Operation Rising Lion and the Self-Defense Condition of Immediacy

On 13 June, Israel launched Operation Rising Lion, striking Iranian military leadership and critical infrastructure as well as key personnel involved in Iran’s nuclear weapons development program. Just over a week later, on 21 June, the United States conducted supporting attacks on Iran’s nuclear facilities at Fordow, Natanz, and Isfahan in Operation Midnight Hammer. Iran responded with strikes of its own (e.g., here and here).

The Israeli and American operations have collectively sparked a controversy across the international law community and condemnation by some States regarding their lawfulness under the jus ad bellum, the international legal rules governing the use of force by States. Debate surrounds whether Israel and the United States have valid claims to individual and collective self-defense, respectively. Some scholarly commentators have labeled the strikes manifestly unlawful (e.g., Milanovic; Gill; Haque). Others have reached the opposite conclusion with similar confidence (e.g., Tsagourias; Corn and Kittrie). Still others have been more equivocal and cautious in their characterizations (e.g., Schmitt; Cohen and Shany).

Despite disagreement, these commentators share some common ground. None contest, for example, that the strikes constituted a use of force that presumptively violated Article 2(4) of the UN Charter. Further, all agree that self-defense is the only available claim that could conceivably preclude the strikes’ wrongfulness. Nor is there any dispute that a notional nuclear ballistic missile attack by Iran would meet the prerequisite threshold of an “armed attack” under Article 51 of the Charter and customary international law triggering the right of a State to forcefully defend itself.

Instead, the gravamen of the argument is whether the Israeli and American operations complied with the customary conditions precedent to using force in self-defense: necessity (detailed further below); and proportionality. Discourse thus far has focused on necessity, with analyses coalescing on two general approaches. Some argue the condition, if required at all, was (and presumably still is) satisfied by virtue of an ongoing armed conflict between the two States (e.g., Corn and Kittrie; Cohen and Shany). Others have focused on whether the strikes were necessary to defend against prospective Iranian armed attacks, arriving at varying conclusions (e.g., Schmitt; Milanovic; Heller).

The strikes and their surrounding context raise the critical question of the life cycle of self-defense situations under international law. More specifically, considering they were but the latest in a chain of forceful exchanges with Iran, they beg which of necessity’s two temporal criteria, imminence or immediacy, should govern that condition’s analysis. In other words, throughout the course of episodic armed attacks, when does one end and another begin, such that it is appropriate to conduct a responding State’s jus ad bellum analysis anew?

The question may be of little practical significance as it pertains to isolated attacks or many conventional conflicts, such as that between Ukraine and Russia, where the use of force between States remains relatively intense and uninterrupted throughout their duration. But it is hardly academic in the context of conflicts, like that involving Israel and Iran, in which the recurring use of force is often punctuated and cyclical.

This post examines this intriguing question. Because the legality of the U.S. strikes depends on Israel’s individual self-defense claim, the post confines its analysis to Operation Rising Lion. Examination begins by outlining the temporal considerations that restrict the use of force in response to impending attacks. Next, it applies those frameworks to the Israeli strikes, including by assessing their broader context. To narrow its focus, the post does not address the companion condition of proportionality; nor does it address any issues under the law of armed conflict raised by the strikes (e.g., here and here).

Necessity, Imminence, and Immediacy

As mentioned, it is firmly settled that any use of force in lawful self-defense must be necessary to defend against an armed attack (e.g., Paramilitary Activities, para. 194; Nuclear Weapons, para. 41; Oil Platforms, paras. 43, 74, 76). A victim may therefore only use force as a last resort, that is, when “no practicable alternative means of redress” would suffice to address the threat (Dinstein, para. 656; Ruys, § 2.2.2.b.i). This being so, the criterion has long been interpreted to confine self-defense temporally. Despite some insistence that lawful self-defense is strictly limited to incipient or ongoing armed attacks (e.g., Dinstein, para. 586), there is growing consensus that anticipatory self-defense is permitted so long as an armed attack is imminent. As the term implies, a victim’s use of force may not occur too early, lest it constitute unlawful “preventive” self-defense. With respect to the strikes in question, it is this criterion that has monopolized much of the scholarly analyses to date.

Imminence is not the only criterion that regulates the timing of self-defense, however. Once an armed attack begins, the temporal lens shifts to one of immediacy. By it, a victim’s right to respond extinguishes once force is no longer necessary to repel an armed attack. In the usual case, there is little difficulty finding that force is necessary to terminate an ongoing attack. Assessment proves more difficult once an aggressor ceases the act(s) constituting its attack, for a victim’s response may not occur too late.

While several factors inform that analysis (see, e.g., Dinstein, paras. 755-57; Tallinn Manual 2.0, commentary to rule 73, para. 12), a controversial one is the prospect of future attacks. As set forth by the late Judge Ago, then-UN Special Rapporteur, in his 1980 Addendum to the Eighth Report on State Responsibility,

[A]rmed resistance to armed attack should take place immediately, i.e., while the attack is still going on, and not after it has ended. A State can no longer claim to be acting in self-defence if, for example, it drops bombs on a country which has made an armed raid into its territory after the raid has ended and the troops have withdrawn beyond the frontier. If, however, the attack in question consisted of a number of successive acts, the requirement of the immediacy of the self-defensive action would have to be looked at in the light of those acts as a whole. At all events, practice and doctrine seem to endorse this requirement fully, which is not surprising in view of its plainly logical link with the whole concept of self-defence (para. 122).

Under this approach to immediacy, the self-defense aperture widens, whereby intermittent attacks may be constructively treated as one collective use of force episode or phases in an integrated attack. Doing so is consistent with how international law approaches the resumption of hostilities following a ceasefire (as opposed to permanent terminations of armed conflict) with respect to the jus ad bellum (e.g., von Heinegg, p. 848-49; Schmitt, p. 379).

More importantly, it is endorsed by State practice and opinio juris, including previous U.S. exchanges with Iran. In written proceedings before the International Court of Justice in the Oil Platforms case, for instance, the United States asserted that the “use of force may be justified ‘when a State has good reason to expect a series of attacks from the same source and such retaliation serves a deterrent or protective function’” (para. 4.27, quoting Schacter). While Iran seemed to reject this contention at the time (para. 4.33), its missile exchanges with Israel in recent years arguably appear to embrace it (see Haque).

This does not mean all future attacks following completed ones should be viewed through the lens of immediacy. Serial attacks raise a proverbial chicken-or-the-egg problem, begging when imminence should “revive” and displace immediacy once one attack subsides and another is expected. To curb abuse, an appropriate limiting principle is that attacks should only be aggregated if they can be fairly characterized as part of the same overarching use of force, such as when they constitute a series or campaign. This conclusion finds support from the International Group of Experts that developed the Tallinn Manual 2.0. As they explain in the cyber context,

[A] cyber armed attack may commence with a wave of cyber operations against the victim State. The self-defence situation does not necessarily conclude with the termination of the cyber operations. If it is reasonable to conclude that further cyber operations are likely to follow, the victim State may treat those operations as a ‘cyber campaign’ and continue to act in self-defence. However, if such a conclusion is not reasonable, any further use of force … is liable to be characterized as mere retaliation. In the final analysis, the requirement of immediacy rests on a test of reasonableness in light of the circumstances prevailing at the time (commentary to rule 73, para. 13).

As the passages implies, the inquiry is contextual and fact driven. Much therefore depends on how one characterizes prospective attacks in relation to Iran’s conduct against Israel as a whole. Before turning to that analysis, however, a brief pause is in order to distinguish the jus ad bellum notion of an armed attack from that of an “armed conflict” under the law of armed conflict.

Armed Attacks and Armed Conflict

Whereas armed attacks trigger the right of self-defense under the jus ad bellum, the existence of an armed conflict triggers application of the law of armed conflict (also known as the jus in bello or international humanitarian law). Although both may regulate the conduct of States during warfare, they are distinct bodies of law. One accordingly has no legal bearing on the other. A State is not exempt from meeting the conditions for exercising self-defense simply because it is engaged in an armed conflict—just as it is not exempt from complying with the law of armed conflict merely because it may be a victim of aggression. In the context of Operation Rising Lion, therefore, strictly as a matter of law the only question to which the existence of an armed conflict is relevant is one of choice-of-law.

Nevertheless, although there is no causal relationship between the two, the two undeniably correlate and in many cases coincide. After all, force rising to the level of an armed attack often manifests from the military operations that give rise to an armed conflict (e.g., hostilities, invasions, occupations, etc.). Thus, as a matter of fact, that an armed conflict exists likely has some probative value on whether a series of attacks or campaign does as well. With this understanding in mind, the argument that the strikes in question were justified due to an ongoing armed conflict between Israel and Iran (see e.g., Corn and Kittrie; Cohen and Shany), which has been criticized due to its conflation with the jus in bello, may be reconcilable with approaching necessity through the criterion of immediacy.

Characterizing Iranian Attacks

There are likely reasonable arguments on either side of whether Iran’s attacks constitute a campaign for purposes of assessing the immediacy of Israel’s response. This is due, in part, to their varied and asymmetric character. They range from, for example, kinetic ballistic missile attacks, the last of which occurred months ago, to, some argue, Iran’s substantial involvement in ongoing attacks by non-State proxy groups. Nuclear weapons would further differ in degree, if not kind, from other attacks thus far.

But neither the manner of the attacks nor their consistency is a decisive factor. Instead, what binds operations into a campaign are their shared purpose or design. As other commentators have observed (e.g., here and here), drawing firm conclusions based on publicly available information is challenging. At the same time, to treat them as isolated events therefore feels a bit contrived and out of touch. It doesn’t take many leaps to reach a colorable argument that various Iranian attacks inextricably intertwine. One observer has suggested that at least some of Iran’s previous attacks on Israel could indeed reasonably comprise a campaign. In this regard, I share the sentiments of Professors Cohen and Shany, although made in a different context, in their recent Just Security post:

When viewed as a whole, we consider it somewhat artificial to neatly separate between the indirect proxy war and the direct Israeli-Iranian clashes, which emanated from the same proxy war, and between periods of direct clashes between Israel and Iran and waiting periods in which attacks “at the right time” are threatened. Such a compartmentalized and “revolving door” approach appears to obfuscate the ways in which the main protagonists see their relations with one another.

If this argument is correct, the diversity of Iran’s attacks on multiple fronts should not foreclose the possibility that they are part and parcel of an overarching campaign.

Nor should the fact that Iran does not currently possess nuclear weapons be fatal to the analysis. From an immediacy (in contrast to imminence) perspective, it matters not whether upcoming attacks in the series are expected to be executed by nuclear or other means. So long as additional attacks in the campaign are reasonably foreseeable and cannot be deterred otherwise, the use of force in self-defense remains necessary now, regardless of the mechanism(s) the aggressor intends to employ. The question of whether Israel may go so far as to target nuclear infrastructure to defend against those attacks becomes one of proportionality, a topic beyond the scope of this post.

Again, reasonable minds may disagree on how to characterize Iran’s various operations against Israel. But if one reasonably concludes they are part of a campaign of attacks, there is a valid argument that the timing of the Israeli operation was no impediment to its lawfulness.

Concluding Thoughts

The scholarly analyses of Operation Rising Lion are as varied in their approaches as they are in their conclusions. Considering the unsettled state of the law pertaining to necessity, I find many of them reasonable. But one should not easily overlook immediacy as a possible framework with which to view the current situation. This is particularly true for those who weigh heavily the existence of an ongoing Israeli-Iranian armed conflict, for it closely approximates that analysis while adhering to the language of the jus ad bellum.

It is not altogether clear through which lens, imminence or immediacy, Israel views the necessity of Operation Rising Lion. Its Article 51 notice to the Security Council states, “Operation Rising Lion was launched as a measure of last resort. It was prompted by a critical development in Iran’s covert nuclear weapons program and in response to, and in order to thwart, the threat of imminent Iranian attacks. This was the last window of opportunity to prevent Iran from acquiring nuclear weapons, and takes place after diplomacy proved ineffective.” This admittedly smacks of an imminence-driven assessment. On the other hand, the imminence of Iranian attacks would likely be a sufficient condition for self-defense under either criterion. The two are not mutually exclusive. Accordingly, one should not quickly discard immediacy as an approach to assessing the necessity of Israel’s action.

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Lieutenant Colonel W. Casey Biggerstaff is an Assistant Professor in the Department of Law and Philosophy at the U.S. Military Academy at West Point.

The views expressed are those of the author, and do not necessarily reflect the views or official position of the United States Military Academy, Department of the Army, Department of Defense or its components.

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Photo credit: IDF Spokesperson’s Unit