Are you afraid of Iran yet? Shrill warnings of war or imminent apocalypse over Iran's nuclear program have never been so strident, or so ominous.

A window is closing fast, the narrative goes, to prevent a fanatical and suicidal religious regime from acquiring the ultimate tools of Armageddon: nuclear weapons. Within months, some politicians claim, either Israel, the United States, or both may have no choice but to attack Iran to remove this "existential threat" to the Jewish state.

The world is facing another Hitler, declares Israeli Prime Minister Benjamin Netanyahu, and this moment of decision is akin to the eve of World War II. Iran is a threat to Israel and "a real danger to humanity as a whole," warns Israeli President Shimon Peres.

The tone on the US presidential campaign trail is no less dire. GOP hopeful Rick Santorum recently told a crowd that if Iran gets nuclear weapons, "let me assure you, you will not be safe, even here in Missouri." One of his opponents, former House Speaker Newt Gingrich, claims an Iranian strike on the US is "a real danger" that would make the 9/11 attacks look small. "Now imagine an attack where you add two zeros, and it's 300,000 dead," he said in early February. "This is not science fiction."

Yet it is also far from likely – even if Iran were to build a nuclear arsenal. In fact, say analysts and nonproliferation experts who have studied the effect of the bomb on countries, coexisting with a nuclear-armed Iran – or at least a nuclear-capable Iran – may well be possible, even inevitable, whether a military strike delays that outcome or not.

Analysts say Iran is not an irrational, suicidal actor that can't be deterred. Nor do they believe it is determined to destroy Israel at all costs. A recent Israeli think tank simulation of "the day after" an Iranian nuclear test came to the same conclusion: that nuclear annihilation will not automatically result.

Yet a nuclearized Iran would precipitate some profound changes across a chronically unstable region. Military balances would shift. Political relations among antagonists – and allies – would become more complicated. Israel would lose its nuclear hegemony in the Middle East.

Underlying it all loom major questions. Would Iran, implacable foe of the US and Israel, suddenly become beyond attack, like North Korea? Would Iran and Israel settle into a decades-long regional cold war, like that between India and Pakistan? Would Iran's jittery Persian Gulf neighbors rush to become nuclear powers themselves, setting off a dangerous and irreversible new arms race?

The questions swirled as Iran signaled on Feb. 16 that it was ready with "new initiatives" to resume long-stalled talks over its nuclear program with the US and other big powers. But the Iranians were nebulous about any possible concessions to previous Western demands – demands that diplomats say have only risen higher in a US election year. Renewed chances of talks came during a week when Tehran also proclaimed new advances in nuclear technology. As a result of all this, the possibility of any political breakthrough is far from certain.

It is not a fait accompli, of course, that Iran will build a bomb, even though it sometimes seems as if it is – and many Americans believe the country already has. As recently as 2010, for instance, a CNN poll found that 71 percent of Americans believed Iran has a nuclear arsenal.

Yet American intelligence agencies agree that Tehran hasn't yet decided to go for a nuclear bomb – and that even if it chose to, it would take years to create one and the means to deliver it. Israeli intelligence is also reported to have reached the same conclusion.

In testimony before Congress in late January, the US director of national intelligence, James Clapper, said Iran is "keeping open the option" to develop nuclear weapons. But, he added, "we do not know" if it will. The United Nations' nuclear watchdog agency, the International Atomic Energy Agency (IAEA), in its latest report last November, detailed alleged weapons-related work for the first time, but said "systematic" work was halted in 2003.

Tehran has long claimed it wants only to make nuclear power peacefully, and in Iran, embracing "nuclear rights" enjoys wide, popular support because it blends national pride and scientific prowess. Publicly, Iranian rulers profess to reject atomic weapons, and at the highest levels they evoke Islamic religious reasons to oppose all weapons of mass destruction.

Yet analysts and diplomats note that Iran does have many reasons to develop at least a "breakout" capability – the ability to assemble a bomb quickly should it want to. Tehran has watched modern history unfold around it and no doubt has drawn its own conclusions. Acquiring nuclear weapons helped preserve regimes in North Korea and Pakistan, for instance. But in Iraq and Libya, two nonnuclear countries, Saddam Hussein and Muammar Qaddafi were deposed. The Iranian media, in fact, tut-tutted last year that Mr. Qaddafi's fatal error was relinquishing his secret nuclear weapons program in 2004.

"If I was an Iranian national security planner, I would want nuclear weapons," Bruce Riedel, a 30-year veteran of the CIA now at the Brookings Institution in Washington, said in January.

"Look at the neighborhood that I live in: Everyone else has nuclear weapons who matters; and those who don't, don't matter, and get invaded by the United States of America," Mr. Riedel said on a panel hosted by the Atlantic Council, a Washington think tank.

In other words, the reason Tehran might pursue a bomb is the same one that has propelled every nuclear state in history: self-protection. Some analysts also believe that the main US tool to discourage Iran from developing weapons – stiff economic sanctions – might have the opposite effect.

"The danger is if you keep upping the sanctions [on Iran], there may be a point at which they have nothing else to lose," says Shahram Chubin, a Geneva-based Iran specialist with the Carnegie Endowment for International Peace. "If [they] see sanctions as regime threatening, then what is to stop [them] from going over [the top]?"

Yet few analysts see Tehran deciding to cross the nuclear threshold easily. In his testimony, Mr. Clapper said Iran's nuclear decisionmaking is guided by a "cost-benefit approach" – that its rulers would undoubtedly take into account the impact on the country's "security, prestige, and influence." Mr. Chubin says he expects Tehran to continue to quietly put all the elements in place – from stockpiling more enriched uranium that can be pushed to weapons-grade within a few months to improving its missiles – for a future "breakout," if the Islamic regime ever calculates that only weaponization will protect it from US or Israeli threats of attack.

What will likely not happen is that Iran will just one day flip a switch and build a weapon. Ambiguity has long been a part of the country's nuclear strategy. "I don't think there's going to be a day, and then a 'day after,' " says Chubin, author of "Iran's Nuclear Ambitions." "It's going to be blurry as it has been."

There is good reason for its opacity. Once it were to declare that it was a nuclear power, Iran would face all the international wrath and condemnation that would come with it – including for having violated the international Nuclear Non-Proliferation Treaty (NPT), to which it is a signatory.

"I think it's in their interest to go to the limit, bring their capabilities there, and then – when there are milestones – decide whether to go forward," says Olli Heinonen, the former head of safeguards at the IAEA, now at Harvard University's Belfer Center for Science and International Affairs. "Once you put it down that you have nuclear weapons, you are in a different situation. But while you have the ambiguity and people really don't know, and you have maybe not broken all the rules of the NPT, then you are much better off because you can then get some international support."

If Iran were to become a nuclear power, the most immediate question would be what it means for Israel, where warnings have reached histrionic heights.

"Absolutely nothing will happen," says Martin Van Creveld, an Israeli historian and author of some 20 books on military strategy. "Israel has what it takes to deter Iran, and the Iranians know it."

Mr. Van Creveld is implying that Israel's own nuclear arsenal of an estimated 200 warheads would prevent any Iranian first strike. Israel has the only such arsenal in the Middle East, and – unlike Iran's program – it has never been subject to UN inspection or safeguards.

"Say they build one bomb – it's not good enough. They need how many – 2, 3, 5, 10, 20? And that will take them a long time, so it's all nonsense," says Van Creveld. Iran is "not going to commit suicide by dropping the bomb – or even threatening to drop the bomb – on us."

A nuclear Iran would be destabilizing, but it would not threaten the existence of the US or Israel, he says – a view echoed by a number of senior Israeli security officials. Former Mossad chief Meir Dagan called an Israeli strike against Iran "the stupidest thing I've ever heard."

Riedel, of the Brookings Institution, envisions a kind of "mutual assured destruction" stability, too. Since the 1979 Islamic revolution, "there is no evidence to suggest the Islamic Republic of Iran is suicidal or seeking to end itself in a mass moment of Armageddon," he says. "In fact, to the contrary, the underlying motif of this revolution from Day 1 has been the survival of the revolution, to keep a revolution alive in Iran."

In Israel, even talking about living with a nuclear-armed Iran has long been taboo because it might appear to concede that what the US, Israel, and Europe have declared "unacceptable" is, in fact, acceptable. Yet that was the scenario of a simulation last October by the Institute for National Security Studies (INSS), an Israeli think tank affiliated with Tel Aviv University, that gave insights into what might happen across the region if Iran became a nuclear state.

The surprising result, the day after a hypothetical Iranian nuclear test, was not war. Instead, all the main players – from Washington to Moscow to Tel Aviv – adjusted rather easily to the new reality, with few dramatic changes in behavior.

Even Iran, rather than wielding its handful of new atomic bombs as a sword of Damocles over a fearful region, attempted "to use them to reach an agreement with the major powers to improve its strategic standing," according to the INSS report on the simulation published in January.

"The sky won't fall the day after," says Yoel Guzansky, a research fellow at INSS who shaped the simulation and was an Iran specialist in the Israeli prime minister's office for four years until 2009.

Other surprises to come out of the simulation included the Israeli team still threatening to use the military option against Iran even after the bomb test – Israel "stressed consistently that it cannot accept a nuclear Iran" – as well as a calming message from the prime minister's office that Israel was "well protected by advanced systems and will know how to respond if necessary." Overall, though, the response "was that a wide scale military attack against Iran is not in order," noted INSS.

For its part, the US opted for deterrence and containment of Iran in the short term, and applied "massive pressure" on Israel not to take military action that it implied would harm US-Israeli relations. In the long term, however, "the US goal was regime change in Iran, on the assumption that a different regime would be easier to contain."

The players in the simulation also examined the establishment of a regional security alliance of Sunni-dominated countries, notably Egypt and Saudi Arabia, to counterbalance the newfound power of Shiite Iran. Egypt pleaded with the US to advance a military option. Saudi Arabia suggested that it had already found its own way to counter Iran. It urged Pakistan to immediately honor the "nuclear commitments" formalized between the two countries over the years.

Interestingly, Russia proposed a Russo-American defense alliance aimed at ensuring the security of all states in the region. The initiative caught the rest of the countries by surprise. The new regional order would have enabled Israel and Iran to keep their nuclear weapons, bound others not to pursue them, and protected all members from internal meddling. The Russian aim was to prevent Iran from using its new nuclear capability to achieve regional political and military goals, including through attacks by its proxies, such as Hezbollah. The US opposed the deal, though, while other actors figured it would at least "neutralize Iran's nuclear blackmail power," the report said. Iran viewed the Russian move as recognition of its new status.

"I don't think the Iranians are going to throw a bomb at Israel the next day," says Mr. Guzansky. "Nuclear weapons are not for use; [they are] a powerful political tool.... It was interesting that Iran actually pressured to go back to the [negotiating] table and use this new capability to extract more.... This is another card for Iran."

The trigger in the simulation exercise was Iran conducting a nuclear test, in order to induce reactions among the players. But a more likely scenario is that Tehran slides into nuclear threshold status without fanfare.

"I think it's in their interest not to screw the last screw, not to [weaponize]," says Guzansky, "because no one will know where the Iranians are. And some actors may want to attack, [and] you have to be on your toes all the time.... Potentially it's even more destabilizing [than a test]."

In some ways, Iran is already there. President Mahmoud Ahmadinejad triumphantly announced in April 2006 that Iran had enriched its first grams of uranium. Dancers in traditional costume held glass and metal vials as the president proclaimed that Iran had "joined the nuclear countries of the world."

Iran has heralded its nuclear progress every step of the way, just as it has other scientific achievements, from its nanotechnology expertise to launching three satellites into space – a feat that puts it in a club of just nine other nations. Last December, Iran even brought down a CIA stealth drone that was spying on its nuclear facilities, claiming to catch it in an "electronic ambush."

"It is clear to Iranian strategists that nuclear weapons will not improve Iran's national security situation.... They do, however, see a value in technological progress," Bijan Khajehpour, an Iranian analyst at Atieh International, an Austrian-based strategic consulting firm, recently told the Muftah website.

Few Iranians forget these words of the prophet Muhammad, if only because they are printed with an atomic symbol on the 50,000 rial currency note: "If knowledge is to be found in the heavens, the Persians will go and get it."

A little girl appears on the TV screen, strolling through a pleasant field. She plucks the petals of a flower, innocently counting each one, until a somber voice takes over and begins counting down – "10, 9, 8 ..." It ends in an atomic explosion. Then a voice intones: "These are the stakes: to make a world in which all God's children can live, or go into the dark. We must love each other or we must die."

The TV spot, one of the most famous in American political history, is from the 1964 presidential campaign. It is a reminder that the issue of nuclear weaponry has long been a sensitive and sensational one, often punctuated with dire predictions of what might happen depending on whose hand is on the nuclear button in this country and who has an arsenal overseas.

In this case, the TV commercial wasn't warning explicitly about a rogue country getting the bomb. It was an ad by Democrats that was intended to imply that President Lyndon Johnson's opponent in the campaign, Republican Barry Goldwater, was trigger-happy and would, if elected, take actions that would engulf the US in a mushroom cloud. Goldwater had talked about giving NATO field commanders greater discretion in using tactical nuclear weapons and about the possibility of using atomic bombs in Vietnam. The Johnson team used these and other statements to depict Goldwater as an unstable warmonger.

Yet one reason the campaign was so effective was that the country was already anxious about the inexorable rise of the Soviet Union, under Nikita Khrushchev, as a nuclear power and even more notably over the emergence of a newcomer to the atomic club – "Red China." China tested its first atom bomb in October 1964.

"China in the 1960s was viewed, at least in the US, as a crazy state – certainly no saner, no more stable, no more understanding of the world than Iran is today, so in a sense we've been through this," says Robert Jervis, a professor of international politics at Columbia University in New York who has written extensively about nuclear deterrence.

Indeed, the Johnson administration in 1964 considered airstrikes to stop China's program, not unlike how President Obama today is weighing action against Iran. But the Texas Democrat eventually ruled it out, in part because he didn't want to provoke a confrontation in an election year.

"Mao [Zedong] made a series of highly irresponsible statements about the PRC [People's Republic of China] surviving and even thriving in a nuclear war," notes Francis Gavin, an international affairs professor at the University of Texas at Austin, in a 2009 paper in the journal International Security. "No country in the post-World War II period – not Iraq, Iran, or even North Korea – has given US policymakers more reason to fear its nuclearization than China."

Yet the day China's test happened half a century ago, Washington's description of the "threat" changed dramatically. Johnson told Americans that the military significance of China's test "should not be overestimated" because "many years and great efforts separate the testing of a nuclear device from having a stockpile of reliable weapons with effective delivery systems."

China's test did "not serve the cause of peace," Johnson added, "but there is no reason to fear it will lead to immediate dangers of war."

Within five years, in fact, the US and China began a covert dialogue and later started an anti-Soviet alliance that helped end the cold war.

"Nuclear weapons did not make China more hostile. If anything, its foreign policies became less aggressive and more mature over time," noted Dr. Gavin. "Nuclear weapons could make Iran more aggressive. Or, as with China, they could provide international legitimacy and security, making Iran less aggressive than it has been."

Columbia's Dr. Jervis agrees, and asks what the West has successfully deterred Iran from doing even without nuclear weapons. Lebanon's Iran-backed Hezbollah Shiite militia didn't hesitate to launch 4,000 rockets into northern Israel during the 2006 war, for instance. In the Persian Gulf in 2007, Iran seized 15 British Royal Navy sailors and held them for 13 days. Jervis says nuclear weapons are better used to "defend than to extend influence."

Still, other experts believe that an Iranian bomb could spark a regional arms race – or make Iran more bold in exerting its authority. In January, an analysis of the implications of a nuclear Iran published by the NATO Defense College in Rome warned of a "regional chain reaction" that "could endanger the Middle East's strategic stability."

Nuclear war or a "full-scale confrontation under the nuclear threshold are probably not driving Iranian strategic thinking," the NATO report said.

But new capabilities "could well prove to be an effective security umbrella for offensive non-nuclear activities" – as some argue they proved to be for Pakistan in stepping up violence against India after both sides tested nuclear devices in 1998.

The Pakistan-India example is, in fact, far less reassuring than that of China. The ability of nuclear weapons "to shield Pakistan against all-out Indian retaliation, and to attract international attention" actually encouraged aggressive Pakistani behavior, S. Paul Kapur of the US Naval Postgraduate School in Monterey, Calif., wrote in International Security in 2008. This, in turn, provoked forceful Indian responses – including a more aggressive conventional military posture. The tension did not lead to a nuclear or large-scale war, but "such fortunate outcomes were not guaranteed and did not result primarily from nuclear deterrence," he wrote.

This "stability-instability paradox" is one of the dangers experts worry about in the Middle East with a nuclear-armed Iran. The NATO analysis notes that while the region might be strategically stable because a conventional war is unlikely to escalate to a nuclear level, the very knowledge that there is a cap on how far conventional hostilities could go might unleash more military adventurism and foster instability.

The NATO report cites a Strait of Hormuz incident in January 2008, when a number of small, armed Iranian Revolutionary Guard boats closed in on three US Navy ships, coming within seconds of a firefight. The report asserted that a "much worse end result" may have been averted because a nuclear-armed Iran would have felt it could push further the limits of conventional war.

Other analysts doubt whether a nuclear Iran could successfully leverage its new power. A late January analysis by INSS argues that, other than preventing Israel from completely destroying Iran, the usefulness of a nuclear capability in advancing regular military and diplomatic goals is "not great." The INSS notes, for example, that Israeli forces would not refrain from responding against Hezbollah or Hamas if an Israeli soldier were kidnapped. Still, a nuclear Iran would "symbolize the end of an era in which the reigning image of Israel was as having a monopoly on deterrent capabilities."

NATO says it is "unlikely" that Iran would pledge nuclear protection of its proxies like Hezbollah – and makes no mention of sharing such hard-won nuclear technology with them, which is a frequent refrain of hawks and doomsday politicians.

Chubin states in his book on Iran's nuclear ambitions that "there is no reason to believe that Iran today, any more than Saddam Hussein earlier, would transfer WMD [weapons of mass destruction] technology to terrorist groups like Al Qaeda or Hezbollah."

Likewise, proliferation expert Joseph Cirincione, in his 2007 book "Bomb Scare," points out that nations like Iran and North Korea are "not the most likely sources for terrorists since their stockpiles, if any, are small and exceedingly precious, and hence well guarded."

Still, Tehran would revel in some NATO conclusions, especially regarding Iran's proxies: "Israel would have to operate in an uncertain environment, in which the fault lines for escalation would be unknown, and as a result escalation control could be extremely difficult."

The report also predicts that an Iranian bomb "would undoubtedly be a game changer for NATO partnerships," while adding the caveat that "since the dawn of the nuclear age, scenarios of rapid bursts of proliferation ... have abounded but never materialized."

elsewhere across the Persian gulf, an openly nuclear Iran would force reactions from many other countries – most notably among the Sunni sheikhdoms that have long feared Shiite Iran. Saudi Arabian officials have told American diplomats that they might seek nuclear weapons, and King Abdullah has repeatedly encouraged the US to attack Iran – to "cut off the head of the snake," in the words of one ambassador, according to US diplomatic cables published by WikiLeaks.

Despite these impulses, says Mr. Heinonen, Persian Gulf states would be more likely to follow the model of his native Finland, which in the 1960s served as a businesslike bridge between the Soviet Union and the West.

"From my perspective ... that's what going to happen with Kuwait, Bahrain, [the United Arab] Emirates," says Heinonen. "They will say, 'OK, let's not pick a fight here. After all, we all want to sell oil. There is a Big Brother that's behaving a little bit badly, but let's keep him happy and not antagonize him.' So I don't think a nuclear domino comes here."

Saudi Arabia and Egypt "might think differently," says Heinonen. Either way, the NPT is not likely to collapse.

Such analysis hasn't clouded the dark scenarios of many politicians and pundits, however.

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"Over the years [the Americans] developed a whole theology of fear about other countries acquiring nuclear weapons," says Van Creveld, the Israeli historian. "First was the Soviet Union, which we all know was hegemonic and expansionistic and Marxist and Godless, and they didn't like apple pie," he says. "Then it was against England and France, for all kinds of obscure reasons linked with NATO. Then it was Mao Zedong who was going to blow up the world, and then it was us [Israelis] though they never said so publicly. Then India ...

"All these thousands and thousands of [nuclear] warnings which have been issued since 1949, and none ... ever came true."