Louis René Beres is professor of political science and international law at Purdue University, and retired Air Force Gen. John T. Chain was commander-in-chief, U.S. Strategic Air Command from 1986 to 1991.
It is the summer of 2011, and even the International Atomic Energy Agency in Vienna now concedes the obvious. Iran is closing in rapidly on full membership in the "nuclear club." When, probably in the next two years, such membership can be conclusively confirmed, Israel's preemption option will, by definition, have been lost irretrievably.
At that moment, the Jewish State's remaining strategic options will be limited to a hopefully still-optimal fusion of nuclear deterrence and active defense. One may also suppose, under the very best circumstances, that this residual fusion will be complemented by certain presumptively suitable forms of diplomacy. These could include both bilateral and multilateral international agreements. [Read news stories about national security, terrorism, and the military.]
The core of Israel's active defense plan for Iran remains the phased Arrow antiballistic 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. Iron Dome, a discrete and critical system designed to deal with shorter-range dangers, is intended primarily for the interception of rocket attacks from Gaza and Lebanon. For now, threats from Gaza and Lebanon do not have any unconventional or WMD elements.
From Israel's strictly technical side, everything looks very good. Test results for the Arrow, as well as for Iron Dome, continue to be positive.
It seems, therefore, that the cost implications of Israel's nearly-lost preemption option may now appear less than existential.
If Arrow were genuinely efficient in its expected reliability of interception, even an irrational Iranian adversary armed with nuclear and/or biological weapons might, in fact, be dealt with effectively. Even if Israel's nuclear deterrent were somehow made irrelevant by Iran, or by any other enemy state willing to risk certain and massive "counter-value" Israeli reprisal, an utterly worst-case scenario, that aggressor's ensuing first-strike could, theoretically, still be blocked by Israel's ballistic missile defenses (BMD). [See a slide show of 6 vulnerable terrorist targets.]
But there is a problem with such calculations. It lies in untenable assumptions about any system of BMD. No system of ballistic missile defense, anywhere, can be meaningfully judged as "reliable" or "unreliable." Reliability of intercept is an inherently "soft" concept, and any missile defense system will have "leakage." Whether or not such leakage could fall within acceptable levels must ultimately depend, in large part, upon the particular kinds of warheads fitted upon an enemy's missiles.
In assessing its still-evolving plans for nuclear deterrence, Israeli planners will need to closely anticipate the expected leakage rate of the Arrow. A small number of Iranian missiles penetrating Arrow defenses might still be deemed "acceptable" if their warheads contained "only" conventional high explosive, or perhaps even chemical high explosive. But if the incoming warheads were in almost any measure nuclear and/or biological, even an extremely low rate of leakage would be "unacceptable."
A fully zero leakage rate would be necessary to adequately protect Israel against any launched nuclear and/or biological warheads. Significantly, however, such a zero leakage rate is unattainable.
It follows from all this that Israel must move immediately to strengthen and refine its nuclear deterrence posture. To be dissuaded from launching an attack, a rational adversary would always need to calculate, among other things, that Israel's second-strike forces were sufficiently invulnerable to any considered first-strike attacks. By having to face the Arrow, this adversary could then require an increasing number of missiles before expecting to execute an assuredly destructive first strike against Israel. Here, Arrow would improve Israel's essential security not by offering any added physical protection, but rather by enhancing deterrence.