invalid just because the party to be deterred wears a turban and a beard.

If the stereotyped image of Iranian leaders had real basis in fact, we would see more aggressive and brash Iranian behavior in the Middle East than we have. Some have pointed to the Iranian willingness to incur heavy losses in continuing the Iran-Iraq War. But that was a response to Saddam Hussein’s invasion of the Iranian homeland, not some bellicose venture beyond Iran’s borders. And even that war ended with Ayatollah Khomeini deciding that the “poison” of agreeing to a cease-fire was better than the alternative. (He even described the cease- fire as “God’s will”—so much for the notion that the Iranians’ God always pushes them toward violence and martyrdom.)

Throughout history, it has always been worrisome when a revolutionary regime with ruthless and lethal internal practices moves to acquire a nuclear weapon. But it is worth remembering that we have contended with far more troubling examples of this phenomenon than Iran. Millions died from forced famine and purges in Stalin’s Soviet Union, and tens of millions perished during the Great Leap Forward in Mao Tse-tung’s China. China’s development of a nuclear weapon (it tested its first one in 1964) seemed all the more alarming at the time because of Mao’s openly professed belief that his country could lose half its population in a nuclear war and still come out victorious over capitalism. But deterrence with China has endured for half a century, even during the chaos and fanaticism of Mao’s Cultural Revolution. A few years after China got the bomb, Richard Nixon built his global strategy around engagement with Beijing.

The more sophisticated-sounding argument about the supposed dangers of an Iranian nuclear weapon—one heard less from politicians than from policy-debating

intelligentsia—accepts that Iranian leaders are not suicidal but contends that the mere possession of such a weapon would make Tehran more aggressive in its region. A dominant feature of this mode of argument is “worst-casing,” as exemplified by a pro-war article by Matthew Kroenig in a recent issue of Foreign Affairs. Kroenig’s case rests on speculation after speculation about what mischief Iran “could” commit in the Middle East, with almost no attention to whether Iran has any reason to do those things, and thus to whether it ever would be likely to do them.

Kroenig includes among his “coulds” a scary possibility that also served as a selling point of the Iraq War: the thought of a regime giving nuclear weapons or materials to a terrorist group. Nothing is said about why Iran or any other regime ever would have an incentive to do this. In fact, Tehran would have strong reasons not to do it. Why would it want to lose control over a commodity that is scarce as well as dangerous? And how would it achieve deniability regarding its role in what the group subsequently did with the stuff? No regime in the history of the nuclear age has ever been known to transfer nuclear material to a nonstate group. That history includes the Cold War, when the USSR had both a huge nuclear arsenal and patronage relationships with a long list of radical and revolutionary clients. As for deniability, Iranian leaders have only to listen to rhetoric coming out of the United States to know that their regime would immediately be a suspect in any terrorist incidents involving a nuclear weapon.

The more sophisticated-sounding argument links Iran with sundry forms of objectionable behavior, either real or hypothetical, without explaining what difference the possession of a nuclear weapon would make. Perhaps the most extensive effort to catalog what a nuclear-armed Iran might do outside its borders is a monograph published last year by Ash Jain of the Washington Institute for Near East Policy. Jain’s inventory of possible Iranian nastiness is comprehensive, ranging from strong-arming Persian Gulf states to expanding a strategic relationship with Hugo Chávez’s Venezuela. But nowhere is there an explanation of how Iran’s calculations—or anyone else’s— would change with the introduction of a nuclear weapon. The most that Jain can offer is to assert repeatedly that because Iran would be “shielded by a nuclear weapons capability,” it might do some of these things. We never get an explanation of how, exactly, such a shield would work. Instead there is only a vague sense that a nuclear weapon would lead Iran to feel its oats.

Analysis on this subject need not be so vague. A rich body of doctrine was developed during the Cold War to outline the strategic differences that nuclear weapons do and do not make, and what they can and cannot achieve for those who possess them. Such weapons are most useful in deterring aggression against one’s own country, which is probably the main reason the Iranian regime is interested in developing them. They are much less useful in “shielding” aggressive behavior outside one’s borders, except in certain geopolitical situations in which their use becomes plausible.

The Pakistani-Indian conflict may be such a situation. Pakistan’s nuclear arsenal may have enabled it to engage in riskier behavior in Kashmir than it otherwise would attempt, because nuclear weapons help to deter Pakistan’s ultimate nightmare: an assault by the militarily superior India, which could slice Pakistan in two and perhaps destroy it completely. But if you try to apply that logic to Iran, no one is playing the role of India. Iran has its own tensions and rivalries with its neighbors— including Iraq, Saudi Arabia, other states on the Persian Gulf, and Pakistan. But none of these pose the kind of existential threat that Pakistan sees coming from India. Moreover, none of the current disputes between Iran and its neighbors (such as the one over ownership of some small islands also claimed by the United Arab Emirates) come close to possessing the nation-defining significance that the Kashmir conflict poses for both Pakistan and India.

Nuclear weapons matter insofar as there is a credible possibility that they will be used. This credibility is hard to achieve, however, in anything short of circumstances that might involve the destruction of one’s nation. In the case of Iran, there would need to be some specific aggressive or subversive act that Tehran is holding back from performing now for fear of retaliation—from the Americans, the Israelis, the Saudis, or someone else. Further, in order for Iran to neutralize the threat of retaliation, the desired act of mischief would have to be so important to Tehran that it could credibly threaten to escalate the matter to the level of nuclear war. Proponents of a war with Iran have been unable to provide an example of a scenario that meets these criteria, however. The impact of Iran possessing a bomb is therefore far less dire than the alarmist conventional wisdom suggests.

To be sure, the world would be a better place without an Iranian nuclear weapon. An Iranian bomb would be a setback for the global nuclear nonproliferation regime, for example, and the arms control community is legitimately concerned about it. It would also raise the possibility that other regional states, such as Saudi Arabia or Egypt, might be more inclined to try to acquire nuclear weapons as well. But that raises the question of why these states have not already done so, despite decades of facing both Israel’s nuclear force and tensions with Iran. Ever since John F. Kennedy mused that there might be fifteen to twenty-five states with nuclear weapons by the 1970s, estimates of the pace of proliferation—like estimates of the pace of Iran’s nuclear program—have usually been too high.

Furthermore, it’s not clear that any of this would cause substantial and direct damage to U.S. interests. Indeed, the alarmists offer more inconsistent arguments when discussing the dynamics of a Middle East in which rivals of Iran acquire their own nuclear weapons. If, as the alarmists project, nuclear weapons would appreciably increase Iranian influence in the region, why wouldn’t further nuclear proliferation—which the alarmists also project—negate this effect by bestowing a comparable benefit on the rivals?

In the absence of further proliferation among Iran’s rivals, there is a chance that Iran would be marginally bolder if it possessed a nuclear weapon—and that the United States and other countries in the Middle East would be correspondingly less bold. Perceptions of strength do matter. But two further observations are important. First, once concrete confrontations occur, strategic realities trump perceptions. One of the conjectures in Jain’s monograph, for instance, is that Hezbollah and Hamas might become emboldened if Iran extended a nuclear umbrella over them. But in the face of Israel’s formidable nuclear superiority, would Iranian leaders really be willing to risk Tehran to save Gaza? The Iranians could not get anyone to believe such a thing.

Second, one must ultimately ask whether the conjectured consequences of an Iranian bomb would be worse than a war with Iran. The conjectures are just that. They are not concrete, not based on nuclear doctrine or rigorous analysis, and not even likely. They are worst-case speculations, and not adequate justifications for going to war.

When the debate turns from discussing the consequences that would flow from Iran’s acquisition of a nuclear weapon to discussing the consequences of a U.S. military attack on Iran, the mode of argument used by proponents of an attack changes entirely. Instead of the worst case, the emphasis is now on the best case. This “best-casing” often rests on the assumption that military action would take the form of a confined, surgical use of air power to take out Iran’s nuclear facilities. But the dispersed nature of the target and the U.S. military’s operational requirements (including the suppression of Iranian air defenses) would make this a major assault. It would be the start of a war with Iran. As Richard Betts remarks in his recent book about the American use of military force, anyone who hears talk about a surgical strike should get a second opinion.

If the kind of worst-casing that war proponents apply to the implications of a nuclear Iran were applied to this question, the ramifications would be seen as catastrophic: we would be hearing about a regional conflagration involving multiple U.S. allies, sucking in U.S. forces far beyond the initial assault. When the Brookings Institution ran a war-games simulation a couple of years ago, an Israeli strike on Iranian nuclear facilities escalated into a region-wide crisis in which Iranian missiles were raining down on Saudi Arabia as well as Israel, and Tehran launched a worldwide terrorist campaign against U.S. interests.

No one knows what the full ramifications of such a war with Iran would be, and that is the main problem with any proposal to use military force against the Iranian nuclear program. But the negative consequences for U.S. interests are likely to be severe. In December, Secretary Panetta identified some of those consequences when he warned of the dangers of war: increased domestic support for the Iranian regime; violent Iranian retaliation against U.S. ships and military bases; “severe” economic consequences; and, perhaps, escalation that “could consume the Middle East in a confrontation and a conflict that we would regret.”

Surely, Iran would strike back, in ways and places of its own choosing. That should not be surprising; it is what Americans would do if their own homeland were attacked. Proponents of an attack and some Israeli officials offer a more sanguine prediction of the Iranian response, and this is where their image of Iran becomes most inconsistent. According to this optimistic view, the same regime that cannot be trusted with a nuclear weapon because it is recklessly aggressive and prone to cause regional havoc would suddenly become, once attacked, a model of calm and caution, easily deterred by the threat of further attacks. History and human behavior strongly suggest, however, that any change in Iranian conduct would be exactly the opposite—that as with the Iran-Iraq War, an attack on the Iranian homeland would be the one scenario that would motivate Iran to respond zealously. Iran’s specific responses would probably include terrorism through its own agents as well as proxy groups, other violent reprisals against U.S. forces in the region, and disruption of the exports of other oil producers.

An armed attack on Iran would be an immediate political gift to Iranian hard-liners, who are nourished by confrontation with the West, and with the United States in particular. Armed attack by a foreign power traditionally produces a rally-round-the-flag effect that benefits whatever regime is in power. Last year a spokesperson for the opposition Green Movement in Iran said the current regime “would really like for someone” to bomb the nuclear facilities because “this would then increase nationalism and the regime would gather everyone and all the political parties around itself.” Over the longer term, an attack would poison relations between the United States and generations of Iranians. It would become an even more prominent and lasting grievance than the U.S.-engineered overthrow of Prime Minister Mohammad Mosaddeq in 1953 or the accidental shooting down of an Iranian airliner over the Persian Gulf in 1988. American war proponents who optimistically hope that an attack would somehow stir the Iranian political pot in a way that would undermine the current clerical regime are likely to be disappointed. Even if political change in Iran occurred, any new regime would be responsive to a populace that has more reason than ever to be hostile to the United States.

Regional political consequences would include deepened anger at the United States for what would be seen as unprovoked killing of Muslims—with everything such anger entails in terms of stimulating more extremist violence against Americans. The emotional gap between Persians and Arabs would lessen, as would the isolation of Iran from other states in the region. Contrary to a common misconception, the Persian Gulf Arabs do not want a U.S. war with Iran, notwithstanding their own concerns about their neighbor to the north. The misconception stems mainly from misinterpretation of a Saudi comment in a leaked cable about “cutting off the head of the snake.” Saudi and other Gulf Arab officials have repeatedly indicated that while they look to U.S. leadership in containing Iranian influence, they do not favor an armed attack. The former Saudi intelligence chief and ambassador to the United States, Prince Turki Al Faisal, recently stated, “It is very clear that a military strike against Iran will be catastrophic in its consequences, not just on us but the world in general.”

Then there are the economic consequences that would stem from a U.S.-Iranian war, which are incalculable but likely to be immense. Given how oil markets and shipping insurance work, the impact on oil prices of any armed conflict in the vicinity of the Persian Gulf would be out of proportion to the amount of oil shipments directly interdicted, even if the U.S. Navy largely succeeded in keeping the Strait of Hormuz open. And given the current fragility of Western economies, the full economic cost of a war would likewise be out of proportion to the direct effect on energy prices, a sudden rise in which might push the U.S. economy back into recession.

In return for all of these harmful effects, an attack on Iran would not even achieve the objective of ensuring a nuclear- weapons-free Iran. Only a ground invasion and occupation could hope to accomplish that, and not even the most fervent anti-Iranian hawks are talking about that kind of enormous undertaking. Panetta’s estimate that an aerial assault would set back the Iranian nuclear program by only one or two years is in line with many other assessments. Meanwhile, an attack would provide the strongest possible incentive for Iran to move forward rapidly in developing a nuclear weapon, in the hope of achieving a deterrent to future attacks sooner rather than later. That is how Iraq reacted when Israel bombed its nuclear reactor in 1981. Any prospect of keeping the bomb out of Iranian hands would require still more attacks a couple of years hence. This would mean implementing the Israeli concept of periodically “mowing the lawn”—a prescription for unending U.S. involvement in warfare in the Middle East.

“There’s only one thing worse than military action against Iran,” Senator John McCain has said, “and that is a nuclear-armed Iran.” But any careful look at the balance sheet on this issue yields the opposite conclusion. Military action against Iran would have consequences far worse than a nuclear-armed Iran.

War or a world with an Iranian bomb are not the only alternatives. The judgment of the U.S. intelligence community, as voiced publicly by Director of National Intelligence James Clapper, is that Iran is retaining the option to build nuclear weapons but has not yet decided to do so. Much diplomatic ground has yet to be explored in searching for a formula that would permit Iran to have a peaceful nuclear program with enough inspections and other safeguards to assuage Western concerns about diversion of nuclear material to military use. As Trita Parsi reports in a recent book, the Obama administration’s brief fling at diplomacy in 2009 was, in the words of a senior State Department official, “a gamble on a single roll of the dice.” Now the administration, having seen how stridency toward Iran has threatened to get out of hand, seems willing to try diplomacy again in talks with Iran that will also include Britain, France, Germany, Russia, and China.

The sanctions on Iran have probably contributed to Tehran’s willingness to negotiate as well. Unless carefully wedded to diplomacy, however, sanctions risk being a counterproductive demonstration of Western hostility. Besides being serious about searching for a mutually acceptable formula of inspections and procedures that would safeguard against Iranian use of nuclear material for military purposes (and which may need to permit some Iranian enrichment of uranium), Western negotiators need to persuade the Iranians that concessions on their part will lead to the lifting of sanctions. This may be hard to do, partly because the legislation that imposes U.S. sanctions on Iran mentions human rights and other issues besides the nuclear program, and partly because many U.S. hawks openly regard sanctions only as a tool to promote regime change or as a necessary step toward being able to say that “diplomacy and sanctions have failed,” and thus launching a war is the only option left. The challenge for the Obama administration is to persuade Tehran that this attitude does not reflect official policy.

Why would anyone, weighing all the costs and risks on each side of this issue, even consider starting a war with Iran? The short answer is that neocon habits die hard. It might seem that the recent experience of the Iraq War should have entirely discredited such proclivities, or at least dampened policymakers’ inclination to listen to those who have them. But the war in Iraq may have instead inured the American public to the extreme measure of an offensive war, at least when it involves weapons of mass destruction and loathsome Middle Eastern regimes.

The Iranian government has provided good reason for Americans to loathe it, from its harsh suppression of the Green Movement to the anti-Semitic rants and other outrageous statements of President Mahmoud Ahmadinejad. Unfortunately the belligerent rhetoric in Iran feeds belligerent rhetoric in the United States and vice versa, in a process that yields beliefs on each side that go beyond the reality on the other side. The demonization of Iran in American discourse has gone on for so long that even unsupported common wisdom is taken for granted. The excesses of the Republican primary campaign have contributed to the pattern. Michele Bachmann, for example, may be out of the race, but when she stated that the Iranian president “has said that if he has a nuclear weapon he will use it to wipe Israel off the face of the Earth,” it was the sort of untruth that has tended to stick in the current climate (never mind that Iran claims it doesn’t even want nuclear weapons).

As for Israel, it is impossible to ignore how much, in American politics, the Iran issue is an Israel issue. The Netanyahu government’s own repeated invocation of an Iranian nuclear threat has several roots, including the desire to preserve Israel’s regional nuclear weapons monopoly, the usefulness of having Iran stand in as the region’s “real problem” to divert attention from the festering Israeli-Palestinian conflict, and simple emotion and fear. What American politicians don’t seem to understand but any reader of Haaretz would know is that many leading Israelis, whose experience demonstrates both their deep commitment to Israel’s security and their expertise in pronouncing on it, see the issue differently. Former Mossad chief Meir Dagan described the idea of an Israeli air strike on Iranian nuclear facilities as “the stupidest thing I have ever heard.” Another former Mossad head, Efraim Halevy, and the current director of the service, Tamir Pardo, have both recently denied that an Iranian nuclear weapon would be an existential threat to Israel. Even Defense Minister Barak, in an interview answer from which he later tried to backtrack, acknowledged that any Iranian interest in a nuclear weapon was “not just about Israel,” but an understandable interest given the other countries that are already in the nuclear club.

If Iran acquired the bomb, Israel would retain overwhelming military superiority, with its own nuclear weapons—which international think tanks estimate to number at least 100 and possibly 200—conventional forces, and delivery systems that would continue to outclass by far anything Iran will have. That is part of the reason why an Iranian nuclear weapon would not be an existential threat to Israel and would not give Iran a license to become more of a regional troublemaker. But a war with Iran, begun by either Israel or the United States, would push Israel farther into the hole of perpetual conflict and regional isolation. Self-declared American friends of Israel are doing it no favor by talking up such a war.