Iran is now probably within a year of becoming a nuclear weapons state. When that happens, Israel's preemption option will be gone. Ideally, however, the Jewish State's remaining strategic choices will then still include optimal and interrelated forms of nuclear deterrence and active defense.
The core of Israel's active defense plan for Iran remains the phased Arrow anti-ballistic missile program. Iron Dome is intended primarily for intercepting shorter-range rockets.
Looked at exclusively from Israel's technical side, everything looks very good. In principle, the implications of Israel's nearly-lost preemption option may remain tolerable.
But there is still a problem with premature optimism. It lies in untenable assumptions about any system of active defense. No system of ballistic missile defense can ever be altogether reliable.
Intercept system reliability is a "soft" concept: Any missile defense system will have "leakage."
A small number of Iranian missiles penetrating Arrow defenses might be "acceptable" if their warheads contained "only" conventional or chemical payloads. But if the incoming warheads were in any measure nuclear and/or biological, even an extremely low rate of leakage would be unacceptable.
Now, Israel must move, recognizably, to strengthen its still-ambiguous nuclear deterrence posture. To be dissuaded from launching an attack, a rational adversary would always need to calculate that Israel's second-strike forces could outlast any contemplated first-strike aggressions.
Facing the Arrow, this adversary could require steadily increasing numbers of missiles in order to achieve an assuredly destructive first-strike against Israel. But once Iran were able to assemble a certain determinably larger number of deliverable nuclear warheads, Arrow could cease to serve its deterrent function.
What if the Iranian leadership does not act according to rational behavior? What if Tehran does not value Iran's national survival as a state above all else?
Such circumstances, improbable, but still possible, could render it impossible to deter an Iranian nuclear adversary with any threats of "massive retaliation" and/or "flexible response."
Nonetheless, Israel must continue to develop, test and implement an Arrow-based interception capability to match the cumulative enemy threat. It must also take corollary steps to enhance the credibility of its opaque nuclear deterrent.
More precisely, Israel must prepare to take its bomb out of the basement on short notice, and to make operational a recognizable second-strike nuclear force. This force, hardened and dispersed, must be ready to inflict an unacceptable retaliatory salvo against identifiable enemy cities.
Israel must also clarify that Arrow defenses would always operate simultaneously, or in tandem, with Israeli nuclear retaliations. Iran must, therefore, be made to understand that Israel's Arrow deployment will never preclude, or even render less probable, an Israeli nuclear reprisal.
In the very best circumstances, Iran would never have been allowed to develop a nuclear program with impunity. Now, however, Israel will have to deal with a persistently recalcitrant enemy regime by implementing steady enhancements of both its nuclear deterrence and active defense capabilities.
Although regime-change in Tehran might first appear as an attractive alternative option, Israel should understand that any such transformation could, at best, offer only temporary national security benefits.
Soon, Iranian nuclear peril could be directed toward Israel not only via direct missile strike, but also by way of terrorist-proxy delivery systems, including cars, trucks and boats. Should a newly-nuclear Iran ever decide to share its weapons-usable materials and scientific personnel with Hezbollah in Lebanon, Israel might then have to face a heightened prospect of nuclear terrorism.
For Israel, even comprehensive efforts at upgrading nuclear deterrence postures and long-range active defenses could be insufficient. To deal satisfactorily with the less visible but still-urgent derivative component of an Iranian nuclear program, a deliberate strategy for inflicting nuclear terror, Israel will have to accelerate its layered integration of Iron Dome with Arrow.
In the absence of viable preemption options, such acceleration may also prove indispensable to secure protection from expressions of enemy irrationality in Tehran.
Louis Rene Beres is professor of political science and international law at Purdue. The author of many major books in the field, he was chairman of Project Daniel (Israel ).
U.S. Air Force Gen. John T. Chain (Ret. ) was commander-in-chief of the U.S. Strategic Air Command and director of the Joint Strategic Target Planning Staff. He has also served as chief of staff of the Supreme Headquarters Allied Powers Europe and director of the U.S. State Department's Bureau of Politico Military Affairs.
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