Now, facing an effectively unobstructed nuclear threat from Iran, Israel will need to choose prudently from among available strategic options. The most starkly polar of these choices would be (1) a "last minute" preemption using only conventional forces, or (2) a protracted and presumptively stable posture of nuclear deterrence. Should it opt for the former, a legally defensive first-strike known in more formal jurisprudence as “anticipatory self-defense,” Jerusalem could possibly hold back any further Iranian nuclearization, but only at more-or-less substantial cumulative costs.
There is more. Such extraordinary costs might need to be borne by Israel on several different fronts. Most likely, these would include not only the plausible prospect of variably destructive Iranian reprisals (even though, at this stage, using “only” conventional ordnance), but also an ominous assortment of surrogate terrorist attacks by Hezbollah. Already, some of these corollary attacks could involve chemical, biological, or even nuclear "dirty bomb" components. Naturally, following an Israeli preemption, however indispensable such defensive action would be to its physical survival, Jerusalem could expect a veritable whirlwind of coordinated international condemnations and related sanctions.
Should Israel’s leaders decline any eleventh-hour preemption option, and select instead a plan for deterring a now-impending Islamist nuclear adversary, a number of corresponding decisions would be required. These decisions would concern, inter alia, an expanding role for ballistic missile defenses, and also continuance or discontinuance of the beleaguered country’s historic policy of deliberate nuclear ambiguity. These ambiguity-related issues are more generally referred to as the “bomb in the basement.”
For Israel, confronting a nearly-nuclear Iran, the question of keeping the bomb in the basement could rapidly assume a primary urgency. At that point, it will have become essential for Jerusalem to communicate unambiguously to Tehran that Israel’s nuclear forces are sufficiently secure from enemy first-strikes,and sufficiently capable of penetrating enemy active defenses. 
It would also become necessary to assure Iran that Israel’s own nuclear weapons were plainly usable, that is, not of such an injuriously high yield as to be unrealistic implements of deterrence. This is because the deterrent efficacy of any single state's nuclear forces could sometime vary inversely with perceived destructiveness. In other words, seemingly small nuclear forces could actually offer more credible threats of unacceptable retaliation, than would be expressed by large nuclear forces.
Israel, oddly perhaps, should be attentive to some ongoing transformations of nuclear strategy in Islamic Pakistan. Here, observable in its own adversarial and already-nuclear dyad vis-à-vis India, Islamabad is openly tilting toward far smaller or "tactical" nuclear weapons. Since Pakistan first announced a test of its 60-kilometer Nasr ballistic missile back in 2011, the country’s “advertised” emphasis upon TNW seems to have been designed to more effectively deter a conventional war. Evidently, by threatening to use relatively low-yield or “battlefield” nuclear weapons for retaliation, Pakistan hopes, among other things, to appear meaningfully less provocative to Delhi.
With such a stance, Islamabad likely calculates, the unraveling country is less apt to elicit any nuclear reprisals.
To be sure, on conceptual levels, Israel vs. Iran is not analogous to India vs. Pakistan. For Israel, any nuclear retaliatory threats, whether still “ambiguous,” or newly “disclosed,” would need, above all, to deter an Iranian nuclear attack. Still, just as Pakistan has apparently calculated the benefits of issuing theatre nuclear deterrence retaliatory threats (to curb unwanted escalations from conventional to nuclear conflict), so too might Israel reason that it could better prevent the onset of conventional war with Iran by employing threats of TNW.
In the formal language of military professionals, such graduated strategic threats are prominently linked to “escalation dominance.”
Sometimes, in rendering complex strategic judgments, meaning can be counter-intuitive. Regarding necessary Israeli preparations for enhanced security from a nuclear Iran, there is an obvious but still-overlooked irony. In certain predictable circumstances, that is, the credibility of Israeli deterrent threats could be undermined by perceptions of too-great destructiveness. This means that one especially compelling reason for moving away from deliberate ambiguity, and toward certain limited forms of nuclear disclosure, would be to communicate that Israel’s retaliatory nuclear weapons were not too large.
Concerning the country's nuclear forces and doctrine, Israel’s decision-makers will need to proceed more self-consciously and explicitly with another basic choice. This decision would concern making a basic distinction between "assured destruction strategies,” and "nuclear war fighting strategies.” In narrowly military parlance, assured destruction strategies are sometimes called "counter-value," or “mutual assured destruction” (MAD) strategies.
These are essentially alternate theories of deterrence, postures in which a state primarily targets its strategic weapons on a presumed enemy’s civilian populations, and/or on its supporting civilian infrastructures. Although seemingly in violation of humanitarian international law, or the law of armed conflict (because it would seem to disregard the unwavering obligation to protect noncombatants), it is reasonable to argue that such targeting doctrines could reduce the probability of any actual nuclear war or nuclear exchange.
Nuclear war-fighting strategies are sometimes called "counterforce" strategies. In these more aggressive orientations to deterrence, a state primarily targets its strategic weapons on a presumed enemy’s major weapon systems, and also on some of its supporting military infrastructures. For nuclear weapon states in general, and for Israel in particular, there are very serious survival implications for choosing either one core strategy, or the other.
It is also possible that a country could consciously opt for some sort of "mixed" (counter-value/counterforce) nuclear targeting doctrine. In any event, whichever deterrence strategy Israel might choose, all that really matters is what the pertinent enemy state (in this case, Iran) would perceive as real.
War is microcosm. In strategic matters, as in life generally, the most deeply meaningful reality is perceived reality.
In choosing between two basic strategic alternatives, Israel could opt for nuclear deterrence based upon assured destruction. Here, Israel would assume an enlarged risk of "losing" any nuclear war that might still arise. Counter-value-targeted nuclear weapons, by definition, would not destroy military targets.
If, on the other hand, Israel were to opt for nuclear deterrence based upon counterforce capabilities, its Iranian enemy could then feel especially threatened, an unstable condition that could ultimately heighten the prospect of an actual nuclear exchange.
Going forward, Israel's decision on counter-value versus counterforce doctrines should be based, in part, on its prior investigations of: (1) enemy state inclinations to strike first; and (2) enemy state inclinations to strike all-at-once, or in stages. Should Israeli strategic planners assume that a nuclear Iran is apt to strike first, and to strike in an unlimited fashion (that is, to fire all of its nuclear weapons right away), Israeli counterforce-targeted warheads - used in retaliation - would likely hit only empty launchers. In such circumstances, therefore, Israel's only rational application of counterforce doctrine could be to strike first itself.
If, for whatever reason, Israel were to reject all still-available preemption options, there would be no reason to opt for a counterforce strategy. Rather, from the standpoint of persuasive intra-war deterrence, a counter-value strategy could then prove much more appropriate.
Should Israeli planners assume that a nuclear Iran is apt to strike first, and to strike in a limited fashion, holding some significant measure of nuclear firepower in reserve for follow-on strikes, Israeli counterforce-targeted warheads could still display certain damage-limiting benefits. Here, counterforce operations could serve both an Israeli preemption, or, should Israel decide not to preempt, an Israeli retaliatory strike. Further, should any Israeli first-strike be intentionally limited, perhaps because it would then be coupled with assurances of no further destruction in exchange for a prompt end to hostilities, these operations could productively serve an Israeli counter-retaliatory strike. Conceivably, Israel's attempt at intra-war deterrence could fail, occasioning the need for follow-on strikes, in order to produce badly needed damage-limitation.
Israeli preparations for nuclear war-fighting should not be understood as a distinct alternative to preparations for nuclear deterrence. Instead, such preparations should become essential and integral components of Israeli nuclear deterrence. After all, a vital connection may emerge between likely prowess/success in war, and the quality of pre-war nuclear deterrence.
In his illuminating 1982 book, The Bar Kokhba Syndrome, Yehoshafat Harkabi, a former Chief of Military Intelligence in Israel, examined a calamitous Jewish-historical event in the second century (132-135 AD/C.E.). Harkabi had sought to understand how an ill-fated ancient uprising could have pushed the Jewish People to the outer margins of history, and, more importantly, what specific strategic lessons might now be learned from “Bar Kokhba.” He concluded that (a) “In policy-making, to take a risk and to make sacrifices occasionally is necessary, but there is a limit to the dangers worthy of risk, for national existence is never to be jeopardized;” and (b) “…in (specifically) nuclear circumstances, refrain from a provocation for which the adversary may have only one response, nuclear war.”
Understood in terms of Israel’s present and most pressing security concerns, Harkabi would have favored virtually any promising Israeli measures intended to prevent Iran from ever becoming nuclear. Failing that option, he would likely have urged implementation of maximally stable nuclear deterrence between the two adversary states. Expressing the smallest expected probabilities of any catastrophic failure, this optimal system of deterrence would have been designed to convince Tehran that any use of its nuclear weapons, even in retaliation, would be irrational.
Such well-reasoned Israeli emphases on rationality could still fall on deaf ears, especially if the decision-makers in Tehran become more deeply concerned with fulfilling presumed "end times" expectations of Shiite religious doctrine. Nonetheless, short of viewing a prompt and residual preemptive attack on Iran as its only appropriate remedy, Jerusalem has no remaining choice but to proceed according to standard military planning assumptions of enemy rationality.
 The combination of Israel's costs could actually exceed their "mere" additive sum. This is because of the prospectively synergistic nature of any such combination. See, for example, Louis René Beres, "Core Synergies in Israel's Strategic Planning: When the Adversarial Whole is Greater than the Sum of its Parts," Harvard National Security Journal, Harvard Law School, June 2, 2015.
 Meeting these requirements brings up the issue of Israeli sea-basing (submarines). See, for example: Louis René Beres and (Admiral/USN/ret.) Leon "Bud" Edney, "Israel's Nuclear Strategy: A Larger Role for Submarine Basing," The Jerusalem Post, August 17, 2014; and Professor Beres and Admiral Edney, "A Sea-Based Nuclear Deterrent for Israel," Washington Times, September 5, 2014. Admiral Edney was NATO Supreme Allied Commander, Atlantic.
First publihsed in Israel National News.