General Discussion

The Prohibition of Ordering Denial of Quarter or Denying Quarter
Assuming solely for the sake of discussion that there was a non-international armed conflict at the time of the Sept. 2 strikes, the most relevant LOAC rule applicable to the Hegseth and Bradley orders is the “denial of quarter,” i.e., an instruction not to allow any survivors (see, e.g., Working Group of Former Judge Advocates Generals’ statement on the Hegseth order).

The status of the prohibition on the denial of quarter (and on ordering or threatening its denial) was settled well over a century ago. It is applicable in both international and non-international armed conflicts as a matter of customary international law (ICRC, Customary International Humanitarian Law study, Rule 46). This is so with respect to its status as a violation of LOAC entailing the responsibility of the State concerned and as a war crime by the individuals issuing orders to deny quarter or carrying them out. We need not repeat here the major international texts and tribunal decisions that support that conclusion. One of us (Schmitt) walked through all of the relevant texts, from the U.S. Civil War’s Lieber Code to the present, in a 2023 essay concerning a “kill everyone” order by the head of Russia’s Wagner Group (co-authored with LtCol John Tramazzo).

Here, suffice it to note that the DoD Law of War Manual is categorical: “It is … prohibited to conduct hostilities on the basis that there shall be no survivors, or to threaten the adversary with the denial of quarter. This rule is based on both humanitarian and military considerations.” The Manual further emphasizes that the rule “also applies during non-international armed conflict” (§ 5.4.7).

A closely related prohibition implicated in the Sept. 2 strikes, which also applies in both international and non-international armed conflict, is on attacking those who are hors de combat, a condition that includes those who are “defenseless” because they are shipwrecked (see ICRC Customary International Humanitarian Law study, rule 47 and related practice). As the DoD Law of War Manual explains (§ 5.9.4),

Shipwrecked combatants include those who have been shipwrecked from any cause…. Persons who have been incapacitated by … shipwreck are in a helpless state, and it would be dishonorable and inhumane to make them the object of attack. In order to receive protection as hors de combat, the person must be wholly disabled from fighting.

The Commander’s Handbook on the Law of Naval Operations similarly provides, “Intentional attack on a combatant who is known to be hors de combat constitutes a grave breach of the law of armed conflict” (§ 8.2.3). Indeed, as noted in the Newport Manual on the Law of Naval Warfare published by the U.S. Naval War College’s Stockton Center, Geneva Convention II

sets forth a legal framework for the humane treatment and protection of victims of armed conflict at sea. The Convention requires parties to the conflict to, inter alia, respect and protect individuals falling within the scope of the Convention “who are at sea and who are wounded, sick or shipwrecked.” Parties to a conflict are thus required, after each engagement and without delay, to “take all possible measures to search for and collect the shipwrecked, wounded and sick,” without discriminating between their own and enemy personnel.

To be clear, there is no exception to the prohibition on attacking those who are hors de combat due to being shipwrecked because they might escape or otherwise receive rescue assistance from their forces. The only basis for treating them as subject to continued attack is if they are, in fact, not hors de combat because they continue to fight.

Doctrine and Prosecutions on Denial of Quarter
This analysis of the LOAC rules merits being supplemented with three additional points. First, each U.S. servicemember has an obligation to report evidence that any U.S. operation potentially involved killing shipwrecked survivors or a denial of quarter. According to the Commander’s Handbook on the Law of Naval Operations (§ 6.3; see also DoD Directive 2311.01):

All military and U.S. civilian employees, contractor personnel, and subcontractors assigned to or accompanying a DOD component must report through their chain of command all reportable incidents, including those involving allegations of non-DOD personnel having violated the law of war.

Examples of incidents that “must be reported” include: (1) “Offenses against the Wounded, the Sick, [and] Survivors of Sunken Ships,” such as “willfully killing”; (2) “Other Offenses against Survivors of Sunken Ships,” including, “when military interests permit, failure to search out, collect, make provision for the safety of, or to care for survivors;” and (3) “Denial of quarter, unless bad faith is reasonably suspected” (§ 6.3).

Second, a landmark 1921 case emerging out of World War I clearly set forth the rule that killing shipwrecked survivors of a boat strike is a war crime and that superior orders offer no defense to such conduct, because such orders must be disobeyed. In the Llandovery Castle case, the Imperial Court of Justice considered a June 1918 incident after a German U-boat sank the Llandovery Castle, a Canadian hospital ship. The U-boat Commander claimed he thought the ship was carrying American airmen. In convicting the defendants for firing on the survivors who were in lifeboats, the court noted that by that point, the international legal prohibition on killing survivors of a maritime attack was manifest.

The firing on the boats was an offence against the law of nations. In war on land the killing of unarmed enemies is not allowed (compare the Hague regulations as to war on land, para. 23(c)), similarly in war at sea, the killing of shipwrecked people, who have taken refuge in life-boats, is forbidden.
…

The fact that his deed is a violation of international law must be well-known to the doer, apart from acts of carelessness, in which careless ignorance is a sufficient excuse. In examining the question of the existence of this knowledge, the ambiguity of many of the rules of international law, as well as the actual circumstances of the case, must be borne in mind, because in war time decisions of great importance have frequently to be made on very insufficient material. This consideration, however, cannot be applied to the case at present before the court. The rule of international law, which is here involved, is simple and is universally known. No possible doubt can exist with regard to the question of its applicability. (emphasis added)