When considering the dangers of an Iranian nuclear weapons program, those who differ on political ideology find rare common ground. According to nearly everyone, if Iran develops nuclear weapons, its neighbors will inevitably do so, too. Former U.S. Senator Sam Nunn (D-Ga.), for example, said earlier this year, "The governments of the world must understand what a threat it is if the Iranians get nuclear weapons, because there are probably 10 other countries in the Middle East over the next 10 to 20 years that would follow down that road." U.S. policymakers from John Bolton, the conservative former U.S. ambassador to the UN, to Vice President Joe Biden all seem to agree with this dark prediction.

But there's one problem with this "nuclear domino" scenario: the historical record does not support it. Since the dawn of the nuclear age, many have feared rapid and widespread nuclear proliferation; 65 years later, only nine countries have developed nuclear weapons. Nearly 20 years elapsed between the emergence of the first nuclear state, the United States, in 1945, and the fifth, China, in 1964.

The next 40 years gave birth to only five additional nuclear countries: India, Israel, South Africa, Pakistan, and North Korea. South Africa voluntarily disarmed in the 1990s, as did Belarus, Kazakhstan, and Ukraine following the dissolution of the Soviet Union. After Israel developed a nuclear weapons capability in the late 1960s, no regional nuclear chain reaction followed, even though the country is surrounded by rivals. Nor was there even a two-country nuclear arms race in the region.

Similarly, it has now been four years since North Korea became a nuclear weapons state, yet South Korea and Japan have not followed suit, despite the fact that they have a latent nuclear weapons capability -- access to the fissile material necessary for nuclear weapons. These countries' decisions to not go nuclear are largely thanks to extensive U.S. efforts to dissuade them. Both South Korea and Japan enjoy firm and long-standing security assurances from Washington, including protection under the U.S. strategic nuclear umbrella, obviating the need for their own deterrents. Following North Korea's 2006 nuclear test, U.S. President George W. Bush immediately assured South Korea and Japan that the United States was unequivocally committed to protecting them.

The fruit of these efforts to prevent rapid and widespread nuclear proliferation, then, is the very reason a nuclear domino effect remains a myth. In the Middle East, there are no signs that the nuclear dominos will fall anytime soon. Although many governments believe that Iran could be one to three years away from developing a nuclear bomb, all other Middle Eastern countries (besides Israel) are at least 10 to 15 years away from reaching such a capability.

This time frame gives Washington ample opportunity to establish or reaffirm security pacts with countries that might be tempted to develop their own nuclear weapons programs in reaction to a potential Iranian bomb. In fact, that work has already begun. In July 2009, U.S. Secretary of State Hillary Clinton spoke of the possibility of the United States extending a "defense umbrella" over the Gulf region and shoring up those countries' military capabilities if Iran goes nuclear.

More generally, the United States is trying to reinforce a culture of nonproliferation in the Middle East. In late 2009, Washington concluded an agreement with the United Arab Emirates to forego the enrichment and reprocessing of nuclear fuel -- crucial steps in the development of nuclear weapons. (In return, the United Arab Emirates will receive help developing a civilian nuclear-energy program.) Similar overtures are being made to both Saudi Arabia and Jordan, states that are pursuing civilian nuclear-power programs to diversify their energy supplies.

Another achievement came during the 2010 Nuclear Nonproliferation Treaty Review Conference, when the United States endorsed the convening of a regional meeting on establishing a nuclear-weapon-free zone in the Middle East. The summit is due to be held in 2012 and, although Israel's nuclear weapons complicate matters, could serve as another step toward cementing a nonproliferation culture in the region.

These are major accomplishments in preventing proliferation in the Middle East, and they contradict the worst-case scenarios about a nuclear Iran. Yet they have done little to reassure those who expect a chain reaction of proliferating states.

Such mistaken beliefs are due in part to the West's poor understanding of Iran. After more than 30 years of severed diplomatic, cultural, and educational relations with the country, the West knows little about Iran's leadership, national aspirations, and culture. Because of this, policymakers have a difficult time thinking about the implications of a nuclear Iran and resort to simplistic grandstanding, reprising outdated political fears that lack historical nuance or modern perspective. The exaggerated fears have been useful, too: had the United States not presented Iran's nuclear aspirations in the darkest of lights, it may not have been able to gain support for four rounds of UN sanctions against the Islamic Republic in the last few years.

Another reason for the persistence of worst-case thinking is that the domino analogy is often discussed interchangeably with bilateral arms races, such as those between the United States and the former Soviet Union, and between India and Pakistan. These are two distinct concepts, however. The Cold War and South Asian cases represent dyadic arms buildups -- a scenario that cannot be ruled out in the Middle East. Even though this hypothetical should be of great concern, it is far from the nightmare nuclear domino effect, which by definition requires many more countries to speedily develop nuclear weapons. In the Middle East, this type of rapid development is just not technologically feasible.

None of this means that the world need not worry about Iran's nuclear program. Slow-bleed proliferation still has profound implications for international peace and security. Most worrisome is the prospect of a terrorist organization gaining access to a nuclear weapon or materials for a dirty bomb -- a possibility more likely in a world with more nuclear states producing fissile materials. Human or technological error is another legitimate reason to worry; on several occasions during the Cold War, the world came close to nuclear war due to miscommunications between nuclear weapon states.

More broadly, the world does not need additional nuclear hot spots. Look no further than India and Pakistan, two archenemies that possess nuclear weapons and occasionally come to the brink of nuclear war. Adding a nuclear component to the animosity between Israel and Iran would not improve prospects for lasting peace in the region.

Other fears about a nuclear Iran are less convincing. It is often said, for example, that Iran's neighbors will be held hostage to Tehran's atomic tyranny. Undoubtedly, a nuclear Iran will gain regional prestige and power, and the country would be able to exert increased pressure on other nations. But the offensive utility of nuclear weapons is questionable; they have not been used since Hiroshima and Nagasaki. All other nuclear powers have relied on their nuclear capabilities for deterrence, and there is no reason to believe that Iran would act differently. Any Iranian threats to use nuclear weapons would simply not be credible. And without credibility, Iran -- like any country -- would not be able to hold another country hostage.

Others claim that the global nonproliferation regime would quickly crumble if Iran went nuclear. According to them, a nuclear Iran may damage the Nuclear Nonproliferation Treaty (NPT), the agreement under which states endorse nuclear disarmament and pledge not to develop nuclear weapons. If Iran were to emerge as a nuclear weapons state after cheating on its treaty obligations, the NPT's legitimacy would certainly suffer a blow. It would take more than Iran cheating on the treaty, however, to nudge the NPT into the abyss of irrelevance. The NPT is one of the most successful international accords in history, currently enjoying almost universal membership. Its more than 180 committed parties are unlikely to allow Iran's nuclear program to demolish an institution that is -- and has been for four decades -- the foundation of nonproliferation efforts. And if Iran has the power to make the NPT collapse, it is questionable whether the treaty is worth preserving in the first place.

Predictions of catastrophic consequences resulting from a nuclear Iran are not only wrong but counterproductive. The assertion that the widespread proliferation is unavoidable could become a self-fulfilling prophecy. The myth of a nuclear domino effect creates an excuse for other Middle Eastern countries -- expecting that their neighbors will be nuclear powers -- to acquire nuclear weapons themselves.

Nightmare scenarios are dangerous for yet another reason: the expected consequences of a nuclear Iran, real or imagined, will determine the policies pursued to prevent Tehran from developing the bomb. If the consequences are out of sync with reality, the methods applied will be disproportional to the threat. Seven years ago, the United States walked into Iraq based on worst-case-scenario predictions about its nuclear program that were far from beyond a reasonable doubt. Washington cannot afford to wage another war on false pretenses.

There is no question that the world would be better off if Iran did not obtain nuclear weapons, and the international community must use all appropriate measures to prevent Iran -- or any other country -- from doing so. But the case against a nuclear Iran is strong enough without a nuclear domino myth. By invoking worst-case scenarios, policymakers are only clouding nuanced thinking.

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