Nuclear deterrence is a game that even sane, rational governments may have to play, but there can be no assurance that enemies will always be rational. This presents a grave security problem, because the entire logic of nuclear deterrence rests squarely on the assumption that each state will always value its continued survival more highly than anything else. It follows that even a nuclear-weapons state able to destroy an aggressor after suffering an enemy first-strike attack could still lose the game.
A nuclear Iran is pretty much a fait accompli. For Israel, soon to be deprived of any remaining cost effective preemption options, this means forging a strategy to coexist with a nuclear Iran. This essential strategy of nuclear deterrence will call for reduced ambiguity about its strategic forces; enhanced and partially disclosed nuclear targeting options; substantial and partially disclosed programs for active defenses; recognizable steps to ensure the survivability of its nuclear retaliatory forces; and, to bring all these elements together, a comprehensive strategic doctrine.
In addition, because of the logical possibility of enemy irrationality, Israel's military planners must continue to identify suitable ways of ensuring that even a nuclear "suicide state" can be deterred. Such a perilous threat is very small, but it is not negligible. And although the probability of having to face such an irrational enemy state is low, the probable harm of any single deterrence failure could be intolerably high.
Israel Needs to maintain and strengthen its plans for ballistic-missile defense (the Arrow system), and also for Iron Dome, designed to guard against shorter-range rocket attacks. Still, these systems, including Magic Wand, which is still in the development phase, will inevitably have "leakage." Their principal benefit, therefore, must ultimately lie in enhanced deterrence rather than in any added physical protection.
For example, a newly-nuclear Iran, if still rational, would require steadily increasing numbers of offensive missiles to achieve a sufficiently destructive first-strike capability. Significantly, however, there could come a time when Iran will be able to deploy far more than a small number of nuclear-tipped missiles. Should that happen, Arrow, Iron Dome and, potentially, Magic Wand could cease their critical contribution to Israeli nuclear deterrence.
What if the leaders of a newly-nuclear Iran do not meet the expectations of rational behavior? What if this leadership does not consistently value Iran's national survival more highly than any other preference? In such unprecedented circumstances, Israel's leaders would need to look closely at two eccentric and more-or-less untried deterrence strategies, possibly in tandem with one another. First, they would have to understand that even an irrational Iranian leadership could have distinct hierarchies of preferences. Their task would be to determine precisely what these preferences might be (most likely, they would have to do with certain religious goals), and how these preferences are apt to be ranked in Tehran.
Second, Israel's leaders would have to determine the likely deterrence benefit of their own perceived irrationality. An irrational Iranian enemy could be less likely to strike first if it felt Israel's decision-makers were also irrational. Years ago, Gen. Moshe Dayan, then the minister of defense, said: "Israel must be seen as a mad dog; too dangerous to bother." Here, Dayan revealed an intuitive awareness of the possible benefits of feigned irrationality.
There is an antecedent point. Before Israel's leaders can proceed with any usable plans for deterring an irrational nuclear adversary, they must first be convinced that this adversary is in fact irrational, and not merely pretending irrationality.
Because all specific Israeli deterrence policies must be premised on the presumed rationality or irrationality of nuclear enemies, ascertaining precise enemy preferences should become the very first phase of strategic planning. It goes without saying that Israel's usual military assets should be carefully augmented by collaboration with its wider intelligence community.
Finally, as a newly-nuclear Iran could decide to share some of its fissile material with assorted terrorist groups, Israel's leaders may also have to deal with irrational nuclear enemies at the sub-state level. This prospect is likely much greater than that of irrationality at the national level. At the same time, the harm suffered from nuclear terror would probably be less overwhelming.
Soon, facing the prospect of a nuclear Iran, Israel must select refined and workable options to deal with two separate but interpenetrating levels of danger.
Should Iranian leaders be judged to meet the usual tests of rationality, Israel will have to focus especially on taking its Bomb out of the "basement," and on developing a retaliatory force that is appropriately hardened and dispersed. This second-strike nuclear force, counter value, not counter-force targeted, should be recognizably ready to inflict assured destruction against enemy cities.
Where Israel's leaders determine that they may have to deter an irrational enemy leadership, they will also have to consider the possible strategic benefits of appearing to be a "mad dog." Together with any such consideration, both Jerusalem and Tel-Aviv civilian and military leaders will need to determine what exactly is valued most highly by the country's enemies, and then prepare to issue fully credible threats to these enemy preferences.
Whether Iran's leadership is rational or irrational, Israel will need to continue with its expanding programs for cyber-defense and cyber-war.
In the past, a nuclear Iran could still have been prevented. But today, in the likely absence of any remaining options for "anticipatory self-defense," Israel's best available choice will be to deter an already nuclear Iran. Should it succeed in this indispensable objective, the security benefits would accrue not only to Israel itself, but also to the United States.