Rules of Engagement

Not the Tommy Lee Jones and Samuel Jackson film

The rules of engagement are all the rage right now. Reports of who ordered what strike on which boat continue to fill the papers. The White House Press Secretary said Secretary Hegseth was TEA, target engagement authority. The introduction of the term TEA invites the barracks lawyers to come out and offer their takes. I cannot speak precisely to the events of the strikes in September. What I can do is try to explain why this matters.

Foundational to targeting and conducting military operations are core legal considerations. It sounds weird, but the point of leading with the ethics and laws is that they set a floor of expectations for behavior. These include the basic principles of the law of war, understanding how the law of war affects personnel, objects, and places, and the rules of engagement. First and foremost, targeting must adhere to the law of war and ROE. These apply and are binding. They are not affected by military necessity. What that means is that the mere necessity to conduct a strike does not authorize or justify an act that is prohibited by the law.

As an example, there are classes of buildings that are protected. These are hospitals, schools, and places of worship. Attacking those structures is prohibited by the law of war. However, the fact that a building is protected does not mean that a commander cannot attack that facility if there is a military necessity. If an enemy is firing from a hospital on U.S. forces, a commander can remove the protected status. That is a deliberate decision. It is where commanders use the ROE, the law of war, and TEA to support operations, but also to constrain damage to civilians and infrastructure.

Five Principles of the Law of War

There are five fundamental principles in the decision to use lethal force: 1) military necessity, 2) unnecessary suffering, 3) proportionality, 4) distinction, 5) honor. These five principles form the legal and moral bedrock of the law of war. It is detailed in the DOD’s Law of War Manual.

Military necessity seems straightforward. Is what you are doing necessary to defeat the enemy quickly and efficiently? The Law of War Manual states that objects are valid military objectives when “their nature, location, purpose or use make an effective contribution to military action and whose total or partial destruction, capture or neutralization, in the circumstances ruling at the time, offers a definite military advantage.” The U.S. also exempts two categories of objects, military equipment and bases and objectives containing military objectives, from needing further scrutiny.

Unnecessary suffering, or humanity, forbids causing undue pain, injury, or destruction unnecessary to accomplish a legitimate military purpose. This forbids the use of weapons that are designed to harm but not kill, or that are meant to kill after extreme harm and suffering. The U.S. does its part to adhere to this by not keeping weapons that fail this criterion in its arsenal. There can be further restrictions, such as not using certain types of weapons in cities or against dismounted personnel.

Proportionality means that the potential loss of civilian life or damage to civilian objects is not in excess of the concrete military advantage. This case is made clearest by imagining a unit under fire from a high-rise building. They are being fired at from one window/apartment. It would not be proportionate to level the high-rise. There are several reasons this would fail that criterion, but the clearest is that the U.S. has weapon systems, from guided munitions to direct fire weapons, that are better suited for the direct threat and do not raise the potential of civilian deaths and suffering.

Distinction, or discrimination, means that the military must be able to distinguish between armed forces and the civilian population. It must be able to distinguish between protected sites and unprotected sites. This means that commanders have to distinguish what is a concrete military objective and ensure that their attacks are leveled directly against those objectives.

The last, and not least, of the principles is honor. Honor is based both on a belief in fairness and mutual respect. It is also impressed on members of the military that this extends far beyond personal honor and is tied to the honor of the United States. Ideally, the actions that the U.S. military takes in warfare reflect the society they defend.

Protected Status

I already touched on protected status some, but there are restrictions on targeting personnel and objects. You cannot target civilian populations; you are supposed to protect the sick and wounded and prisoners of war. This speaks most directly to the idea of honor. There are also restrictions on objects: medical units, churches and houses of worship, and monuments and cultural markers are all protected. Again, protected status does not mean that the enemy can just do whatever and they are on home base. Instead, it means that anything that jeopardizes these objects or protected people has to be tied to a clear and concrete military objective that a relevant commander weighs.

ROE

Rules of Engagement (ROE) are directives issued by competent military authorities. They mark the circumstances and limitations under which forces can engage in combat. For this, I will use Operation Inherent Resolve (OIR) as the clearest example.

OIR had standing ROE. These were specified down to ground force commanders and delineated what decisions I could make and what decisions I had to push to my higher commanders. The largest distinction was between status-based targets and action-based targets. A status-based target during OIR was a strike against a known ISIS location or personnel who were not actively engaged in combat against U.S. or coalition partners.

A status-based ROE strike required approval by a TEA at an O6 or O7 level (this is a full colonel or one-star general level) during much of OIR. In practice, this meant a commander would need to direct assets to monitor and build a pattern of life on a target, say a command node, observe movement, monitor and count personnel, and mark men/women/children. These slant calls, along with the pattern of life and collection of any signals intelligence, would be built into a packet. A ground force commander would then brief that packet to the TEA.

This brief would include how the target was going to be attacked, what weapons would be used, and whether there was any authorized reattack should the initial attack fail to destroy the building or people were to run. This process often took days to build, and commanders would have layers of JAGs (military lawyers) review the packets, the ROE, and the collateral damage assessments to ensure the operation was legally covered. More than once, these strikes were denied because they did not rise to a level of military necessity. One commander, when being asked for a strike against a place of worship that was clearly being used as a marshalling location and to store weapons, said, “In the next day our forces will occupy that location, but the reputational damage and messaging issues it would cause for us to strike is not worth the short-term return.” This was the crux of the process. It allowed task force commanders the ability to monitor and keep their forces from running too far ahead, while still remaining aggressive.

The other ROEs routinely used were action-based. These were ROE for the use of force in defense of U.S. and coalition personnel. These were used when U.S., allied, and Kurdish forces were under direct attack. During different times under OIR those also required a TEA above the ground force commander, though after a time that authority was provided to the ground force commander directly, but within limits. They were still not able to attack protected sites or personnel without approval from the TEA.

I do not know what happened in the strike cell in September. I cannot imagine a time where the Secretary of Defense would have been the TEA, but I also cannot imagine a time that these strikes would be made without the full team of JAGs looking at the packets. As Clausewitz said, “Everything in warfare is very simple. But the simplest thing is difficult.”