Interdiction fire in urban areas: status under international law?

Question

Somewhat related to my other recent question... there's footage of (almost certainly Russian) mortar interdiction fire landing on an empty intersection in Kharkiv (last week).

The US army too used to have this kind of tactic, but it was largely abandoned during/after Vietnam.

HARASSMENT and Interdiction (H&I) fire, a type of artillery mission practiced by the United States Army throughout two world wars and bitter fighting in Korea, proved controversial during the Vietnam War. Before America’s large-scale ground commitment in 1965, the army had drawn H&I into new, but rudimentary, tactical doctrine for prosecuting counterinsurgency warfare. As in previous conflicts, H&I constituted those artillery missions, not visually directed by friendly personnel, that targeted Viet Cong (VC) or North Vietnamese Army (NVA) routes and positions. These unobserved missions consisted of no more than a few rounds fired at random intervals throughout the night, and sometimes during the day. Usually based on rough tactical intelligence, these strikes did not aim directly at enemy soldiers. Instead, they sought to achieve a larger purpose: to inspire in the enemy a fear of random casualties. This fear, H&I proponents contended, would curtail the enemy’s freedom of movement and also hurt his morale. In a war without fronts, however, profligate employment of such unobserved strikes offered few benefits and harbored a significant potential to harm Vietnamese civilians or their property. Some officers identified this problem early in the war and argued against the practice, but the army nevertheless fired the majority of its artillery strikes, and nearly half of its artillery ammunition, as H&I during 1966 and 1967. The army reversed course, nearly eliminating H&I by mid-1970, and antiwar activists such as John F. Kerry deemed H&I a “war crime” allegedly perpetrated as “accepted policy by many units in South Vietnam.”

So, given the increased level of controversy with the practice in more recent times, I'm curious if there were such practices invoked or analyzed for conflicts that "went to court" like that in former Yugoslavia (ICTY).

Basically, can one still fire interdiction missions in urban areas nowadays, under modern interpretations of international law?

Answer 1

Broadly, and not from the point of view of any legal authority:

The rules of war, or international humanitarian law (as it is known formally) are a set of international rules that set out what can and cannot be done during an armed conflict.

https://eu.usatoday.com/story/news/world/2022/03/01/war-crimes-possible-punishment-if-found-guilty/6971469001/

https://thewire.in/world/what-constitutes-a-war-crime

https://ihl-databases.icrc.org/customary-ihl/eng/docindex/v1_rul_rule156

https://www.icrc.org/en/doc/war-and-law/treaties-customary-law/geneva-conventions/overview-geneva-conventions.htm

The use of H&I fire is mentioned here:

https://casebook.icrc.org/case-study/icrc-international-humanitarian-law-and-challenges-contemporary-armed-conflict-2019

At times, explosive weapons with a wide impact area (most commonly artillery or other indirect fire weapon systems) are used to harass the enemy, to deny them freedom of movement, or to obstruct their activities (“harassing”, “interdiction” or “suppressive” fire). This takes the form of a continuous flow of fire – often of low or moderate intensity – intended to deliver effects over an area or on specific objects or persons, depending on the circumstances. However, to be lawful, harassing, interdiction or suppressive fire must be directed at a specific military objective, and must use means capable of being so directed. Yet in practice it is not always clear that this is the case.

However, there is overlap - if the location, that just so happens to be in a civilian urban area is regarded as a military objective (perhaps locals have pointed out combatants operating in the area), then it could be seen as lawful. You could be covered if you had an observer in the area or a drone observing for example.

The Department of Defense Law of War Manual shows possible options:

DoD Law of War Manual - June 2015 Updated Dec 2016.pdf

5.4.6 Force That May Be Applied Against Military Objectives

In the absence of expected harm to civilians and civilian objects or of wanton destruction that is not justified by military necessity, the law of war imposes no limit on the degree of force that may be directed against enemy military objectives, including enemy military personnel

For example, the principle of military necessity does not require that only the minimum force that is actually necessary in a specific situation may be used against military objectives. Instead, the broader imperatives of winning the war may be considered, and overwhelming force may be used against enemy military objectives.

In particular, the following practices are not prohibited: (1) surprise attacks; (2) attacks on retreating forces; (3) harassing fires; and (4) attacks on specific individuals.

5.4.6.3 Harassing Fires.

Harassing fires against enemy combatants are not prohibited. (Such action is clearly distinguishable from attacks to terrorize or otherwise harm the civilian population, which are, of course, prohibited.) Harassing fires are delivered on enemy locations for the purpose of disturbing enemy forces’ rest, curtailing their movement, or lowering their morale.

APPENDIX TO 1985 CJCS MEMO ON AP I 47 (“Harassing fires are delivered on enemy locations for the purpose of disturbing the rest, curtailing the movement, or lowering the morale of troops.”).

5.6.6 By Its Nature, Location, Purpose, or Use Makes an Effective Contribution to Military Action.

The first part of the test is whether the object, by its nature, location, purpose, or use makes an effective contribution to the enemy’s military action.

The location of an object may provide an effective contribution to military action. For example, during military operations in urban areas, a house or other structure that would ordinarily be a civilian object may be located such that it provides cover to enemy forces or would provide a vantage point from which attacks could be launched or directed. The word “location” also helps clarify that an area of land can be militarily important and therefore a military objective.

Areas of land that have been regarded as military objectives have included, for example:

1. road networks;
2. known or suspected enemy avenues of approach or withdrawal;
3. mountain passes, hills, defiles, and bridgeheads; and
4. villages, towns, or cities whose seizure is militarily important.