Rules of Engagement in Large-Scale Combat Operations: Force Enabler or Much Ado About Nothing?
Rules of Engagement (ROE) have traditionally played a major role in the execution of military operations, particularly when a given situation has not reached the threshold of armed conflict. In more recent years, however, some military operations have used ROE to cover the use of force in armed conflict, including the International Security Assistance Forces’ operation in Afghanistan, Operation Unified Protector in Libya, and Operation Inherent Resolve against the Islamic State in Iraq and Syria.
Recent State practice indicates that more restrictive peacetime ROE have now found their way to cover not only military operations other than war (MOOTW), but also wartime situations. As one scholar pointed out, “Rather than differentiating between types of operations, NATO applies the more restrictive approach to all operations when drafting ROEs” (p. 11). However, the application of these more restrictive ROE in the context of counterterrorism/counterinsurgency operations has given rise to friction and controversy (e.g., here, here, and here).
This new practice of applying restrictive ROE sets in times of armed conflict raises challenging questions as to their role and scope in the conduct of large-scale combat operations (LSCO). While ROE may be the ideal tool to regulate the use of force when hostilities have not yet reached the threshold of armed conflict, restrictively construed ROE regulating when, where, how, and against whom belligerents may use force can obstruct mission accomplishment in times of armed conflict.
The implementation of restrictive ROE, based on a law enforcement paradigm, is inconsistent with the requirement of military necessity during armed conflict. Moreover, and as I will explain in the following paragraphs, doing so leads to legal flaws which some States and coalitions have officially incorporated into their doctrine (e.g., NATO’s Allied Joint Doctrine for Joint Targeting (AJP-3.9).
The Legal Framework
Military leaders do not draft ROE in a legal vacuum. National and international law govern the conduct of military operations. While domestic and international human rights law (IHRL), with or without derogations, regulate MOOTW, the law of armed conflict (LOAC) applies in situations of international or non-international armed conflict. To reflect the appropriate legal framework regarding the use of force policy, it is of the utmost importance to ensure all planning documents—in particular the Concept of Operations (CONOPs) and the (OPLAN)—include adequate provisions to this end. Indeed, commanders cannot view ROE in isolation or separated from the operational planning process.
The ROE must reflect these military and legal considerations to allow mission accomplishment. In other words, as soon as a situation becomes an armed conflict, military operations are governed by LOAC. When LOAC is not applicable, the use of force against persons and objects remains regulated by domestic law and IHRL.
ROE in Situations Other than Armed Conflict
During MOOTW, all use of force in self-defence or pursuant to promulgated ROE must conform with international law, in particular with IHRL. The concordant ROE set must therefore incorporate IHRL’s limitations.
In general, the OPLAN must contain the following wording:
The use of force must be limited and proportional to the level of threat presented/perceived.
The degree of force must be no more than necessary to carry out duties and accomplish assigned objectives of the mission.
The specific Annex E (on the use of force) to the OPLAN, must then define the notions of “necessity” and “proportionality” as applicable for the duration of the operation (here). For example:
“Necessity” means that “the use of force be the last resort after other means (e.g. warnings) have failed or are judged unavailable/ineffective.”
“Proportionality” means that “the force used must be commensurate with the threat posed,” or “generally phrased in terms of the use of minimum force limited in intensity, and duration, so as to be proportionate to the perceived threat.”
ROE must limit the loss of life, injury, or damage because of the use of force to the degree, intensity, and duration necessary to eliminate the threat. The commander must then promulgate the numbered ROE list for the operation in the form of authorisations, limitations, or restrictions. For example:
ROE AAA: The use of minimum force, excluding deadly force, to [BLANK] is authorized.
ROE BBB: The use of minimum force, up to and including deadly force, to [BLANK] is prohibited.
NATO’s Glossary of Terms and Definitions (AAP-6), defines “minimum force” as “force, up to and including deadly force, limited to the degree, intensity and duration necessary to achieve the objective” (p. 84). This definition fully complies with the applicable IHRL legal regime regulating the use of force in peacetime operations. Indeed, military forces resorting to the use of lethal force under the law enforcement paradigm act on the basis of national laws and doctrines, ROE, and other legislative or executive instruments that fully reflect the requirements of absolute necessity, strict proportionality, and protection of the right to life under IHRL. This clearly distinguishes such uses of force from force used during the conduct of hostilities.
While an ROE profile based on the use of “minimum force” makes sense when operations take place in MOOTW, integrating peacetime ROE profiles into LSCO becomes highly problematic. First, doing so jeopardizes mission accomplishment by imposing legal standards on military commanders and units that are not justified by law. Second, the application of peacetime legal standards contaminates targeting and ROE rules. As E.W. Pouw wrote, “In sum, IHRL offers only a very limited permissible scope for targeting, which, as a rule, is prohibited, and may only be resorted to in exceptional circumstances” (p. 254).
Another important contention in issuing peacetime ROE relates to the use of force against persons engaging in the commission of a hostile act (HA) or demonstrating a hostile intent (HI). States introduced HA/HI ROE to fill the gap between the expansive definition of self-defence under U.S. legislation and the more restrictive definitions thereof in European States. However, the extent to which the use of force under these HA/HI ROE will be compatible with IHRL’s rules on the right to life remains doubtful, as IHRL requires any use of force to be in response to the manifestation of a concrete and specific threat. This issue is very complex and is beyond the scope of this post.
ROE in Times of Armed Conflict
In times of armed conflict, the applicable legal framework for establishing ROE is LOAC. This means the use of force against an adversary must comply with distinction, precautions in attack, and proportionality. In LOAC contexts, terms like “proportionality” and “necessity” require precise definitions. While “proportionality” under IHRL refers to proportionality between the threat and the response to that threat (see above), proportionality under LOAC refers to the relationship between, on the one hand, the expected incidental damage to civilians, civilian objects, and the civilian population versus, on the other hand, the anticipated direct and concrete military advantage of the attack (Additional Protocol I (AP I), arts. 51(5)(b), 57(2)).
Unfortunately, current operational practice reveals that military planners and legal advisors continue to apply the more restrictive IHRL definitions in situations of armed conflict. States should categorically reject this approach. Not only does such a restrictive ROE profile adversely influence the commander’s ability to execute his mission, it also undoubtedly affects the soldier’s decision to use necessary force.
To successfully conduct LSCO in times of armed conflict, the only necessary ROE is the well-known offensive, 42X-series “attack” ROE authorizing the use of lethal force against declared hostile forces, including civilians who directly participate in hostilities. States should likewise reject ROE profiles that do not distinguish between peacetime (“use of minimum force”) and wartime ROE (“attacks”), which are legally wrong and operationally counterproductive. Although operational and/or policy considerations may limit ROE, even in times of armed conflict, military planners can easily integrate these considerations into the OPLAN (e.g., in the “constraints and restraints” paragraph).
Two other factors compound the ROE confusion. First, LOAC-attack ROE allow military forces to use lethal force against designated hostile forces (persons and objects). Combining IHRL’s “minimum force” ROE with LOAC’s “attack” ROE against hostile forces in one ROE profile leads to confusion over when combatants are authorized to initiate lethal contact, particularly when the IHRL ROE are based on HA/HI. This discussion is not merely academic, as correctly emphasized by Professor Garraway:
Whilst all this is of great interest to academics, it does not assist the soldier on the ground faced with an instant decision on whether or not to open fire. Of course, his decision will be instinctive—it has to be—but that instinct will be based on hours of training carried out before deployment. The trainers have to think more deeply into these matters. What is the test that the soldiers need to apply? What questions should he be asking himself, almost certainly unconsciously, as he makes that split-second decision (p. 502)?
Second, while the problem is not confined to the operationalisation of peacetime ROE in LSCO, it unfortunately extends to the use of force in situations of self-defence. LOAC defines the term “attack” as an “act of violence against the adversary, whether in offence or in defence” (AP I, art. 49(3)). While the term “attack” usually connotes offensive operations, it is less clear how it operates in self-defence contexts. According to NATO doctrine (p. 1-23), any individual has the right to exercise self-defence “in accordance with national laws and policy using the principles of Necessity and Proportionality. It is generally accepted within NATO that self-defence encompasses the use of necessary and proportional force, including deadly force, to defend against an attack or imminent attack.”
This brings me to what I consider to be a substantial flaw in the “Engagement Continuum,” as depicted in NATO’s AJP-3.9 (p. 1-11), which makes a distinction between joint targeting (deliberate and dynamic targeting) and troops in contact (combat engagement and self-defence). While the former are subject to LOAC, the latter would be regulated by national law. Similarly, the Danish Military of Defence’s Military Manual on International Law Relevant to Danish Armed Forces in International Relations provides that:
In connection with acts of self-defence, a requirement of proportionality is also applicable. To be lawful, the military force used to counter an attack is required to be adjusted to the degree, intensity, and duration of the attack by the adversary. In military operations in which force is only authorised in self-defence, it will often be this variant of the requirement of proportionality that applies in the RoE for the operation. This requirement of proportionality must not be confused with the requirement of proportionality set forth in [international humanitarian law], which (see above) concerns the relationship between the value of the military objective and the collateral damage anticipated if the attack is executed (p. 75).
This claim is inconsistent with the law and unsustainable. As Article 49 of AP I makes clear, in times of armed conflict, situations of individual self-defence are still attacks (“violence against the adversary, whether in offence or in defence”) (emphasis added). Therefore, any action taken in self-defence against the enemy must still comply with the rules of distinction, precautions in attack, and proportionality as defined in LOAC. One should be very careful not to confuse LOAC provisions with domestic law or IHRL when engaging targets in situations of armed conflict. As correctly noted by Colonel (ret.) Gary Solis:
In times of armed conflict, whether international or non-international, when a lawful or unlawful combatant takes up arms against an opponent combatant, he becomes a lawful target. To fire on the lawful or unlawful combatant is simply a lawful use of force and an exercise of the combatant’s privilege. Self-defence, as the term is used in domestic law, with its potentially contentious human rights issues, is not an issue.
Professor Garraway similarly warned against the wrongful application of IHRL self-defence in the context of combat operations:
The problem is illustrated by an incident that took place at a checkpoint some nine miles south of Basra on 24 March 2003 during operations to capture that Iraqi city. An Iraqi had approached the checkpoint throwing rocks. The commander of the checkpoint made various attempts to persuade him to desist but failed. The Iraqi was eventually shot dead and the commander was also accidentally killed by his own colleagues. The case led to an investigation into the deaths but charges were not brought against the soldiers concerned. The Attorney General gave his reasons in a statement to the House of Lords on 27 April 2006. These were that “the evidence of the soldiers involved in the shooting was that [the Iraqi] was attacking [the commander] and they acted to defend him.” This is classic human rights law. But the incident was taking place during an international armed conflict. Under the law of armed conflict, the right to use lethal force would depend on whether or not the Iraqi was a legitimate target. If he was a combatant, or a civilian taking an active part in hostilities, he was, as such, a legitimate target and there was no need to justify the soldiers’ actions by reliance on self-defence, or the defence of anyone else (p. 504).
The Belgian reservation to AJP-3.9 (p. V) and France’s Manuel de droit des operations militaires (p. 210) are therefore correct when stating that LOAC also applies in these situations of self-defence.
Concluding Remarks
ROE are intended to regulate the use of force and leaders must formulate and promulgate ROE in light of the relevant national and international standards. In MOOTW, the ROE profile, based on the use of minimum force, must reflect the applicable IHRL standards of strict necessity and proportionality, as defined and interpreted by these instruments.
However, in LSCO, commingling “use of minimum force” and “attack” ROE is legally incorrect, gives rise to confusion, and may ultimately lead to mission failure. In times of armed conflict—particularly LSCOs—the LOAC ROE profile should control, not ROE concerning the “use of minimum force,” even when a belligerent uses force in self-defence against an adversary. While LOAC’s attack ROE do not necessarily justify the drafting and promulgation of a separate annex in the OPLAN, military planners can easily integrate them into existing parts thereof (i.e., the OPLAN or the more elaborate Targeting Annex).
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Colonel Chris De Cock (ret.) is a Law Professor at Ghent University and the Free University Brussels and the former senior military legal advisor of the EU’s military-strategic headquarters in Brussels.
Photo credit: UK Ministry of Defence
