The Law of War and You

Not Just for Academics, Eggheads, and JAGs, PT. 1

By MAJ Jonathon Krisko

June 24, 2026 | Field Artillery, 2026 E-Edition

Read Time: < 10 mins

U.S. Army PV2 Anthony Rud, a 13F Joint Fire Support Specialist assigned to 3rd Battalion, 7th Field Artillery Regiment, DIVARTY, 25th Infantry Division, relays artillery fires observation data via radio at Laur, Nueva Ecija, Philippines, on April 16, 2026. Salaknib is an annual exercise designed to enhance interoperability and strengthen relationships between partner nations. (U.S. Army photo by Pfc. Peter Bannister)

This article is part one of a two-part series about how fires officers must master law-of-war decision making. Please make sure to read part two for the full overview.

ATTENTION IN THE TOC! An intel asset has identified the probable location of an enemy command element. The enemy leadership has been vexing coalition forces for over a week, directing a highly effective and bloody urban defense that has claimed the lives of many allied soldiers and countless civilians and caused U.S. forces to expend nearly all available precision-guided munitions (PGM) in the theater. A successful strike here could disintegrate the enemy forces, making them more easily neutralized. However, the news comes with a potential problem: The location is a populated civilian residential area, and all indications suggest the command element will displace within the hour. With the air domain contested, your only feasible option is to use your unit’s artillery to fire conventional munitions.

If you are operating with rules of engagement (ROE) that use the comparatively permissive principles of the law of war as its outer boundary—as proposed by the Secretary of Defense in a bid to reassess U.S. policy and enhance lethality—the decision primarily involves weighing the proportionality of the action.¹ In this case, the determination is whether, based on the available information, the collateral damage is expected to be unreasonable or excessive compared to the concrete and direct military advantage gained by the strike.² While such calls may be morally complex in dense urban environments, commanders and field artillery experts on their staffs have made similar calculations for generations, pairing their professional knowledge and experience with the limited information available on an increasingly complex battlefield.

To ensure the United States Army is postured to fight whatever war we are presented with successfully, fires officers at all echelons must understand the law of war and be able to vigorously apply the Department of Defense’s (DoD’s) interpretation of the same to a wide variety of situations.³ They must also understand and leverage resources, including their judge advocates (JAGs), before the next fight to become as effective as possible.

Fires Officers and the Law of War: Imperative at Every Echelon

From the beginning of our nation, American soldiers have had a can-do attitude, overcoming privations and limitations to accomplish their missions. In that proud tradition, it may be tempting to treat the evolving international views on the law of armed conflict as something that current policymakers, academics and (ugh) lawyers worry about while the meat-eaters focus on combat’s tactical and technical aspects. However, combat-arms officers of all grades must remain attuned to this shifting landscape and, most importantly, the U.S. interpretation and application of the law of war. This is especially true for artillery officers, whose craft is highly technical and has a profoundly impactful role, as they will be required to provide accurate advice about employing various weapon systems in populated areas.

A Faster and More Lethal Battlefield

In the rapid and lethal maelstrom that is large-scale combat operations (LSCOs), a JAG may not always be available for instant analysis. For conventional forces below the brigade level, the likelihood of any legal safety blanket will drop to near zero. Fortunately, for many scenarios that will present themselves on the 21st-century battlefield, there is no compelling reason to have a JAG inserted into the kill chain at all. Therefore, according to LTG (Ret.) Charles Pede, then serving as the Army’s 40th Judge Advocate General, commanders “will need to intuitively know and confidently apply the actual rules of war, unhindered by the lingering hangover of constrained COIN [counterinsurgency] ROE.”⁴ JAGs will always have a critical place in advising commanders on complex situations on and off the battlefield and, perhaps most importantly, training units on the practical application of the law of war. However, since combat-arms officers must apply the laws immediately and practically, they must become familiar with them to identify issues, exceptions and exclusions. Those non-lawyers must be confident in using their judgment in all scenarios concerning the law of war while also knowing when something is novel enough to reach out for guidance when the situation permits. Only when adequately trained, read and tested via exercise will commanders be able to apply the right effect at the right time while keeping on the right side of the law and maintaining the United States’ hard-earned reputation as an upholder of rules-based order.

One thing has not changed, however: the importance of cities to warfare and the challenges of fighting in them. Cities are the “heart and guts” of most nations since they tend to be the centers of leadership, economics and culture.⁵ Because of this, they become key contenders for the enemy’s center of gravity at the strategic or high-operational level as they might be “the source of power or strength that enables a military force to achieve its objective.”⁶ Seizing key urban populations might degrade an enemy’s will, deny them key material support or constrain their freedom of action. The importance of cities is borne out across most operations and battlefields. One need not look farther than the Global War on Terrorism (GWOT) to see how cities like Fallujah, Ramadi, and Mosul were key to controlling the country, even though the vast majority of Iraq is rural. Likewise, Vietnam and the Pacific Theater during WWII, often imagined in popular culture as unrelenting jungle fights, included city fighting that proved critical to the conflicts. Given the post-WWII urban expansion, if we fight again in the Indo-Pacific or continental Europe, we will encounter terrain that is even more urbanized than our past experiences.

Sgt. Justin Ortiz, an observer, coach and trainer assigned to Task Force Mountain Warrior, 5th Armored Brigade, First Army Division West, instructs an Airman during base defense training at McGregor Range, N.M., April 13, 2021. The base defense training teaches service members how to balance base security with political and legal constraints, understand the law of war, and rules of engagement. For 5th AR BDE, preparing our partners to go into harm’s way isn’t merely a cold, mechanical process; rather, it’s a dedication to individuals’ strengths and needs, focused on achieving the mission. (U.S. Army photo by Staff Sgt. John Onuoha, 5th Armored Brigade)

From FO to FSCOORD – A Working Knowledge of the Law is Required

A need for a working understanding of the law of war permeates down to the maneuver company and junior FA-officer level, where their fire support teams (FISTs) are responsible for target planning, fire-support coordination and ultimately bringing rounds on target.⁷ Junior leaders need to understand the threshold and application for positive identification of targets established by the operational orders so that they can initiate fire missions as quickly as possible. When we inevitably face non-uniformed enemies who are not obviously members of a declared hostile force, those same junior leaders must feel comfortable rapidly and independently analyzing hostile-act and hostile-intent criteria while alone, unafraid and wholly disconnected from legal support.

As the rank of the officer increases, so often does the complexity of the tasks required. Fires officers at division and higher levels must provide sound targeting advice across vast amounts of space and time while factoring in constantly changing terrain and civil considerations. In any future major conflict, target engagement authority (TEA) will likely be pushed much lower than it has been over the last 20-plus years, something commanders must become comfortable with and support. Accordingly, unit leaders down to the platoon level must be familiar with and comfortable utilizing products such as an authorities matrix. Far from being just some other niche byproduct of the operations process, such a tool should clearly and concisely lay out what effects are delegated to which level of command, allowing covered commanders to quickly identify what they can do on their own authority and what they need to run up the chain. By internalizing and applying the law of war and decision-making aids to fluid combat scenarios, fires officers can instill confidence in their supported units that they can effectively employ their effects wherever needed while meeting tactical, policy and legal requirements. Equally importantly, they can consistently and violently remind the enemies of the United States that they will die under a hail of high explosives no matter where, when or how they choose to fight.⁸

And it’s not just about the U.S. interpretation. When America marches to war, it typically does so with allies, most of whom have more restrictive national policies regarding weapon systems and their employment. Officers working on multinational staffs must know the U.S. positions on means and methods, both inside and out, and understand partner reservations, capabilities and limitations to build the most lethal fire plan possible. Staff officer expertise in these matters will enable senior commanders to create well-defined rules of engagement that do not unduly limit our capabilities beyond what is required by law or national policy.

Moving beyond the battlefield, being well-versed in the law of war allows all officers, in cooperation with their servicing judge advocate, to educate and train their subordinates to be as lethal as possible in fluid situations. Additionally, today’s lieutenants will become tomorrow’s senior military advisers and policymakers. By maintaining a continuous understanding of this issue, experts in the artillery craft will be able to advocate intelligently at high levels for the lawful and aggressive use of high explosives in all environments, thereby maintaining the firepower advantage the U.S. has long held over its enemies.

Latin, Lethality, and the Law

Pundits love to throw around (and occasionally conflate) two Latin phrases when discussing the “justness” of any given conflict: “jus ad bellum” and “jus in bello.” The former, literally “right to war,” addresses the situations where nations are justified in using armed force.⁹ Accordingly, as a nation with a sacred tradition of civilian control of the government and armed forces, these are top-level determinations far outside the ambit of all but a handful of uniformed servicemembers advising senior political leaders. On the other hand, “jus in bello,” or the “right in war,” are the down-and-dirty rules governing the actual conduct of armed conflicts.¹⁰ This makes servicemembers of various grades and positions essential to regulating and enforcing these rules, as they are best positioned to make tactical and technical calls that both accomplish the mission and comply with the “jus in bello” laws of war, depending on the fluid military situation. It is important to note that “jus ad” bellum and “jus in” bello should be analyzed and applied separately, and doing otherwise unnecessarily muddies the water for the warfighter seeking to make rapid judgment calls about discrete battlefield situations.¹¹ For the average warfighter, “jus in bello” is the primary concern. In contrast, “jus ad bellum” and the high-level actions of state actors are best left for academic discussion or after-hours whiskey and cigar chats.

While the law of war is generally considered prohibitive law, with a host of “shall nots” regarding the conduct of hostilities, it inherently recognizes that the enduring historical purpose of war is “the submission of the enemy as quickly and efficiently as possible” to advance political objectives.¹² Additionally, the law embraces violence as an essential element of war, recognizes suffering as an unavoidable consequence of war itself and acknowledges that information available to commanders and staff is often limited and unreliable.¹³ Therefore, the law of war is not designed and should not be construed to unduly hinder combatants or prevent truly devastating effects, even when such actions may incidentally harm civilians. Instead, it exists to reduce unnecessary suffering and destruction that is not required to defeat the enemy efficiently.

That leads to one of the hairiest questions that will confront commanders and the fires officers advising them: How many civilian casualties and how much damage to civilian objects are permissible while conducting an attack? To determine this, commanders must understand current U.S. policy, as outlined in the ROE and the law of war. The “right answer” has changed and will continue to change depending on the type of conflict and its location. Throughout the GWOT, the ROE was significantly more restrictive than what was allowable within the outer limits established by the laws of war. While political leaders have recently expressed a desire to increase overall lethality and narrow the gap between the ROE and what the law of war permits, these statements build upon years of advocacy from the uniformed services. Most importantly, however, the push from civilian leadership provides the necessary policy to cover for change, since while the advice of senior uniformed officials may influence ROE, it is fundamentally a policy decision of the entire United States, factoring in political, diplomatic and social issues in addition to operational considerations.

Thank you for reading part one of this two-part series. Please follow up with part two for a full overview of combat leaders’ need for legal knowledge of battlefield lethality.

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