Why Israel Can’t Rely on Deterrence Against Iran’s Nuclear Program

Louis René Beres is professor of political science and international law at Purdue University.

For both Israel and the United States, the Iranian nuclear “clock” is now ticking faster. On August 21, beginning a process that will last about a month, uranium fuel shipped  by Russia began to be loaded into the Bushehr reactor. Once completed, this start-up of an Iranian nuclear plant will allegedly be monitored by the International Atomic Energy Agency.

What strategic options will remain available to Jerusalem and Washington? Soon, Israel will begin to deploy Iron Dome, a unique and promising system designed to deal with short-range rocket dangers. But what can now be done about the longer-range and much higher-consequence threats looming from Iran?

The core of Israel’s active defense plan for Iran remains the phased Arrow anti-ballistic missile program. Designed to intercept medium and short-range ballistic missiles, the various forms of Arrow  are expected to deal especially with Iran’s surface-to-surface missile threat.

From the technical side, everything is looking good. Test results for the Arrow, as for Iron Dome, continue to be strongly positive.

Yet, there are also some conceptual problems. Facing the prospect of a fully nuclear Iran, Israel must consider whether it can rely entirely upon a suitable combination of deterrence and active defense, or whether it must still prepare for preemption.

Can Israel “live” with a nuclear Iran? This is the critical question today. The answer will have life or death consequences for the Jewish State.

In principle, Israel’s preemption option may now appear less urgent. Many strategic planners and scientists believe that the Arrow’s repeated success in testing confirms that Israel is prepared to deal satisfactorily with any and all conceivable Iranian nuclear missile attack scenarios.

If Arrow were suitably efficient in its expected reliability of interception, even an irrational Iranian adversary armed with nuclear and/or biological weapons might be dealt with effectively. Even if Israel’s nuclear deterrent were somehow made irrelevant by Iran or another enemy state willing to risk certain and massive “counter-value” Israeli reprisal, that aggressor’s ensuing first-strike could still presumably be blocked by Arrow. Why, then, should Israel still consider preemption against Iran?

The answer lies in certain untenable assumptions about any system of ballistic missile defense. No system of ballistic missile defense, anywhere, can be correctly judged as simply “reliable” or “unreliable.”

Reliability of intercept is a “soft” concept, and any missile defense system will have “leakage.” Whether or not such leakage would fall within acceptable levels must ultimately depend largely upon the kinds of warheads fitted upon an enemy’s missiles.

In evaluating its disappearing preemption option vis-à-vis Iran, Israeli planners will need to consider the expected leakage rate of the Arrow. A tiny number of enemy missiles penetrating Arrow defenses might still be “acceptable” if their warheads contained “only” conventional high explosive, or even chemical high explosive. But if the incoming warheads were nuclear and/or biological, even an extremely low rate of leakage would plainly be intolerable.

A fully zero leakage-rate would be necessary to adequately protect Israel against any nuclear and/or biological warheads, and such a zero leakage-rate is unattainable.

Israel must move immediately to strengthen its nuclear deterrence posture. To be deterred, a rational adversary will need to calculate that Israel’s second-strike forces are invulnerable to any first-strike aggressions. Facing the Arrow, this adversary will now require increasing numbers of missiles to achieve an assuredly destructive first-strike against Israel.

With any non-rational adversary, however, all Israeli bets on successful deterrence would be off.

International law is not a suicide pact. Israel has the same residual right granted to all states to act preemptively when facing an existential assault. Known as anticipatory self-defense, this universal  right is affirmed in customary international law, and also in “the general principles of law recognized by civilized nations.” It is even supported by the 1996 Advisory Opinion on nuclear weapons issued by the International Court of Justice.