This PolicyWatch is the third in a three-part series. Part I, by Michael Eisenstadt, examined the political and military challenges of preventing an Iranian nuclear breakout; Part II, by Michael Knights, examined the operational challenges of preemptive action.
A U.S. or "coalition" strike against Iran's nuclear program would be an exercise in high-stakes compellence. Although the physical results of such a strike (e.g., amount of damage inflicted; number of years by which the Iranian nuclear program would be set back) are uncertain, the consequences for U.S.-Iranian relations are not. Whatever the core purposes of the Iranian nuclear program -- defensive-deterrent or offensive-coercive -- attacking a program of vital national importance is tantamount to initiating long-term hostilities with Iran. Washington must assume that Iran would seek to punish its attackers. Its reaction to a strike, especially over the mid- to long-term, would be calculated, creative, and challenging for the United States and any participating allies. Iran would be prepared to wait to deliver punishment, maximizing its chances and effects through careful planning and execution.
Nature of the Attack
To a degree, the Iranian reaction would likely be contingent on the nature of the attack on its nuclear program. It is quite possible, however, that the Iranians would react to even a limited strike as if it were a general attack on the program, perhaps even on the regime and state. Given the broad scope of the Iranian program, the United States would have to mount a comprehensive attack aimed at several key facilities in order to significantly stunt its progress. Any such operations would need to be precise and effective. Key facilities and components would need to be completely destroyed or rendered useless, and this level of damage is not always easy to achieve.
To the extent that the United States could obscure its role via a covert strike, the Iranian reaction might be less focused. Yet, there is little chance that responsibility for a comprehensive attack, even if conducted by covert means, could be avoided for long. Indeed, Iran might react against the United States even if the attack were carried out by a U.S. ally such as Israel.
A direct U.S. attack with cruise missiles and manned aircraft would have the best prospects for setting back Iran's nuclear program. Yet, such an attack could evolve into a large and complex campaign, requiring significant support operations to suppress Iranian air defenses; provide combat search-and-rescue services; eliminate Iran's ability to retaliate immediately with air, missile, or naval units; and conduct "re-strikes" if the initial attacks were less successful than intended.
Iran's reaction to U.S. strikes can be considered in three time frames: immediate, mid-term, and long-term. In the immediate period, including during the strikes themselves, Iran would undertake primarily defensive measures. It would mount the most robust defense it could with its air and air-defense forces. It would also attempt to attack any locatable launch points for the strikes. As the operation unfolded, Tehran would assess whether it represented a limited attack on the program or a comprehensive attack on the regime. Tehran would then place noninvolved forces on alert, disperse high-value assets (including leadership assets and missile forces), and implement contingency plans (including internal security plans) for a wider attack. It might also prepare to close the Straits of Hormuz, readying mines, small boats, and coastal defense missiles and reinforcing its presence on the Persian Gulf islands.
As the attack concluded, Iran would assess the damage done and assign responsibility. Significant losses to the civilian population from the release of radioactive material would be an especially dangerous situation, with Iran potentially reacting by employing chemical or biological weapons. Even if its immediate reaction were completely conventional, however, Iran could rapidly broaden its effect by involving other states in the region, striking at U.S. assets in reach, and threatening oil shipments through the straits. Hence, the United States would likely have to contend with a general Gulf crisis.
Mid-term Reaction. In the mid-term, and assuming the situation did not rapidly escalate to major hostilities, Tehran would adopt a more deliberate approach. Iranian decisionmakers would begin weighing options for a calculated and appropriate response. They would launch a political-diplomatic offensive in the hopes of characterizing Iran as the aggrieved party, Finlandizing or intimidating regional players, and establishing the basis for the resumption of its nuclear program. They would then take available defensive and punitive measures in the region consistent with their political strategy. More important, they would initiate planning for strategic, long-term retaliation.
Long-term Reaction. In the long-term, Iran would attempt to take steps that would insure itself against another attack on its nuclear program or a broader attack on the regime. Tehran would almost certainly rebuild the program, reflecting its status as a high-value national asset. Unless significant numbers of scientists and technicians were killed in the strikes, there is no reason why Tehran could not restart the program; as long as it possesses the necessary knowledge and skills, Iran will have the basis for such a program. Indeed, Iran would likely accelerate both its nuclear and long-range-missile efforts in order to achieve a measure of deterrence as quickly as possible. The regime would also increase security for the program by instituting or increasing hardening, dispersal, redundancy, and active defense measures.
In addition, Tehran would likely plan and then implement asymmetric attacks on high-value U.S. and allied targets. A number of such possibilities exist, including using Hizballah to attack Israel with long-range rockets from southern Lebanon; launching asymmetric attacks on allied forces or on the transitional government in Iraq; attacking U.S. allies in the Gulf; or sponsoring terrorist operations against U.S. interests abroad or on U.S. soil. By using proxy elements, Tehran probably has a better chance of successfully arguing for plausible denial (at least with some audiences) than Washington would for any attack on Iran. Finally, the regime would attempt to use the U.S. attack as a means of rallying domestic political support. Any political forces seeking accommodation with Washington would be put on the defensive, if not written off completely.
The implications of a U.S. or allied strike against Iran's nuclear program are considerable. The United States would have to be prepared for a long-term conflict with an Iran that would seek out and attack weak points. Washington must weigh the costs and benefits of facing a more overtly hostile Iran following a strike as opposed to a nuclear-armed Iran in the not-too-distant future. Washington will also have to weigh the short-term benefit of delaying Iran's nuclear program against the possible long-term consequence of undermining those forces in Iran that want to improve U.S.-Iranian relations.
In the wake of an attack on Iran, Washington would need to demonstrate "escalation dominance" -- that is, holding other high-value Iranian targets hostage while making clear that still-worse things could happen to Iran if it retaliated against important U.S. targets or interests. The United States must also be ready to defend any of its allies that are within Iran's reach.