[The following, by Barry Rubin, is crossposted from The Rubin Report.]

An Israeli attack on Iranian nuclear installations for the purpose of trying to stop Iran from obtaining nuclear weapons at all would be a mistake. Instead, Israel should plan--and indeed is planning--for a multi-layer campaign of airstrikes, missile defenses, and other measures in the event of Iran ever posing a specific threat of attacking Israel.

Before going into the details of why I'm saying this, however, let me stress that this is not something likely to be a central issue in the near-term future. That is precisely why we should discuss it now.

Let me also emphasize that Israeli plans should be in place such that if there ever would be an imminent threat of an Iranian attack, it should be preempted. What should be avoided, however, is an Israeli attack based merely on the goal of stopping Iran from obtaining nuclear weapons at all. It is far better to risk setting of a major regional war only if there is a need to do so, as happened, for example, regarding the 1967 war, a preemptive attack required for self-defense.

Of course, Iran's having nuclear weapons is an overall danger for Israeli interests, wider regional stability, and U.S. interests. Such a situation would in theory open Israel daily to the possibility of an Iranian nuclear attack. Yet history shows that Israelis would adjust to this situation, if remote as it would likely be, without panic or paralysis. Given a calm analysis, however, and the alternatives, a preemptive attack on Iran possessing a few nuclear weapons and long-range missiles would make matters worse, not better.

Here's why:

1. Iran is unlikely to attack Israel with nuclear weapons but if Israel attacks Iranian nuclear facilities such an outcome becomes inevitable. A state of open war would exist and the Tehran regime would be seeking revenge. All other options--containment, deterrence, a longer-run overthrow of the regime by domestic forces, a U.S.-Iran war based on accident or misperception--would be closed.

Moreover, by waiting to see how the situation develops, Israel will still, in the event of an apparent war crisis or a serious belief that Iran is going to attack, can always preempt in the future. The problem with the idea of attacking to prevent Iran from getting nuclear weapons is that it is based on the opposite view--a questionable assumption that an Iranian attack is inevitable in the near future.

Let me again emphasize that if Israel ever concludes on the basis of intelligence and actions by Iran that there is a real or imminent threat, it should react militarily.

It would be a mistake to base a belief that Iran is not going to attack Israel completely on the idea that Tehran's restraint or interests would prohibit such an outcome. We know the statements of Iranian leaders, their goals, and their ideology. Perhaps even more important, we know about the existence of factions within the regime that are very risk-oriented and the existence of even more extreme elements in the Islamic Revolutionary Guard Corps (IRGC).

Yet also to be taken into account are three additional points: limited Iranian capabilities; other Iranian goals, as aggressive as they must be; plus Tehran's fear of retaliation from Israel and the United States. It is the combination of these four factors that are persuasive.

Limited capabilities: For a very long period of time, Iran will only be able to launch a very small number of missiles against Israel simultaneously. Therefore, Israel and the United States could more easily counter such a threat, including by attacks against the launchers. In addition, over time an Israeli missile defense system and a parallel system for stopping rocket attacks (that would come from Hamas and Hizballah in response to any Israeli attack on Iran) would improve dramatically.

Given the small number of missiles fired by Iran at the same time, plus the U.S. and Israeli anti-missile systems, Iran's leadership would know that it could not knock out Israeli airfields. Thus, any attack on Israel would trigger massive destruction of Iran. And of course some of the missiles could easily miss Israel entirely (or be knocked down) so they would explode in Lebanon, Jordan, and the West Bank. Add to this the fact of U.S. warning systems, anti-missile defenses, and retaliation and the deck is highly stacked against Tehran.

The point here is not that the Tehran regime would be deterred by purely humanitarian considerations nor proceed in a calm and deliberate matter. But the level of "craziness" would have to be distinctly higher to start a war under these conditions.

In addition, a specific threat of any systematic Iranian attack would also have a warning period allowing Israeli leaders to decide to make retaliation possible on a specific occasion. And knowing that Israel would have plenty of capability for a second strike that would inflict huge damage on Iran, even if the Iranian attack enjoyed some success, would also be a deterrent on Iran.

Moreover, Iran is unlikely to launch a nuclear attack on Israel (and certainly not an immediate attack on obtaining nuclear weapons) is because that would interfere with Tehran's overall strategy. That is to use the nuclear umbrella to carry out a long-term, low-risk aggressive policy of supporting surrogates to destabilize or take over other countries, along with enjoying the fruits of intimidation and the resulting appeasement from Europe and Arabic-speaking countries that a nuclear Iran is likely to enjoy.

Once Iran goes nuclear its prestige in the Muslim-majority world among the masses is likely to rise sky-high. The strength of revolutionary Islamist movements, especially those allied to Iran, is going to increase. Arabic-speaking states know that they cannot rely completely on U.S. guarantees particularly at a time when a U.S. government proclaims that country's weakness. On a whole range of issues, Iran is going to make big gains.

Having nuclear weapons and having the West and Arabic-speaking world both deterred and pushed toward appeasement by fear of Iran's nuclear weapons is an advantageous situation for Tehran, which could subvert other countries and expand spheres of influence without fear of retaliation. By firing the weapons, those advantages would be lost.

2. No matter how it is conducted or even how much initial success it has, an Israeli attack is not going to do away with Iran's possession of nuclear weapons. It does not make sense to follow a strategy you know in advance will not work: to attack Iran to stop it from obtaining nuclear weapons when that effort will, at best, merely postpone Tehran getting them. At that point, following an Israeli attac and an Iranian crash program to rebuild facilities and get weapons, a nuclear war is a virtual certainty.

It is vital to understand that an Israeli attack will increase the likelihood of Iran firing nuclear weapons on Iran, after a period of time.

As one expert aptly put it:

"You can bomb an enrichment facility, but you can't bomb an enrichment program. (Or not one as well-developed as Iran's.) It's not like a reactor, with billions of dollars' worth of hard-to-replace capital piled up in one spot over the course of several years. Instead, it's thousands of interchangeable pieces that can be brought together and operated more or less anywhere."

And so, Iran would be able to rebuild after any such attack and, even if it took a few years, would be far more aggressive against Israel than it has been in practice up to that point. There is widespread agreement on this point including within Israeli military and political circles.

In addition, too much could go wrong with an Israeli attack, which could fail in part or whole if bombs miss the target, too many planes were lost, etc. Again, even a best-case outcome would not end the problem. It would, in fact, guarantee a large-scale future confrontation. And a partly failed raid would result in such a nuclear war happening immediately.

3. While the direct costs after such an operation are sustainable for Israel, they are likely to be high. If Israel faced an imminent threat from Iran, it would be worthwhile to bear such costs. In other words, if an attack were necessary to stop a specific plan or high level of likelihood that Iran would attack Israel with nuclear weapons, any cost would be worthwhile. But just to stop Iran from having nuclear weapons and long-range missiles in general does not validate such high costs.

The potential regional and international outcomes from an Israeli attack would include:

--Rocket attacks by Hamas and Hizballah along with border fighting.

--Increased Iranian attempts to sponsor terrorist attacks against Israel throughout the world.

--Possible attempted retaliation by Iran using unconventional weapons.

--A potential wider war between Iran and the West which would create serious Western resentment against Israel.

--Western criticism of Israel and perhaps serious problems in U.S.-Israel relations, especially with the Obama Administration in power.

While many Arab regimes would be happy at a successful Israeli strike, this would not bring any material benefits for Israel. The same would be true for Western satisfaction that Israel "took care of the problem."

Indeed, while an unsuccessful Israeli raid would be harshly criticized and might lead to sanctions on Iran, a successful Israeli raid would produce the reaction that since the danger would now be gone Israel could afford to make major concessions to the Palestinians and Syria.

Again, if Israel really faced the specific threat of an Iranian nuclear attack, such costs would be worthwhile, even limited in comparison to the problem. Yet why should Israel pay a high cost for the mere possibility that at some future time Tehran would go to war with Israel using nuclear weapons?

It should be stressed, too, that any attack on Iranian nuclear facilities would also not resolve the threat--no matter how high or low one assessed it to be--of Iran giving nuclear materials to terrorists. While this is a serious problem (and one often underestimated in the West), a military attack on Iran would actually increase the likelihood of this happening, since Iran would have radioactive materials but not perhaps the capability of delivering them by missile plus a thirst for revenge. Letting terrorists deliver the nuclear devices is an ideal solution for Tehran and would be perceived there as both lower-risk and higher-priority than it would be otherwise.

4. Finally, there is a rather ironic geostrategic aspect of this issue. If we are discussing certainties rather than scenarios, Iran's main threat in practice is not to Israel but to Arabic-speaking states and to U.S. interests.

Israel can defend itself; the Arab regimes cannot. Arab states are going to be intimidated and subverted internally by Iran; Israel will not engage in appeasement or face any significant increase in direct subversion or a conventional threat on its borders.

On the contrary, fear and preoccupation with Iran's threat will force Arab states to devote more attention and resources on that front. (The one exception is that Iran's ally, Syria, is likely to be bolder in fomenting attacks on Israel from Hamas and Hizballah smug in the knowledge that Tehran will protect it and that the United States won't put pressure on it.)

Why, then, should Israel engage in a high-risk, costly venture to protect countries like Saudi Arabia or Iraq that will do nothing to reciprocate or to reduce their own hostility to Israel?

Rather, it is the job of the United States to provide a regional umbrella against an Iranian nuclear threat. America must set up a defensive shield for its Arab state clients, which will also necessarily include Israel, provide them with assurances, and threaten Iran. In practice, this also means that the United States will have to support Israel's missile defense efforts and provide help in obtaining other military equipment Israel will need.

If Washington fails to handle containment properly, there will be a long period of testing in which it will have an opportunity to see the extent of the threat from Iran and its allies, notably Syria. This will lead either to a better U.S. policy on the issue or to Israel being able to readjust its strategy toward Iran as required.

During that period, Israel will always have the option to act if it perceives a direct and immediate threat to itself. Thus, it will not in any way be dependent on U.S. protection although it will also benefit from whatever is provided by Washington to defend Arab states or the region in general from an Iranian attack. Equally, if Iran is perceived as more aggressive, international support for Israeli action would be far higher than at the beginning of the Iran nuclear era.

It is not impossible that at some point Iran itself will provoke a war with the United States due to its subversive and terrorist efforts in Arabic-speaking countries; its interference with U.S. operations and shipping in the Persian Gulf; direct attacks by its surrogates on U.S. forces in Iraq, Afghanistan, or elsewhere; or its brinkmanship with nuclear weapons.

Of course, it is more likely that this will not happen, but if Iran does behave in this manner the world will blame it--and many countries will coalesce against it--in any resulting war. Why should Israel take on Iran all by itself, not only lacking international support but actually receiving international condemnation for doing so?

It would be a mistake, and one Israeli decisionmakers aren't going to make, to assume that Iran will immediately use nuclear weapons against Israel or that Israel can easily make the problem go away with a series of air attacks. Whatever public posture Israel's government uses about a possible military option--and one can certainly argue it is in Israeli, U.S., Western, and Arab interests for Tehran to perceive a real Israeli threat--actually to carry out such an attack would be a mistake.