Louis Rene Berés is a professor of international law in the department of political science at Purdue University.
Before making his final preemption decisions on a still-nuclearizing Iran, Israel's Prime Minister Benjamin Netanyahu must first make a carefully informed judgment on Iranian rationality. In essence, he will have to determine, systematically and dispassionately, whether Iranian decision-makers are apt to be rational, irrational, or "mad." There are, in fact, critically significant differences between these three possible alternatives; the wisdom of any considered Israeli preemption will ultimately depend upon choosing correctly, and also on predicting Iranian policy behavior accurately over time.
Words matter. In world politics, irrational does not mean mad, or "crazy." It does mean valuing certain goals or objectives more highly than national survival. In such rare, but not unprecedented or inconceivable circumstances, a country's irrational leadership may still maintain a distinct and determinable rank-order of preferences. Unlike trying to influence a genuinely "mad" leadership, it is possible to effectively deter a ("merely") irrational adversary.
For the moment, and despite frequent popular caricatures in the world press, Iran is not a crazy or even radically whimsical state. Although it is true, at least doctrinally, that Iran's political and clerical leaders could sometime welcome the Shiite apocalypse more highly than avoiding catastrophic destruction, these decision-makers might nonetheless remain subject to alternative deterrent threats. If faced with such bewildering circumstances, wherein an already-nuclear Iran could not be prevented from striking first by the more usual and credible threats of retaliatory destruction, Israel would then need to identify, in advance, other less-orthodox, but still promising, threats of reprisal.
Inevitably, such alternative threats would concern those pre-eminent religious preferences and institutions deeply valued by Shiite Iran.
A presumptively rational leadership in Tehran would make it easier for Jerusalem to forego the pre-emption option. After all, in such vastly more predictable circumstances, Iran could still be deterred by some or all of the standard military threats linked to "assured destruction."
Unless there is an eleventh-hour defensive first strike by Israel, a considered attack that would most likely follow a determination of actual or prospective Iranian "madness"—a judgment that could either be correct or incorrect—a new nuclear adversary in the region will become a fait accompli. For Israel, this appearance would mandate a prudent plan to coexist or "live with" a nuclear Iran. Immediately, forging such an indispensable strategy of nuclear deterrence would call for reduced ambiguity about particular elements of its strategic forces; enhanced and partially disclosed nuclear targeting options; substantial and partially revealed programs for improved active defenses; certain recognizable steps to ensure the survivability of its nuclear retaliatory forces; further expansion of preparations for both cyber-defense and cyber-war; and, in order to bring all of these complex and intersecting enhancements together, in a coherent mission plan, a comprehensive strategic doctrine.
Additionally, because of the residual but still consequential prospect of Iranian irrationality (not madness), Israel's military planners will have to identify reliably suitable ways of ensuring that even a nuclear "suicide state" could still be deterred. Such a uniquely perilous threat might actually be very small, but, considered together with Iran's Shiite eschatology, it might not be negligible. Further, while the expected probability of having to face such an irrational enemy state could be very low, the disutility, or expected harm of any single deterrence failure, could still be unacceptably high.
Israel is steadily strengthening its plans for ballistic missile defense, both on the Arrow system, and on Iron Dome, a lower-altitude interceptor designed to guard against shorter-range rocket attacks, especially from Lebanon and Gaza. These systems, including others which are still in the development phase, will inevitably have leakage. It follows that because system penetration by even a single enemy missile carrying a nuclear warhead could, by definition, be intolerable, their principal benefit would ultimately not lie in supplying any added physical protection for Israeli populations. Instead, this still-considerable benefit would have to lie elsewhere, in expected enhancements of Israeli deterrence.