In early October, U.S. officials accused Iranian operatives of planning to assassinate Saudi Arabia’s ambassador to the United States on American soil. Iran denied the charges, but the episode has already managed to increase tensions between Washington and Tehran. Although the Obama administration has not publicly threatened to retaliate with military force, the allegations have underscored the real and growing risk that the two sides could go to war sometime soon—particularly over Iran’s advancing nuclear program.

For several years now, starting long before this episode, American pundits and policymakers have been debating whether the United States should attack Iran and attempt to eliminate its nuclear facilities. Proponents of a strike have argued that the only thing worse than military action against Iran would be an Iran armed with nuclear weapons. Critics, meanwhile, have warned that such a raid would likely fail and, even if it succeeded, would spark a full-fledged war and a global economic crisis. They have urged the United States to rely on nonmilitary options, such as diplomacy, sanctions, and covert operations, to prevent Iran from acquiring a bomb. Fearing the costs of a bombing campaign, most critics maintain that if these other tactics fail to impede Tehran’s progress, the United States should simply learn to live with a nuclear Iran.

But skeptics of military action fail to appreciate the true danger that a nuclear-armed Iran would pose to U.S. interests in the Middle East and beyond. And their grim forecasts assume that the cure would be worse than the disease—that is, that the consequences of a U.S. assault on Iran would be as bad as or worse than those of Iran achieving its nuclear ambitions. But that is a faulty assumption. The truth is that a military strike intended to destroy Iran’s nuclear program, if managed carefully, could spare the region and the world a very real threat and dramatically improve the long-term national security of the United States.

DANGERS OF DETERRENCE

Years of international pressure have failed to halt Iran’s attempt to build a nuclear program. The Stuxnet computer worm, which attacked control systems in Iranian nuclear facilities, temporarily disrupted Tehran’s enrichment effort, but a report by the International Atomic Energy Agency this past May revealed that the targeted plants have fully recovered from the assault. And the latest IAEA findings on Iran, released in November, provided the most compelling evidence yet that the Islamic Republic has weathered sanctions and sabotage, allegedly testing nuclear triggering devices and redesigning its missiles to carry nuclear payloads. The Institute for Science and International Security, a nonprofit research institution, estimates that Iran could now produce its first nuclear weapon within six months of deciding to do so. Tehran’s plans to move sensitive nuclear operations into more secure facilities over the course of the coming year could reduce the window for effective military action even further. If Iran expels IAEA inspectors, begins enriching its stockpiles of uranium to weapons-grade levels of 90 percent, or installs advanced centrifuges at its uranium-enrichment facility in Qom, the United States must strike immediately or forfeit its last opportunity to prevent Iran from joining the nuclear club.

Some states in the region are doubting U.S. resolve to stop the program and are shifting their allegiances to Tehran. Others have begun to discuss launching their own nuclear initiatives to counter a possible Iranian bomb. For those nations and the United States itself, the threat will only continue to grow as Tehran moves closer to its goal. A nuclear-armed Iran would immediately limit U.S. freedom of action in the Middle East. With atomic power behind it, Iran could threaten any U.S. political or military initiative in the Middle East with nuclear war, forcing Washington to think twice before acting in the region. Iran’s regional rivals, such as Saudi Arabia, would likely decide to acquire their own nuclear arsenals, sparking an arms race. To constrain its geopolitical rivals, Iran could choose to spur proliferation by transferring nuclear technology to its allies—other countries and terrorist groups alike. Having the bomb would give Iran greater cover for conventional aggression and coercive diplomacy, and the battles between its terrorist proxies and Israel, for example, could escalate. And Iran and Israel lack nearly all the safeguards that helped the United States and the Soviet Union avoid a nuclear exchange during the Cold War—secure second-strike capabilities, clear lines of communication, long flight times for ballistic missiles from one country to the other, and experience managing nuclear arsenals. To be sure, a nuclear-armed Iran would not intentionally launch a suicidal nuclear war. But the volatile nuclear balance between Iran and Israel could easily spiral out of control as a crisis unfolds, resulting in a nuclear exchange between the two countries that could draw the United States in, as well.

These security threats would require Washington to contain Tehran. Yet deterrence would come at a heavy price. To keep the Iranian threat at bay, the United States would need to deploy naval and ground units and potentially nuclear weapons across the Middle East, keeping a large force in the area for decades to come. Alongside those troops, the United States would have to permanently deploy significant intelligence assets to monitor any attempts by Iran to transfer its nuclear technology. And it would also need to devote perhaps billions of dollars to improving its allies’ capability to defend themselves. This might include helping Israel construct submarine-launched ballistic missiles and hardened ballistic missile silos to ensure that it can maintain a secure second-strike capability. Most of all, to make containment credible, the United States would need to extend its nuclear umbrella to its partners in the region, pledging to defend them with military force should Iran launch an attack.

In other words, to contain a nuclear Iran, the United States would need to make a substantial investment of political and military capital to the Middle East in the midst of an economic crisis and at a time when it is attempting to shift its forces out of the region. Deterrence would come with enormous economic and geopolitical costs and would have to remain in place as long as Iran remained hostile to U.S. interests, which could mean decades or longer. Given the instability of the region, this effort might still fail, resulting in a war far more costly and destructive than the one that critics of a preemptive strike on Iran now hope to avoid.

A FEASIBLE TARGET

A nuclear Iran would impose a huge burden on the United States. But that does not necessarily mean that Washington should resort to military means. In deciding whether it should, the first question to answer is if an attack on Iran’s nuclear program could even work. Doubters point out that the United States might not know the location of Iran’s key facilities. Given Tehran’s previous attempts to hide the construction of such stations, most notably the uranium-enrichment facilities in Natanz and Qom, it is possible that the regime already possesses nuclear assets that a bombing campaign might miss, which would leave Iran’s program damaged but alive.

This scenario is possible, but not likely; indeed, such fears are probably overblown. U.S. intelligence agencies, the IAEA, and opposition groups within Iran have provided timely warning of Tehran’s nuclear activities in the past—exposing, for example, Iran’s secret construction at Natanz and Qom before those facilities ever became operational. Thus, although Tehran might again attempt to build clandestine facilities, Washington has a very good chance of catching it before they go online. And given the amount of time it takes to construct and activate a nuclear facility, the scarcity of Iran’s resources, and its failure to hide the facilities in Natanz and Qom successfully, it is unlikely that Tehran has any significant operational nuclear facilities still unknown to Western intelligence agencies.

Even if the United States managed to identify all of Iran’s nuclear plants, however, actually destroying them could prove enormously difficult. Critics of a U.S. assault argue that Iran’s nuclear facilities are dispersed across the country, buried deep underground and hardened against attack, and ringed with air defenses, making a raid complex and dangerous. In addition, they claim that Iran has purposefully placed its nuclear facilities near civilian populations, which would almost certainly come under fire in a U.S. raid, potentially leading to hundreds, if not thousands, of deaths.

These obstacles, however, would not prevent the United States from disabling or demolishing Iran’s known nuclear facilities. A preventive operation would need to target the uranium-conversion plant at Isfahan, the heavy-water reactor at Arak, and various centrifuge-manufacturing sites near Natanz and Tehran, all of which are located aboveground and are highly vulnerable to air strikes. It would also have to hit the Natanz facility, which, although it is buried under reinforced concrete and ringed by air defenses, would not survive an attack from the U.S. military’s new bunker-busting bomb, the 30,000-pound Massive Ordnance Penetrator, capable of penetrating up to 200 feet of reinforced concrete. The plant in Qom is built into the side of a mountain and thus represents a more challenging target. But the facility is not yet operational and still contains little nuclear equipment, so if the United States acted quickly, it would not need to destroy it.

Washington would also be able to limit civilian casualties in any campaign. Iran built its most critical nuclear plants, such as the one in Natanz, away from heavily populated areas. For those less important facilities that exist near civilian centers, such as the centrifuge-manufacturing sites, U.S. precision-guided missiles could pinpoint specific buildings while leaving their surroundings unscathed. The United States could reduce the collateral damage even further by striking at night or simply leaving those less important plants off its target list at little cost to the overall success of the mission. Although Iran would undoubtedly publicize any human suffering in the wake of a military action, the majority of the victims would be the military personnel, engineers, scientists, and technicians working at the facilities.

SETTING THE RIGHT REDLINES

The fact that the United States can likely set back or destroy Iran’s nuclear program does not necessarily mean that it should. Such an attack could have potentially devastating consequences—for international security, the global economy, and Iranian domestic politics—all of which need to be accounted for.

To begin with, critics note, U.S. military action could easily spark a full-blown war. Iran might retaliate against U.S. troops or allies, launching missiles at military installations or civilian populations in the Gulf or perhaps even Europe. It could activate its proxies abroad, stirring sectarian tensions in Iraq, disrupting the Arab Spring, and ordering terrorist attacks against Israel and the United States. This could draw Israel or other states into the fighting and compel the United States to escalate the conflict in response. Powerful allies of Iran, including China and Russia, may attempt to economically and diplomatically isolate the United States. In the midst of such spiraling violence, neither side may see a clear path out of the battle, resulting in a long-lasting, devastating war, whose impact may critically damage the United States’ standing in the Muslim world.

Those wary of a U.S. strike also point out that Iran could retaliate by attempting to close the Strait of Hormuz, the narrow access point to the Persian Gulf through which roughly 20 percent of the world’s oil supply travels. And even if Iran did not threaten the strait, speculators, fearing possible supply disruptions, would bid up the price of oil, possibly triggering a wider economic crisis at an already fragile moment.

None of these outcomes is predetermined, however; indeed, the United States could do much to mitigate them. Tehran would certainly feel like it needed to respond to a U.S. attack, in order to reestablish deterrence and save face domestically. But it would also likely seek to calibrate its actions to avoid starting a conflict that could lead to the destruction of its military or the regime itself. In all likelihood, the Iranian leadership would resort to its worst forms of retaliation, such as closing the Strait of Hormuz or launching missiles at southern Europe, only if it felt that its very existence was threatened. A targeted U.S. operation need not threaten Tehran in such a fundamental way.

To make sure it doesn’t and to reassure the Iranian regime, the United States could first make clear that it is interested only in destroying Iran’s nuclear program, not in overthrowing the government. It could then identify certain forms of retaliation to which it would respond with devastating military action, such as attempting to close the Strait of Hormuz, conducting massive and sustained attacks on Gulf states and U.S. troops or ships, or launching terrorist attacks in the United States itself. Washington would then need to clearly articulate these “redlines” to Tehran during and after the attack to ensure that the message was not lost in battle. And it would need to accept the fact that it would have to absorb Iranian responses that fell short of these redlines without escalating the conflict. This might include accepting token missile strikes against U.S. bases and ships in the region—several salvos over the course of a few days that soon taper off—or the harassment of commercial and U.S. naval vessels. To avoid the kind of casualties that could compel the White House to escalate the struggle, the United States would need to evacuate nonessential personnel from U.S. bases within range of Iranian missiles and ensure that its troops were safely in bunkers before Iran launched its response. Washington might also need to allow for stepped-up support to Iran’s proxies in Afghanistan and Iraq and missile and terrorist attacks against Israel. In doing so, it could induce Iran to follow the path of Iraq and Syria, both of which refrained from starting a war after Israel struck their nuclear reactors in 1981 and 2007, respectively.

Even if Tehran did cross Washington’s redlines, the United States could still manage the confrontation. At the outset of any such violation, it could target the Iranian weapons that it finds most threatening to prevent Tehran from deploying them. To de-escalate the situation quickly and prevent a wider regional war, the United States could also secure the agreement of its allies to avoid responding to an Iranian attack. This would keep other armies, particularly the Israel Defense Forces, out of the fray. Israel should prove willing to accept such an arrangement in exchange for a U.S. promise to eliminate the Iranian nuclear threat. Indeed, it struck a similar agreement with the United States during the Gulf War, when it refrained from responding to the launching of Scud missiles by Saddam Hussein.

Finally, the U.S. government could blunt the economic consequences of a strike. For example, it could offset any disruption of oil supplies by opening its Strategic Petroleum Reserve and quietly encouraging some Gulf states to increase their production in the run-up to the attack. Given that many oil-producing nations in the region, especially Saudi Arabia, have urged the United States to attack Iran, they would likely cooperate.

Washington could also reduce the political fallout of military action by building global support for it in advance. Many countries may still criticize the United States for using force, but some—the Arab states in particular—would privately thank Washington for eliminating the Iranian threat. By building such a consensus in the lead-up to an attack and taking the outlined steps to mitigate it once it began, the United States could avoid an international crisis and limit the scope of the conflict.

ANY TIME IS GOOD TIME

Critics have another objection: even if the United States managed to eliminate Iran’s nuclear facilities and mitigate the consequences, the effects might not last long. Sure enough, there is no guarantee that an assault would deter Iran from attempting to rebuild its plants; it may even harden Iran’s resolve to acquire nuclear technology as a means of retaliating or protecting itself in the future. The United States might not have the wherewithal or the political capital to launch another raid, forcing it to rely on the same ineffective tools that it now uses to restrain Iran’s nuclear drive. If that happens, U.S. action will have only delayed the inevitable.

Yet according to the IAEA, Iran already appears fully committed to developing a nuclear weapons program and needs no further motivation from the United States. And it will not be able to simply resume its progress after its entire nuclear infrastructure is reduced to rubble. Indeed, such a devastating offensive could well force Iran to quit the nuclear game altogether, as Iraq did after its nuclear program was destroyed in the Gulf War and as Syria did after the 2007 Israeli strike. And even if Iran did try to reconstitute its nuclear program, it would be forced to contend with continued international pressure, greater difficulty in securing necessary nuclear materials on the international market, and the lurking possibility of subsequent attacks. Military action could, therefore, delay Iran’s nuclear program by anywhere from a few years to a decade, and perhaps even indefinitely.

Skeptics might still counter that at best a strike would only buy time. But time is a valuable commodity. Countries often hope to delay worst-case scenarios as far into the future as possible in the hope that this might eliminate the threat altogether. Those countries whose nuclear facilities have been attacked—most recently Iraq and Syria—have proved unwilling or unable to restart their programs. Thus, what appears to be only a temporary setback to Iran could eventually become a game changer.

Yet another argument against military action against Iran is that it would embolden the hard-liners within Iran’s government, helping them rally the population around the regime and eliminate any remaining reformists. This critique ignores the fact that the hard-liners are already firmly in control. The ruling regime has become so extreme that it has sidelined even those leaders once considered to be right-wingers, such as former President Ali Akbar Hashemi Rafsanjani, for their perceived softness. And Rafsanjani or the former presidential candidate Mir Hossein Mousavi would likely continue the nuclear program if he assumed power. An attack might actually create more openings for dissidents in the long term (after temporarily uniting Iran behind Ayatollah Ali Khamenei), giving them grounds for criticizing a government that invited disaster. Even if a strike would strengthen Iran’s hard-liners, the United States must not prioritize the outcomes of Iran’s domestic political tussles over its vital national security interest in preventing Tehran from developing nuclear weapons.

STRIKE NOW OR SUFFER LATER

Attacking Iran is hardly an attractive prospect. But the United States can anticipate and reduce many of the feared consequences of such an attack. If it does so successfully, it can remove the incentive for other nations in the region to start their own atomic programs and, more broadly, strengthen global nonproliferation by demonstrating that it will use military force to prevent the spread of nuclear weapons. It can also head off a possible Israeli operation against Iran, which, given Israel’s limited capability to mitigate a potential battle and inflict lasting damage, would likely result in far more devastating consequences and carry a far lower probability of success than a U.S. attack. Finally, a carefully managed U.S. attack would prove less risky than the prospect of containing a nuclear-armed Islamic Republic—a costly, decades-long proposition that would likely still result in grave national security threats. Indeed, attempting to manage a nuclear-armed Iran is not only a terrible option but the worst.

With the wars in Afghanistan and Iraq winding down and the United States facing economic hardship at home, Americans have little appetite for further strife. Yet Iran’s rapid nuclear development will ultimately force the United States to choose between a conventional conflict and a possible nuclear war. Faced with that decision, the United States should conduct a surgical strike on Iran’s nuclear facilities, absorb an inevitable round of retaliation, and then seek to quickly de-escalate the crisis. Addressing the threat now will spare the United States from confronting a far more dangerous situation in the future.

Read more at Foreign Affairs' The Iran Debate: To Strike or Not to Strike.