Though Iran describes its drone and missile attack on Israel as “retaliation,” it is actually an act of aggression. If Iran were an already-nuclear enemy state, Israel’s capacity for lawful self-defense would be glaringly limited. But as Iran is still pre-nuclear, the Iranian aggression could prove net-gainful for Israel. In essence, this Iranian crime offers Israel an 11th hour opportunity to prevent enemy nuclearization. In formal legal terms, such opportunity falls under the heading of “anticipatory self-defense.”

To be sure, the tangible human and material costs to Israel of any further escalation could be very high, but fighting against a not-yet-nuclear enemy that initiated the aggression would represent Israel’s best chance to avoid an eventual nuclear war.

Among other derelictions, Tehran’s earlier assurance that its strike against Israel would be limited “to avoid escalations” was disingenuous. After all, during any crisis search for “escalation dominance” by an already-nuclear Israel and a not-yet-nuclear Iran, competitive risk-taking would favor the former.

Under authoritative international law, defensive first strikes or acts of “preemption” could be permissible in existential-threat circumstances. But even if resorts to anticipatory self-defense would be deemed lawful or law-enforcing, they could still prove unreasonably dangerous, strategically misconceived, tangibly ineffectual, and/or irrational. It follows, going forward, that Israel will need to evaluate all anticipatory self-defense options along the two discrete standards of law and strategy.

From the standpoint of international law, preemption could represent a fully permissible option. Though subject to important constraints and conditions, the right of “anticipatory self-defense” is well established. And while a “bolt from the blue” Israeli preemption against Iran could involve assorted difficulties, such difficulties are unlikely to apply in an ongoing conventional war. In this connection, Iran had repeatedly declared its intention to strike Israel as “punishment.”

In law, this declaration, now fulfilled, was an open admission of mens rea or criminal intent.

The right of self-defense by forestalling an attack appears in Hugo Grotius’ Book II of The Law of War and Peace in 1625. Recognizing the need for “present danger” and threatening behavior that is “imminent in a point of time,” Grotius indicates that self defense is to be permitted not only after an attack has been suffered, but also in advance, that is, “where the deed may be anticipated.” Or, as he explains a bit further on in the same chapter, “It be lawful to kill him who is preparing to kill….”

A similar position was taken by Emmerich de Vattel. In Book II of The Law of Nations (1758), Vattel argues: “The safest plan is to prevent evil, where that is possible. A Nation has the right to resist the injury another seeks to inflict upon it, and to use force and every other just means of resistance against the aggressor. It may even anticipate the other’s design, being careful, however, not to act upon vague and doubtful suspicions, lest it should run the risk of becoming itself the aggressor.”

Grotius and Vattel draw upon the early Jewish interpreters, although the latter speak more generally of interpersonal relations than about international relations. Additionally, the Torah contains a prominent provision exonerating from guilt a potential victim of robbery with possible violence if, in self defense, he struck down and if necessary even killed the attacker before he committed any crime. (Ex. 22:1).

Even if Iran were not in a condition of active belligerency with the Jewish state, an Israeli preemptive action could still be law-enforcing. Israel, in the fashion of every state under world law, is entitled to existential self-defense. Today, in an age of uniquely destructive weaponry, international law does not require Israel or any other state to expose its citizens to atomic destruction. Especially in circumstances where active hostilities are already underway — that is, during times of conventional warfighting — Israel’s legal right to attack selected Iranian nuclear facilities would be unassailable.

Under current conflict circumstances, an Israeli non-nuclear preemption would represent the best available way to reduce the risks of a regional nuclear war. If Israel waits until the next “ordinary” war with Iran, that recalcitrant foe could conceivably launch nuclear attacks. Even if a then-nuclear Tehran would strike first with conventional weapons, Israel could still have no meaningful tactical choice but to undertake a nuclear retaliation.

The right of anticipatory self defense has its modern origins in the Caroline incident, an event that concerned the unsuccessful rebellion of 1837 in Upper Canada against British rule. Following this event, the serious threat of armed attack has generally been taken to justify a state’s militarily defensive action. In an exchange of diplomatic notes between the governments of the United States and Great Britain, then-US Secretary of State Daniel Webster outlined a framework for self defense which did not require an actual attack. In it, military response to a threat was judged permissible so long as the danger posed was “instant, overwhelming, leaving no choice of means and no moment for deliberation.”

These are bewildering matters. What should Israeli planners conclude? The answer depends in part upon their view of Iran’s reciprocal judgments concerning Israel’s leaders. Do these judgments suggest a leadership that believes it can gain the upper hand with a nuclear counter-retaliation? Or do they suggest a leadership that believes such counter-retaliation would bring upon Israel variously intolerable levels of adversarial destruction?

All relevant calculations assume rationality. In the absence of calculations that compare the costs and benefits of strategic alternatives, what will likely happen between Israel and Iran would remain a matter of conjecture. The prospect of non-rational judgments in this relationship is always plausible, especially as the influence of Islamist/Jihadist ideology remains strongly determinative among Iranian decision-making elites.

Iran’s attack on Israel is anything but a lawful retaliation.

Under all pertinent international law, Iran’s attack represents an overt act of aggression, but one that now also leaves Jerusalem with a not-to-be ignored opportunity to preemptively destroy selected Iranian military targets. Such a non-nuclear preemption opportunity could express the optimal way to prevent future and irremediably destructive nuclear aggressions from Iran.

While Israel’s active defenses have been remarkably successful against the Iranian missile and drone attacks, more offensive measures will be required. It could never be sufficiently purposeful or law enforcing for Israel to confine its reaction to the current Iranian attacks to passive strategies of interception. Above all other strategic considerations, the Iranian attacks, whether halted or ongoing, offer Israel a life-saving opportunity to avoid later preemptions against an already-nuclear enemy.

“The safety of the People,” observed ancient Roman philosopher Cicero, “is the highest law.” Now, the safety of the People of Israel could best be served by waging a just war against a pre-nuclear Iran. Though such a war might still involve significant human and material costs, it would be substantially less catastrophic than war between two already-nuclear powers. This is the case even if an Iran that had crossed the nuclear threshold was verifiably “less powerful” than a nuclear Israel. In any pertinent nuclear conflict scenario, even a “weaker” Iran could wreak intolerable harms upon Israel.

All things considered, if an ongoing or future war with Iran is inevitable, it would be much safer for Jerusalem to proceed as the sole nuclear combatant. Accordingly, this is not a moment for Israeli strategic thinking to become confused or shortsighted. Calculating that immediate war curtailment is necessarily the best available option would subject Israel to future instances of existential harm. This could include a full-scale nuclear war.

The author is Emeritus Professor of Political Science and International Law at Purdue University. Educated at Princeton (Ph.D., 1971), he is the author of twelve major books dealing with international relations, military strategy and world affairs. Dr. Beres was born in Zürich, Switzerland on August 31, 1945, and lectures and publishes widely on issues of terrorism, counter-terrorism, nuclear strategy and nuclear war. Professor Beres’ latest book is Surviving Amid Chaos: Israel’s Nuclear Strategy (2016; 2nd ed. 2018).  A version of this article was originally published by Israel National News.

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