Expert Q&A: A Targeting Primer on the Iran War

The sustained U.S. and Israeli bombardment of Iran, and Iran’s response against not only those States, but also other States in the region, has generated a cascade of questions regarding how the law of armed conflict (LOAC) governs the hostilities. In this Q&A, we explain the LOAC rules that apply in many of the attacks that have drawn attention based on who or what appears to have been targeted, how the attacks took place, or their consequences. We begin by establishing that there is an international armed conflict to which LOAC applies. Discussion then turns to issues concerning the targeting of persons and objects, including at sea; specific weapons, the use of which is controversial; and targeting processes and limitations, including the rule of proportionality and the obligation to take precautions to minimize civilian harms in attack.

At the outset, it is essential to emphasize the foundational premise that runs through every answer: LOAC operates on the principle of equal application. That means the same set of rules binds all sides to the conflict without regard to which party had the legal right to resort to military force. Accordingly, whether the United States and Israel acted in lawful self-defense as they claim (Article 51 letters: Iran, U.S., Israel), or in violation of Article 2(4) of the UN Charter, which we believe to be the case, that question is entirely separate from–and has no bearing on–the obligations of the parties under LOAC.

I. The Applicable Law

Q 1. Does it matter whether the U.S. administration calls it a “war” for the law of armed conflict (LOAC) rules on targeting to apply?

Q 2. Do the same rules apply to States that started the war and States that are unlawfully attacked?

Q 3. May a State engage in operations that violate the LOAC rules governing attacks in response to the enemy’s violations?

II. Targeting Persons

Q 4. Who may be targeted during an armed conflict?

Q 5. Can civilians lose their protection from being targeted?

Q6.  Can political leaders be targeted?

Q 7. May law enforcement agencies and personnel be attacked?

III. Targeting Objects

Q 8. What objects may be attacked?

Q 9. What about strikes on the petroleum facilities?

Q 10: What about power plants and other power-related facilities?

Q 11. What about strikes on desalination facilities?

Q 12. What about strikes at or near facilities that are particularly hazardous, like nuclear sites?

IV. Naval Targeting (see here and here for in-depth analysis)

Q 13: Which types of ships are subject to attack?

Q 14: Can tankers carrying export oil be attacked on the basis that they are “war-sustaining” military objectives?

Q 15. Would sailing in convoy affect the targeting status of neutral warships or merchant vessels?

V. Weapons

Q 16. Is the use of cluster munitions, including in populated areas, lawful?

Q 17. Is the use of naval mines lawful?

VI. Targeting Processes and Limitations

Q 18. Are there other rules that protect civilians and civilian objects from being harmed during an attack?

Q19: How are attacks planned, and how are targets verified?

Q20: How is guidance provided to forces conducting attacks?

I. The Applicable Law

Q 1. Does it matter whether the U.S. administration calls it a “war” for the law of armed conflict (LOAC) rules on targeting to apply?

No. Following the U.S. and Israeli bombardment of Iran beginning on Feb. 28, the three States are unequivocally in an international armed conflict. As we explained in the context of U.S. military operations in Venezuela, the terminology used by political leaders has no bearing on the legal status of the conflict or the laws that govern it. In that case, we said an international armed conflict had commenced:

…regardless of how the United States might characterize the operations. Under Common Article 2 of the 1949 Geneva Conventions, the existence of an international armed conflict is a question of fact. In other words, if there are hostilities between the States, there is an international armed conflict even if one of them does not formally recognize its existence. Common Article 2 is universally accepted as reflective of customary international law.

Given the existence of hostilities between the United States and Israel on one side and Iran on the other, there is no plausible argument that the situation fails to qualify as an international armed conflict to which the law of armed conflict applies (see also DoD Law of War Manual, § 3.4.2).

In light of the existence of an international armed conflict, the customary LOAC rules on targeting apply fully. In treaty law, many of those rules are found in the 1977 Additional Protocol I to the Geneva Conventions. That instrument is not applicable in the conflict because key participants, including Iran, Israel, and the United States, are not Party to it. Still, its core provisions on targeting generally reflect customary international law binding on all States. 

Q 2. Do the same rules apply to States that started the war and States that are unlawfully attacked? 

Yes. As two of us have explained (with Mike Meier), the “equal application” principle is a fundamental cornerstone of the law of armed conflict (or IHL): 

A bedrock principle is that the laws of war apply equally to all belligerent parties. Both sides must comply with LOAC. That principle holds regardless of which side attacked first, whether the initial attack complied with international law, which side is acting in lawful self-defense, and irrespective of the relative justice of the causes involved.

In the terminology of international law, “whether a State is acting in violation of the prohibition on the use of force in Article 2(4) of the UN Charter or in individual or collective self-defense under Article 51 simply has no bearing on the law of armed conflict; its rules equally bind both the aggressor and the victim.” The United States has acknowledged this principle in its DoD (§ 3.5.2.1).

Q 3. May a State engage in operations that violate the LOAC rules governing attacks in response to the enemy’s violations?

Under only the most limited circumstances, which likely do not apply here. “Belligerent reprisals” are a highly constrained method of warfare in the law of armed conflict (see here). They are acts that would be unlawful but for the fact that they are taken in response to an adversary’s prior LOAC violation. Under customary international law, reprisals may not be engaged in for retaliation, revenge, or punishment; their sole purpose is to persuade the enemy to cease its own LOAC violations. Because reprisals involve actions that would otherwise amount to LOAC violations, they are subject to strict conditions. There must be an ongoing violation (no anticipatory reprisals); reprisals can only be taken as a last resort (after an exhaustion of other measures) in persuading the enemy to desist; they have to be proportionate to the unlawful acts to which they respond; they must be approved at a high level of authority; and they must be announced as reprisals given that their purpose is to dissuade the enemy from further unlawful conduct (DoD Law of War Manual, § 18.18). Reprisals must cease once that objective is achieved. Based on the publicly observed conduct of the parties involved in armed conflicts underway with Iran, it would be difficult to conclude that these conditions are met.

Moreover, certain categories of reprisals are categorically prohibited under customary international law. These include reprisals against individuals and entities protected by the 1949 Geneva Conventions, such as prisoners of war; the wounded, sick, and shipwrecked; medical personnel and units; and the population of occupied territories (DoD Law of War Manual, § 18.18.3.2). Although not applicable as such in this conflict, Additional Protocol I illustrates this reality by expressly prohibiting reprisals against a broad range of protected persons and objects, including civilians (art. 51(6)), civilian objects (art. 52(1)), cultural property (art. 53(c); see also Hague Cultural Property Convention), objects indispensable to the survival of the civilian population (art. 54(4)), the natural environment (art. 55(2)), and works and installations containing dangerous forces such as dams and nuclear electrical generating stations (art. 56(4)). We believe it is reasonable to argue that at least some of the prohibitions in Additional Protocol I regarding reprisals are now binding customary international law, although this remains contested, and the question of whether any States might qualify as persistent objectors remains.

II. Targeting Persons

Q 4. Who may be targeted during an armed conflict?

The starting point is the core LOAC principle of distinction: parties to an armed conflict must always distinguish between combatants and civilians and may target only the former, with the limited exception explained in the question below (on direct participation in hostilities).

During an international armed conflict, members of a State’s armed forces may be attacked at any time solely based on their status (so-called “status-based targeting”), unless they are hors de combat (captured, surrendered, or wounded). Armed forces include not only the regular military–such as the armed forces of all States involved, including the Iranian armed forces and Revolutionary Guard Corps, but also militia and volunteer groups that are part of those forces. This includes units of the Basij tasked with supporting military operations, especially of the IRGC. It is also widely accepted that members of “organized armed groups” are targetable on the same basis as members of the armed forces (DoD Law of War Manual, § 5.7.3), although there is disagreement over whether this includes all members of the group or only those with a “continuous combat function.”

Conversely, civilians are all persons who do not belong to these categories. They may not be directly attacked, must be considered in the proportionality analysis during attacks on combatants and military objectives, and feasible precautions have to be taken to avoid harming them (DoD Law of War Manual, §§ 5.11, 5.12).

Q 5. Can civilians lose their protection from being targeted?

Yes, but only under the specific circumstances we explain here. Civilians lose their protection from attack only “for such time as” they directly participate in hostilities (DoD Law of War Manual, § 5.8). Direct participation involves conduct intended to harm the enemy’s military operations or capacity, or that directly contributes to such harm. Crucially, there must be a direct causal link between the act and the harm, meaning the conduct must be closely related to the military operation that is likely to produce military effects; general or indirect contributions do not suffice.

Examples of direct participation include conducting attacks, operating weapon systems, relaying target intelligence, guiding forces to a target, transporting weapons to frontline fighters (or “an active firing position”), or acting as a lookout or spotter during an operation (DoD Law of War Manual, § 5.8.3.1). More remote activities, such as involvement in general war production, political support, or economic contributions, do not meet this threshold. Individuals directly participating in hostilities are only subject to attack during their period of participation, although there is significant controversy over how to define that period, especially when the conduct is recurring.

Q6.  Can political leaders be targeted?

Not unless they independently qualify as combatants or directly participate in hostilities. Political leaders are not lawful targets simply by virtue of the office they hold. In the law of armed conflict, the decisive question is whether the individual qualifies as a member of the armed forces or, if not, is a civilian who is directly participating in the hostilities (see Mike’s and Marko Milanovic’s analysis).

Clearly, military leaders may be attacked. In Iran, the armed forces include not only the regular army (Artesh) but also the Islamic Revolutionary Guard Corps (IRGC), an integral component of Iran’s armed forces. Individuals who are members of these institutions are targetable based on their status. This would include political leaders who formally occupy positions in the armed forces and exercise command authority over operations.

Political leaders who are not members of the armed forces may not be made the object of attack based on their status. Instead, like other civilians, they may be targeted only “for such time” as they “directly participate in the hostilities” (see Q5). In the leadership context, making specific operational or targeting decisions, issuing orders for specific attacks, or otherwise exercising operational authority over military forces engaged in hostilities would clearly qualify. Such direct participation is often framed as participating at the tactical or operational levels of war.

This approach is reflected in the DoD Law of War Manual: “Leaders who are not members of an armed force or armed group (including heads of State, civilian officials, and political leaders) may be made the object of attack if their responsibilities include the operational command or control of the armed forces. For example, as the commander-in-chief of the U.S. armed forces, the President would be a legitimate target in wartime, as would, for example, the Prime Minister of a constitutional monarchy” (§ 5.7.4).

By contrast, general political decision-making–like setting national strategy, approving military budgets, or articulating war aims–does not amount to direct participation in the hostilities. The test is a functional one that draws a line between political authority, on the one hand, and military command and operational participation, on the other. Those political leaders who are not direct participants in hostilities retain their protections as civilians under LOAC, regardless of their prominence or influence. In the current conflict, it appears to us that the reported intent to target Iran’s Parliamentary speaker Mohammad-Bagher Ghalibaf and Foreign Minister Abbas Araghchi (reportedly suspended from the list of targets on Pakistan’s request at the time of writing) would be unlawful based on their status – that is, absent clear information of direct participation in hostilities, they remain civilians who must be protected from attack as such.

Former political leaders, including those who qualified as members of the armed forces or directly participated in hostilities in the past, may only be attacked if and when they subsequently participate in the current hostilities. Future leaders may not be targeted prospectively – they would become targetable only if they assume a position in the armed forces or, as civilian leaders, directly participate in the hostilities, for such time as they do so. 

Q 7. May law enforcement agencies and personnel be attacked?

Not unless they are incorporated into the armed forces or directly participate in hostilities. Law enforcement personnel are generally considered civilians under the law of armed conflict and, therefore, protected from direct attack (DoD Law of War Manual, § 4.23). However, if they are incorporated into the armed forces during an international armed conflict through domestic law, command arrangements, or operational integration, their members assume the status of combatants. They may be targeted on that basis alone.

Even where law enforcement personnel are not incorporated into the armed forces and remain civilians, they are targetable for such time as they directly participate in hostilities (see Q5). Examples include engaging in combat operations and gathering actionable intelligence for use by the military.

Of significance in the current conflict, the ICRC’s project on direct participation in hostilities concluded that civilians who “inflict death, injury, or destruction on persons or objects protected against direct attack” under the law of armed conflict may be treated as direct participants in the hostilities, thus losing their protection from attack. All members of the international expert group who participated in the project (including Mike) agreed with this proposition.

III. Targeting Objects

Q 8. What objects may be attacked?

Only “military objectives,” a legal term of art, may be attacked. Under the law of armed conflict, military objectives are “objects which, by their nature, location, purpose or use make an effective contribution to military action and whose partial or total destruction, capture or neutralization, in the circumstances ruling at the time, offers a definite military advantage” (DoD Law of War Manual, § 5.6.3; see also Additional Protocol I, art. 52(2); U.S. State Department Legal Adviser statement). This is a two-pronged test in which there must be both a sufficient nexus between the object and military action, and the attack on the object has to result in a military advantage that is more than speculative.

The four categories of objects that can make an “effective contribution” operationalize the definition. Objects are military objectives by “nature” when they are inherently military, such as weapons systems, military vehicles, military aircraft, warships, and command-and-control facilities. Civilian objects become military objectives by “location” if their geographic position makes them militarily significant, as with structures that offer a tactical advantage, like a high point for observation or a maneuver choke point. Objects qualify by “purpose” based on their intended use. An example is a civilian building being converted for military use by equipping it with military communications capabilities and hardening it against attack. Finally, civilian objects are transformed into military objectives by “use” when employed for military ends, as in the case of an apartment building that houses troops or stores munitions, or civilian communications assets used to transmit military orders and intelligence.

It is essential to understand that the analysis is contextual. For instance, a facility that was used by the armed forces but is no longer so used, and for which there is no indication that it will be in the future, reverts to civilian status. (This is the case, for example, with the Shajarah Tayyebeh girls’ elementary school in Minab, struck by a Tomahawk missile on the first day of the war, which had – many years prior – been an IRGC facility but was undeniably civilian at the time of the strike.)

Q 9. What about strikes on the petroleum facilities?

They are lawful only if they satisfy the requirements to qualify as a “military objective” (see Q8), and the rules of proportionality and precautions in attack, among others, are also met. Like other normally civilian objects, petroleum facilities may become military objectives by virtue of their present or future use (purpose). Because oil production, refining, and distribution infrastructure serve civilian economic and energy needs in most cases, the burden falls on the attacker to demonstrate that a particular facility meets the military objective requirements, based on reliable, context-specific information.

At the same time, petroleum facilities are often described as so-called “dual-use” objects, meaning they serve both civilian and military functions. For example, fuel infrastructure can supply the armed forces (military vehicles, aircraft, warships, etc.) while also supporting civilian life, industry, and transportation. Under the law of armed conflict, such facilities become lawful targets if they make an effective contribution to military action, which in such cases they do, and damaging or destroying them will afford the attacker a “definite military advantage.”

As the DoD Law of War Manual cautions, in such cases “it will be appropriate to consider in applying the principle of proportionality the harm to the civilian population that is expected to result from the attack on such a military objective” (§ 5.6.1.2). That harm would include injury or death of civilians, including workers at the facility, and damage to any separate components of the facility having no military use or nearby civilian objects. It would also include other reasonably foreseeable effects harming the civilian population, as well as excessive “incidental damage to the environment.”

Even if a petroleum facility constitutes a military objective and an attack on it would not violate the proportionality rule, the attacker is independently required to take feasible precautions to avoid or minimize harm to civilians or civilian objects. Moreover, if the attack “may cause severe damage to the civilian population and the natural environment,” the special protections applied to dangerous forces are merited (see Q 8).

A more controversial theory is that petroleum facilities may be targeted as so-called “war-sustaining” objects on the basis that they generate revenue that supports the enemy’s war effort. The DoD Law of War Manual asserts that “[e]conomic objects associated with military operations or with war-supporting or war-sustaining industries have been regarded as military objectives” (emphasis added). As examples, it points to “oil refining and distribution facilities, and objects associated with petroleum, oil, and lubricant products (including production, transportation, storage, and distribution facilities)” (§ 5.6.8.5). This approach is not universally accepted, and many States and commentators (including Mike and Tess) take the view that the law of armed conflict requires a more direct nexus to military action than a general economic contribution. Accordingly, while petroleum facilities may in some circumstances qualify as lawful targets—particularly where they directly support military operations—their targeting on a purely “war-sustaining” basis remains legally contested.

What’s more, as Lieutenant Colonel W. Casey Biggerstaff wrote, even on the view that war-sustaining objects can be targetable in some circumstances, that “does not displace the requirement that a military objective exhibit a discernable causal connection to enemy military action;” there is no rule that petroleum facilities per se may be targeted; and economic resources “do not qualify as military objectives merely because they contribute to the overall pool of resources available to its adversaries.”

Q 10: What about power plants and other power-related facilities?

Electric power infrastructure, including generation plants, transmission systems, and substations, is generally regarded as civilian in character and therefore protected from attack unless it satisfies the definition of a military objective (see Q 8). That determination depends on whether the facility, in the circumstances ruling at the time, makes an effective contribution to military action and whether its destruction offers a definite military advantage. In most situations, electricity systems are integral to civilian life—supporting hospitals, water distribution, sanitation, basic economic activity, and day-to-day life—which weighs heavily against their targeting absent a clear and concrete military connection.

That said, power-related facilities often function as dual-use objects. Electricity may directly support military capabilities such as command-and-control systems, air defense networks, weapons production factories, and the operation of military facilities. Historical practice likewise reflects that electrical power infrastructure has been targeted when doing so would degrade an adversary’s military effectiveness. But it must be emphasized that power infrastructure can be struck only when it offers a “definite military advantage;” it is not permissible to attack it absent a clear military rationale.

Even where a power facility satisfies the military objective test, attacks on it are tightly constrained by the rules of proportionality and precautions in attack (see Q 18). Electrical systems are typically interconnected, meaning that damage to one component can have widespread and foreseeable effects on the civilian population, including, for instance, cascading impacts on water and food supply, healthcare, public health, and emergency response capability. Such foreseeable consequences must be assessed in advance under the proportionality rule, and those planning or executing the attack must take all feasible measures to mitigate harm, such as limiting the scope of the strike; selecting particular components of the power system; selecting weapons likely to cause less physical damage or sickness, injury, or death; or striking a different target altogether that will yield the desired effect on the enemy’s military capability.

Q 11. What about strikes on desalination facilities?

Because desalination facilities are so closely tied to the provision of water essential to civilian life, attacks on them face significant legal constraints; they are difficult to justify under the law of armed conflict. Desalination facilities are, as a starting point, civilian objects and may be targeted only if they have become military objectives—that is, if, through their use, they make an effective contribution to military action and their destruction offers a definite military advantage (see Q 8). In most cases, desalination plants are used to produce potable water for the civilian population, which augurs against their characterization as military objectives. Only in limited circumstances, as when a facility is directly supporting enemy military forces, could it become a lawful target. Even then, the rules of proportionality and precautions (see Q 5) would apply to the extent their loss affected civilian health. Foreseeable effects on civilian populations are particularly acute in the current conflict, given that many of the countries involved have extraordinarily arid climates and rely on desalination as a vital water supply.

The customary law prohibition on starvation also bears on the targeting of desalination plants. As noted in the Department of Defense Law of War Manual, “Starvation specifically directed against the enemy civilian population, however, is prohibited. For example, it would be prohibited to destroy food or water supplies for the purpose of denying sustenance to the civilian population” (§ 5.20.1; see also ICRC, Customary International Humanitarian Law, rules 53, 54). Thus, a strike on a desalination facility violates the prohibition if undertaken with the intent of denying water to the civilian population. However, even where there is no such intent, the foreseeable effects of disrupting a major source of potable water—such as dehydration, disease, and cascading humanitarian consequences—must be accounted for in applying the rules on proportionality and precautions in attack.

Although not applicable as such in this conflict, it merits note that Additional Protocol I (1977) expressly prohibits attacks on objects indispensable to the survival of the civilian population, including drinking water installations and supplies (art. 54). Desalination facilities, particularly in water-scarce regions, clearly qualify as “objects indispensable” because their destruction or damage can have immediate and widespread effects on access to drinking water (“water, and the systems by which they are produced and supplied are… understood as intrinsically indispensable”). This provision reflects a broader concern—also evident in the customary law cited above—that infrastructure necessary to provide water to civilians warrants especially careful consideration in targeting decisions. (For a thoughtful analysis on targeting objects indispensable to civilian survival, see Tom Dannenbaum’s work here).

Q 12. What about strikes at or near facilities that are particularly hazardous, like nuclear sites?

Facilities such as nuclear power plants and other so-called “works containing dangerous forces,” like dams or facilities producing weapons of mass destruction, are usually civilian objects. They may be attacked only if they qualify as military objectives because they make an effective contribution to military action and their destruction offers a definite military advantage. In such cases, they are subject to the same customary LOAC rules as other military objectives, including the rule of proportionality and the requirement to take precautions in attack to minimize civilian harm. However, because damage to them could release dangerous forces, such as radiation or flooding, and cause severe and widespread civilian harm, they are afforded particular consideration in practice. In particular, the foreseeability of catastrophic effects well beyond the immediate target requires careful analysis of the potential for incidental injury to civilians and collateral damage to civilian objects.

While not applicable to this conflict, Additional Protocol I illustrates the heightened concerns about striking such targets. Article 56 prohibits attacking dams, dykes, and nuclear electrical generating stations, even if they are military objectives, if the attack may cause the “release of dangerous forces and consequent severe losses among the civilian population.” It further extends protection to military objectives located at or near such installations when attacking them could produce the same effects. The protection may cease only in narrowly defined circumstances, such as when the installation provides regular, significant, and direct support to military operations and an attack is the only feasible means of terminating that support. Article 56 reflects a broader humanitarian concern, one also evident in customary law, that strikes at or near nuclear facilities are subject to exceptionally high legal scrutiny (see ICRC Customary IHL study, Rule 42: “Particular care must be taken… to avoid the release of dangerous forces and consequent severe losses among the civilian population.”).

The Department of Defense’s Law of War Manual reflects this approach, while rejecting any categorical immunity for such facilities. It recognizes that facilities containing dangerous forces may be attacked if they are military objectives, for instance, to deny “electric power to military sources” or “use of a dangerous facility (e.g., by causing release from a dam) to damage or destroy other military objectives.” However, the manual also cautions that “[i]n light of the increased potential magnitude of incidental harm, additional precautions, such as weaponeering or timing the attack such that weather conditions would minimize dispersion of dangerous materials, may be appropriate to reduce the risk that the release of these dangerous forces may pose to the civilian population” (§ 5.13).

IV. Naval Targeting (see here and here for in-depth analysis)

Q 13: Which types of ships are subject to attack?

As in land warfare, only military objectives may be attacked at sea. Warships are military objectives by nature and may be targeted on that basis alone. The same is true of naval auxiliaries, which are vessels that do not qualify as warships (e.g., they have a civilian, rather than commissioned, master) but are owned or controlled by the armed forces and used for military purposes, such as transporting troops, supplies, or fuel in direct support of military operations.

By contrast, merchant vessels and other civilian ships are protected from attack unless and until they become military objectives by virtue of their use or conduct. For example, they qualify as military objectives if they are carrying military material, transmitting intelligence, or otherwise making an effective contribution to military action.

How civilians aboard merchant or civilian vessels that qualify as military objectives are to be treated in the proportionality assessment remains unsettled in the law of naval warfare. As noted in the  Newport Manual on the Law of Naval Warfare, “[a]ccording to one view, the presence of passengers on board a vessel qualifying as a lawful target does not require a collateral damage assessment. An opposite view would require an assessment to be conducted if there are passengers on board the target vessel” (§ 8.8.1). Although the former is the traditional platform-based approach in the law of naval warfare, we are of the view that the latter is more defensible in contemporary warfare. Indeed, the DoD Law of War Manual adopts it for civilian passenger vessels (§ 13.5.2.1).

Q 14: Can tankers carrying export oil be attacked on the basis that they are “war-sustaining” military objectives?

This is contested. There is a division of opinion on whether objects that sustain a State’s war effort economically, such as tankers transporting oil for export, may be targeted (see Q 9). Some States, most notably the United States, have adopted a broad interpretation according to which “war-sustaining” objects may qualify as military objectives (DoD Law of War Manual § 5.6.6.2). The contrary view is that the law of armed conflict requires a more direct nexus to military action. By this approach (which Mike and Tess share), oil tankers are not targetable merely because they generate revenue for the enemy’s military forces. Rather, they would become lawful targets only if they were making an effective contribution to military operations such as directly supplying fuel to enemy forces. In the absence of such a connection, they remain civilian objects that are not subject to attack on this view.

Q 15. Would sailing in convoy affect the targeting status of neutral warships or merchant vessels?

Yes, “convoying” can significantly alter the legal status of vessels under the law of naval warfare. If neutral warships escort neutral merchant vessels, the vessels in the convoy retain neutral status and benefit from immunity from visit and search, provided the escorting commander certifies the neutral character and cargo of the vessels (NWP 1-14M, § 7.6).

The situation changes when the convoy becomes associated with a belligerent, as the escorting warships determine the convoy’s character. Thus, where neutral merchant vessels are escorted by belligerent (e.g., U.S.) warships, they may be treated as part of a belligerent convoy and become liable to attack as military objectives (NWP 1-14M, § 8.6.2.2). This aligns with the broader rule that merchant vessels may be attacked when they are incorporated into or directly supporting enemy military operations. The same logic applies if neutral warships operate alongside belligerent warships in a coordinated escort role, thereby aligning themselves with one party’s military effort. Both the neutral warships and escorted neutral merchant vessels are subject to attack as military objectives.

Finally, where neutral warships escort belligerent merchant vessels or otherwise interfere with lawful belligerent rights—such as resisting visit and search—they risk crossing from neutrality into participation in the hostilities. In such circumstances, the neutral warships may lose their protected status (NWP 1-14M §§ 7.5, 7.6), and both the escort and escorted vessels may be treated as military objectives. In short, while neutral convoying is recognized in a limited sense, sailing in convoy with or in support of a belligerent can transform the legal status of vessels, exposing them to attack under the law of naval warfare.

V. Weapons

Q 16. Is the use of cluster munitions, including in populated areas, lawful?

The 2008 Convention on Cluster Munitions prohibits the use, stockpiling, and transfer of such weapons, but key States involved in this conflict, including Iran, the United States, and Israel, are not Parties and are not bound by its provisions. The United States has taken the position that the Convention does not reflect customary international law and does not establish a general prohibition on cluster munitions (DoD Law of War Manual, § 6.13.4), a position shared by Israel and Iran.

This being so, the question in this conflict is whether their use in a particular circumstance is consistent with the general rules governing the conduct of hostilities. These include the principles of distinction (here and here), including the prohibition on indiscriminate attack, the rule of proportionality, and the requirement to take precautions in attack to minimize harm to civilians and civilian objects (Q 18; DoD Law of War Manual, §§ 5.4.3.2, 5.11, 5.12).

It is extremely difficult to justify most uses of cluster munitions under these rules because they disperse submunitions over a wide area and may result in unexploded ordnance that can be dangerous to civilians for years after the attack. As a result, their use in densely populated urban areas will almost always be indiscriminate or cause disproportionate collateral damage to civilian objects or incidental injury to civilians. The United States, for example, received assurances from Ukraine that it would not use U.S.-supplied cluster munitions in civilian-populated urban environments. (Indeed, the use of other types of explosive weapons in densely populated areas also raises heightened concerns, and the United States in 2022 endorsed a Declaration on “Strengthening the Protection of Civilians from the Humanitarian Consequences arising from the use of Explosive Weapons in Populated Areas”).

In many cases, using weapons other than cluster munitions will pose less risk to civilians while achieving a comparable military advantage. If the use of other weapons is feasible in the circumstances, using cluster munitions would be unlawful. Accordingly, in many operational contexts, it will be extremely difficult to employ the weapons lawfully. For this reason, the Department of Defense has imposed strict restrictions on their use (DoD Law of War Manual, § 6.13.3).

Q 17. Is the use of naval mines lawful? 

Naval mines are not prohibited per se, but their use is regulated by the customary law of naval warfare and by treaty, notably the 1907 Hague Convention VIII on automatic submarine contact mines, which is generally considered reflective of customary law binding on all States. These rules impose operational constraints designed to limit the potential indiscriminate effects of mines.

For example, they prohibit laying unanchored (drifting) mines unless they are designed to become harmless within a short period after control is lost. And anchored (moored) mines must automatically become harmless if they break loose from their moorings. More broadly, belligerents laying mines are required to pay due regard for the safety of commercial shipping and, where feasible, must provide notification of the location of minefields and remove or render them harmless when hostilities end. These technical requirements exist alongside the general LOAC rules regarding distinction, proportionality, and precautions in attack. In congested waterways such as the Strait of Hormuz, compliance with these rules is especially demanding given the heightened risk to neutral vessels and civilian shipping.

Iran’s reported laying of naval mines in the Strait of Hormuz, together with the effective halting of traffic through a narrow waterway heavily used by neutral shipping, and its failure to provide the requisite notification to shipping, cannot be reconciled with the requirement to pay due regard to civilian and neutral navigation and with the general prohibition on indiscriminate methods of warfare in such a congested maritime corridor. The concern is even sharper in light of reports that an Iranian Defence Council statement threatens to cut Gulf routes by laying “sea mines, including floating mines,” which directly implicates the rule against employing drifting mines unless they are designed to become harmless shortly after control is lost.

VI. Targeting Processes and Limitations

Q 18. Are there other rules that protect civilians and civilian objects from being harmed during an attack?

Yes. A primary purpose of the treaty and customary LOAC governing the “conduct of hostilities” is to spare the civilian population from the effects of war (DoD Law of War Manual, § 5.2). A key protection beyond the prohibition on directly attacking civilians and civilian objects is the rule of proportionality (see Q 9), which prohibits attacks in which the expected incidental loss of civilian life, injury to civilians, or damage to civilian objects would be excessive in relation to the concrete and direct military advantage anticipated from the attack (DoD Law of War Manual, § 5.12; Additional Protocol I, arts. 51 and 57).

As noted in the  DoD Law of War Manual, “[d]etermining whether the expected incidental harm is excessive does not necessarily lend itself to quantitative analysis because the comparison is often between unlike quantities and values” (§ 4.23). Rather, it requires a good-faith, highly context-dependent judgment made before the attack as to whether the harm caused to civilians will be “excessive.” For instance, killing a high-value target such as a senior military leader will allow for greater incidental civilian injury or death or damage to civilian property than killing a low-level fighter. Moreover, the evaluation is made by those who plan, approve, and execute the attack and is based on the information reasonably available to them at the time.

Importantly, the question of what types of harms qualify as “incidental harm” that must be factored into a proportionality assessment is somewhat contested. However, incidental civilian death or injury, and damage to civilian objects must be included in the analysis. Speculative effects that are not reasonably foreseeable need not be included. Likewise, “[m]ere inconvenience or temporary disruptions to civilian life” need not be factored into the proportionality calculation (DoD Law of War Manual, § 5.12.1.2). That said, reasonably foreseeable effects are not speculative; they must be weighed in a proportionality analysis, and the commander must include such effects in a proportionality analysis even if they are “indirect.”

Closely related is the obligation to take precautions in attack, which operationally is a significant practical constraint on military operations. Attackers must take all feasible measures to verify that targets are lawful military objectives and have to consider feasible alternatives—including different targets, timing, tactics, or weapons—that would achieve the desired military advantage while reducing the risk of civilian harm (DoD Law of War Manual, § 5.11; Additional Protocol I, art. 57). Additionally, attackers must effectively warn the civilian population if it will be affected by the attack. Doing so is required when the circumstances permit, as when surprise is not an element of the attack and the target is fixed (e.g., a building).

Although the United States does not accept the premise (DoD Law of War Manual, § 5.2.3.5), the ICRC and some experts assert that there is a customary law obligation for attackers to exercise “constant care” to “spare” civilians and civilian objects, a broad obligation that requires them to consider the impact of their operations on the civilian population. We agree.

Q19: How are attacks planned, and how are targets verified?

We cannot speculate as to the specific planning and verification processes used in the current war with Iran, but what follows is an overview of how these processes would typically work. The targeting process (see NATO AJP 3-9 and here) begins with the campaign’s objectives and desired end state, which drive the selection and prioritization of potential targets. Planners then develop targets through a detailed analysis of the operational environment, including the adversary’s defensive capabilities. An assessment of the attacker’s own capabilities follows, including the available means and methods of attack, both lethal and non-lethal, along with their expected effects and anticipated civilian harm. The information generated supports the commander’s decision on whether to approve a strike, after which detailed mission planning and execution occur. Post-strike assessment of the results informs subsequent strikes.

Target verification is a continuous requirement throughout this process. During target development, proposed targets are vetted and validated, including through legal review, to determine whether they qualify as lawful military objectives and whether their engagement would be consistent with applicable law and rules of engagement. Validation does not itself authorize attack; rather, it reflects a determination that, based on available intelligence, the target may lawfully be engaged.

The obligation to verify continues through execution, requiring forces to do everything feasible to confirm the target’s status, including achieving identification at an appropriate standard before engaging.

Deliberate (planned) targeting and dynamic targeting have to be distinguished. Deliberate targeting addresses known targets and typically occurs hours or days in advance, allowing for extensive intelligence collection, legal review, and capabilities analysis. Dynamic targeting, by contrast, involves targets of opportunity or emerging threats that must be engaged on much shorter timelines, often in rapidly evolving operational conditions. Although the timeframe is compressed, the same legal standards apply.

Verification in both deliberate and dynamic targeting relies on a range of systems and methods designed to reduce uncertainty. Intelligence, surveillance, and reconnaissance (ISR) assets—such as satellites, unmanned aerial systems, signals intelligence, and human sources—are used to identify and monitor targets through the “find, fix, track, target, engage, and assess” stages of the operation. Analysts may use open-source information alongside employing techniques such as pattern-of-life analysis, geolocation, and multi-source corroboration to meet the identification standards. During execution, operators maintain situational awareness—often through real-time sensor feeds—to confirm that the target remains lawful and that circumstances have not changed. Even in dynamic targeting, where decisions must be made quickly, these systems support the ongoing legal assessment.

Q20: How is guidance provided to forces conducting attacks?

Guidance to forces conducting attacks is provided through a layered system of command direction that translates legal obligations into operational requirements (see Cherry, Tinkler, Schmitt). At the highest level, the commander’s intent and operational guidance establish how force is to be used in the campaign, including the degree of risk to civilians that will be accepted and the priority placed on minimizing harm (with the baseline, of course, that they must be consistent with LOAC obligations at a minimum).

This guidance is then implemented through instruments such as rules of engagement (ROE), fragmentary orders, and tactical directives, which specify when, where, and how force may be employed (see JP 5-0, Joint Planning). ROE, in particular, often incorporate both legal requirements and policy constraints, and may be more restrictive than the law of armed conflict—for example, by limiting the categories of targets that may be engaged, requiring higher levels of approval for certain strikes, or restricting the use of particular weapons systems in populated areas (see Army Operational Law Handbook, ch. 5).

At a more detailed level, targeting-specific tools and processes operationalize this guidance. Militaries employ no-strike lists (NSLs) to identify protected persons and objects—such as medical facilities, schools, and cultural property—that are presumptively off-limits absent exceptional circumstances. They also use restricted target lists (RTLs) to identify otherwise lawful military objectives that require additional scrutiny or higher-level approval before engagement due to the risk of significant civilian harm or strategic consequences. These lists are integrated into the targeting process alongside requirements for identification and collateral damage estimation, ensuring that those planning and executing attacks assess both the target’s status and the expected effects of the strike. Together, these mechanisms function to guide operational decision-making in a way that gives concrete effect to the principles of distinction, proportionality, and precautions in attack.

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