Israeli Defense Minister Ehud Barak suggested recently that Israel's moment of decision on Iran would come not when it obtained nuclear weapons but, instead, how close Iran is to entering what he called "a zone of immunity." Barak's concern was that beyond this threshold it would no longer be possible to halt Iran's nuclear program.

What would comprise such a threshold? Increasingly, this means Iran's shifting of its enrichment activities to the underground facility in Qom as well as with the moving to Qom of more of the uranium previously enriched in Natanz. Barak seemed to imply that a military operation designed to abort Iran's nuclear efforts after the facility in Qom becomes fully operational would be meaningless or irrelevant -- it will be either impossible physically or so costly as to render it prohibitive.

Yet the focus on these issues illustrates the limits of public debate. Judging whether Israel can destroy Iran's nuclear installations from the air is difficult without access to classified information. It requires knowing, for instance, the operational capabilities of the Israeli Air Force to fly the distance carrying the required ordnance, to ascertain optimal (operationally and politically) flight paths that avoid a possible activation of other countries' air-defenses, and to bomb simultaneously multiple facilities scattered in various locations in Iran. None of the data relevant to addressing these issues is available in the public domain.

A specific example of this problem relates to the aforementioned concept of "a zone of immunity." Ascertaining the real meaning of this concept requires classified intelligence regarding the pace with which Iran is developing the facility in Qom, the rate and quantities of enriched uranium being moved from Natanz to Qom, the physical properties of the facility in Qom -- namely how well dug in the mountain it actually is and what other measures Iran has taken to protect it from air bombardment. It also requires relevant classified operational data about the capacity of the air forces of Israel and the United States to penetrate such fortified targets. Again, for obvious reasons, what exists in the public domain relevant to these questions is only an approximation of real data -- not accurate enough to reach a judgment about these critical issues.

Nevertheless, given the huge stakes involved, such questions must be debated if the United States and Israel are to avoid mindlessly stumbling into a costly military confrontation with Iran or an equally risky decision by default to avoid effective measures to arrest Iran's nuclear efforts. There are six important questions that fall under two big topics: the implications of Iran's possible acquisition of nuclear weapons and the ramifications of an attempt to prevent such acquisition by launching a military strike against Iran's nuclear installations.

The fundamental question is whether Iran's acquisition of nuclear weapons will actually amount to an "existential threat" to Israel. This might refer to the technical-physical capacity to destroy Israel, in much the same manner that the Soviets' possession of 26,000 nuclear warheads at the height of the Cold War implied the physical capacity to destroy the United States many times over. However, that would imply that once acquired, Iran would launch such weapons in efforts to end Israel's existence. Some suggest the actual threat is that such a hair-trigger environment would make Israel hostage to any small change in Iranian moods. As former Israeli Deputy Defense Minister Ephraim Sneh warned some years ago, that could breed such extreme Israeli anxieties as to induce its citizens to emigrate, also threatening Israel's existence. 

The central question is about deterrence. If efforts to arrest Iran's quest for nuclear weapons fails and Iran obtains them, will it be possible to deter it from using these weapons? Will Iran's leaders behave as rational actors so that deterrence -- which is based on leaders' ability to process and be sensitive to potential related costs -- could be applied effectively? Taking into account not only their rhetoric but more importantly their past behavior, what is the evidence suggesting that the "rational actor" assumption will not apply to Iran's leaders, therefore raising serious questions as to whether in this case a "deterrence fall-back" actually exists? Clearly, the policy implications of the first two questions are considerable because if a "deterrence fall-back" does not exist in the case of Iran, Israel will have no choice but to prevent it from obtaining nuclear weapons at all cost.

A second question is whether Iran's possible acquisition of nuclear weapons will lead to a nuclear cascade. For example, would Turkey, Saudi Arabia, and Egypt feel compelled to respond by developing nuclear capacities of their own, thus leading to a proliferation cascade? Having tolerated Israel's acquisition of nuclear weapons, would Egypt and Saudi Arabia be able to ignore a similar step by another non-Arab country in the region?

Another facet of this broader proliferation issue is what changes in Israel's nuclear posture Iran's acquisition of nuclear weapons would require. Would Israel continue to adhere to its present policy of nuclear ambiguity or will it sharpen its deterrent messages by adopting a more overt posture? And if so, would such a change further accelerate the proliferation of nuclear weapons in the region? Thus, if Iran's possession of nuclear weapons will lead Israel to feel that it must make its nuclear deterrence posture more overt, will this further press Egypt and Saudi Arabia -- and possibly Turkey -- to follow suit?

At the same time, should Iran's acquisition of nuclear weapons lead the United States to move quickly to prevent a proliferation cascade by offering its allies in the region a nuclear umbrella (otherwise referred to as "extended deterrence") how would these countries react? If Israel faces a choice between sharpening its deterrent message or accepting a U.S. nuclear guarantee, what are the pros and cons of the two possibilities? If Saudi Arabia and Egypt needs to choose between the costs and risks of attempting to develop an indigenous nuclear capacity or to accept a U.S. nuclear umbrella, is it self-evident that they would prefer the former over the latter? And how would their decision affect Israel's choice between accepting a U.S. nuclear guarantee and adopting a more overt nuclear deterrence posture?

In this scenario, how would Israel react if following Iran's acquisition of nuclear weapons other countries in the region follow suit to acquire their own, and Iran would announce that it is willing to implement nuclear arms control and disarmament measures as long as such measures are applied equitably "in a regional context?" Should Israel adopt the position that if disarmament measures could be credibly verified it would be better to have the two countries disarm their nuclear capabilities than to allow Iran to possess such weapons?

Third, what about the expectation that Iran's acquisition of nuclear weapons will embolden its allies in the region, encouraging them to behave more aggressively and to posit more dangerous challenges to Israel. This expectation requires thorough airing because it is not clear what Syria, Hezbollah, and Hamas would do that they are not doing already once Iran acquires nuclear weapons. If these parties take more bold actions because they assume that Iran's nuclear weapons will constrain Israel's responses to their more daring activities, the relevant scenarios should be simulated and explored. For example, is it realistic to expect that Iran's possession of nuclear weapons will affect the manner in which Israel will likely react to a Hezbollah cross-border attack and its abduction of an Israeli soldier?    

As noted earlier, a second set of issues that require exploration and debate concern the possible implications of an attempt to abort Iran's nuclear efforts with a military strike on its nuclear installations. The first of these concerns is the possibility that such a strike would lead Iran's allies and other Arab states to react strongly to the attack, possibly engulfing Israel in a regional war. The former head of Israel's Mossad, Meir Dagan, saw this scenario as quite likely but it is not clear on what evidence this is based. Syria is now overwhelmed by its domestic problems, if not civil war, and Hamas is increasingly disassociating itself from Iran's Syrian allies and is relocating its leadership in exile from Damascus to Cairo and Doha.

In this scenario, Hezbollah would be left alone to escalate, thus risking the likelihood that Israel would bring against it the full wrath of its military capacity, now restored in the aftermath of the summer 2006 debacle. Would Hezbollah risk its political survival to execute a Tehran-inspired retaliation? Similarly, it is not clear why other Arab states would play along with an Iran-inspired escalation and risk a confrontation with Israel when they did not react that way to Israel's 1981 bombing of Osiraq -- Iraq's nuclear reactor -- and to Israel's destruction of Syria's nuclear facility in 2007.

The second question associated with a possible Israeli military strike concerns its likely effects on Iran's domestic scene. Many observers expect such a strike to result in a "rallying around the flag" and a closing of the ranks behind its ruling regime. Thus, a military strike may stifle any prospects of "regime change" in Iran -- a change that some opponents of a military strike seem to regard not only as possible given the degree of discontent prevailing in Iran, especially among its large minorities, but also as the only long-term way of rendering Iran's nuclear efforts benign.

But is it self-evident that the Iranian public would necessarily "rally around the flag" in reaction to a military strike against the country's nuclear facilities? Could such a reaction be avoided by limiting the strike to facilities specifically associated with Iran's efforts to manufacture nuclear weapons -- thus minimizing civilian casualties -- by fully acknowledging Iran's right to a peaceful nuclear program, and by excluding from the bombing Iran's new energy-generating civilian nuclear power reactor in Busher?

A critical issue associated with a military strike is whether it would be wise for Israel to attack Iran's nuclear installations while the United States continues to oppose it arguing that such a step should be taken only after all other measures have been exhausted. The main question is not whether from a technical-operational standpoint Israel can conduct such a strike without U.S. permission given that it would require flying through or close to an area still defined as a "U.S. Theater of Operations." By early 2012 this issue has been somewhat reduced with the end of U.S. military presence in Iraq. More important is whether given Iran's threat to retaliate against an airstrike by targeting U.S. forces and assets in the region, Israel can ignore the costs that the U.S. may incur for such a strike. Indeed, even if Iran does not target U.S. forces in the region directly, any reaction by Iranian forces could ignite and pull the United States into a broader violent conflict in the Middle East. Would such unintended U.S. involvement in another war in the region invite U.S. anger directed at Israel?  

And even more broadly, given the growing intimacy of U.S.-Israeli defense cooperation, can Israel afford to ignore U.S. priorities and concerns? Addressing this issue on November 1, 2011 Defense Minister Ehud Barak reportedly told the Knesset Committee on Finance that there are times when a nation is required to defend itself even at the displeasure of its closest allies. But would it be responsible to do so in this case? Given that Israel will continue to face serious challenges in an ever-changing Middle East, and will continue to require U.S. assistance at almost every level, can Israel discount the U.S. will? Conversely, would Israel be able to diminish the expected negative U.S. reaction to its self-interested measures by meeting U.S. priorities in other fronts? For example, by doing its share to mend fences with Turkey -- a member of NATO and a close and important ally of the United States?

Much of the discussion of the prospects of Iran's acquisition of nuclear weapons, and of the efficacy of the efforts to prevent it from doing so, continues to focus on operational dimensions of this issue. Yet judgments regarding these dimensions cannot be rendered in the absence of relevant classified data. Instead, the public debate must focus on the strategic dimensions of the issue -- a realm in which civilian strategists have much to contribute. Indeed, airing these dimensions is an absolute imperative. Without it we are condemned to repeat the mistakes of the past or to commit worse ones. More important, without such airing we are doomed to step mindlessly closer and closer to a military confrontation with Iran or, possibly just as dangerous, to accept and accommodate its nuclear ambitions and designs.        

Brig. Gen. (ret.) Shlomo Brom is a former Head of Strategic Planning in the IDF's Planning Branch. He is a Senior Research Associate at the Institute for National Security Studies (INSS) in Tel Aviv; Prof. Shai Feldman is Director of the Crown Center for Middle East Studies at Brandeis University and a former Head of Tel Aviv University's Jaffee Center for Strategic Studies; Amb. Shimon Stein, a former Deputy Director General of Israel's Foreign Ministry and a former Israeli Ambassador to Berlin is a Senior Research Fellow at INSS.