Rescue at Sea in Armed Conflict – A Legal Analysis of the Obligations Applicable Following the Use of Armed USVs

[Dr Sally Longworth is a researcher and Julia Dalman is an analyst at the Swedish Defence Research Agency]

On 2 May 2025, a Ukrainian unmanned surface vehicle (USV) successfully engaged a Russian fighter jet close to a Russian naval base in the eastern Black Sea. The attack was likely carried out by a Magura-V7. The two-person crew of the fighter jet ended up in the Black Sea where they were later rescued by a civilian ship. The attack marks the first successful strike by a USV against an enemy fighter jet. Another Russian fighter jet was reportedly hit in the early hours the day after. This development followed what is claimed to be the first sea to air strike ever made by a USV in December 2024, when a Magura-V5 shot down two Russian Mi-8 helicopters. The video released by Ukrainian military intelligence afterwards included sound recording from the pilot saying “I’m hit, I’m going down!”. Ukraine has developed USVs remarkably quickly and used them to great effect against Russia’s larger and more powerful naval forces to deny Russia sea control. One of the most notable examples is the use of a “swarm” of Sea Baby USV’s attacked and destroyed parts of the Crimean Bridge in August 2023. 

Scholarly debates on the use of USVs in Russo-Ukrainian naval warfare have given great attention to how these USVs should be classified under international law of the sea (see, for example, here, here and here), be that a ship, a warship, a vessel, equipment, or something else. These designations have legal and practical implications, not least in relation to belligerent rights and navigations rights. Less attention has been given to how this transformation in naval operations impacts the implementation of essential protection obligations under international humanitarian law (IHL). As a result of these various attacks, combatants are left shipwrecked and injured at sea. How USVs are classified under IHL has consequences on what obligations are applicable to the parties to the conflict in relation to those shipwrecked or injured at sea resulting from an attack. This post outlines these issues in light of the recent developments in attacks by armed USVs in the Russo-Ukrainian armed conflict at sea. 

Classifying USVs

Numerous ways to describe USVs have been put forward (see here and here, for example). They are broadly categorised as a craft designed to travel in water on the surface by means of controlled (i.e. not random) movement without any personnel on board. USVs are used for several purposes, such as intelligence, surveillance and reconnaissance; electronic warfare; attacks; and search and rescue operations. As such, they are not necessarily armed. Given the breadth of functions USVs serve in naval operations, it is therefore unlikely that there will be one legal definition that fits all USVs.

How USVs are classified under the law of the sea impacts on where, when and how they are used in armed conflicts. Only warships have belligerent rights in naval warfare, according to which only warships can use armed force. Warships are defined in Article 29 UNCLOS as: 

a ship belonging to the armed forces of a State bearing the external marks distinguishing such ships of its nationality, under the command of an officer duly commissioned by the government of the State and whose name appears in the appropriate service list or its equivalent, and manned by a crew which is under regular armed forces discipline.

The definition is the same under IHL (see, for example, 1907 Hague Convention VII (article 2-6) and San Remo Manual (Rule 13(g)).

There is a growing acceptance a USV could be crewed remotely and commanded by an officer who is not on board the USV. The IMO Guidelines on Maritime Autonomous Surface Ships (MASS) Trials also anticipates the possibility of remote operators.

To date, Ukraine has not registered either the Magura or the Sea Baby as a ship or a warship, however, but has used them to carry out acts in attack. Both are considerably smaller than relatively small warships in use today, such as patrol craft. Whereas the Sea Baby has generally been used to carry out attacks by colliding into targets, the Magura has been used to launch explosive weapons against targets in attacks. 

From an IHL perspective, these USVs clearly constitute means of warfare. Means of warfare are objects used for the purposes of delivering force in hostilities, such as weapons, weapon launchers or weapon platforms. IHL applies to the use of all weapons in connection with the armed conflict, but there is no definition of the broader concept of “weapon” under any IHL treaty. Restrictions and prohibitions are instead placed on defined specific weapons. 

As a weapon of naval warfare, it is without question that the legal framework governing the conduct of hostilities apply to the use of USVs. It also follows that protection obligations that arise following the use of such weapons also apply. How these obligations apply, however, deserves further consideration.

The Application of the Duty to Render Assistance under the Law of the Sea 

The duty to render assistance at sea and rescue persons in distress is set out under Article 98 UNCLOS and is firmly established in customary international law. The obligation to render assistance continues to apply in armed conflict, and is also applicable to warships and other military vessels. 

Article 98 sets out requirements that flag States must ensure the masters of the ship carry out. As noted above, USVs do not have a master on board, but there is general acceptance that a commander could be appointed to act in such a capacity remotely. This, however, would not overcome the problem that the USVs currently in use are not able to transport people.

Under Article 98 UNCLOS, the obligation to render assistance applies only so far as the master “can do so without serious danger to the ship, the crew or the passengers”. The need to safeguard the rescuing vessel is a recognised exception to the rule that would apply equally to USVs as it would to manned vessels. It has also been argued that after a warship has conducted an attack, the danger of it being targeted or sunk may also entail that the obligation to render assistance is not applicable. In relation to USVs, this exception would seem relevant where it is not possible for the USVs to rescue persons in distress or in danger of being lost at sea. The term “render assistance” is broader, however, than “rescue” and it could be that the sensors and other technology on board the USV enable other ships in the area and/or coastguards and rescue centres to rescue persons in distress.

These ambiguities make the obligation under Article 18(1) GCII to search and collect for casualties after each engagement of attack even more important. They also highlight the complimentary nature of IHL in this area. 

The Obligation to Search for and Collect Shipwrecked and Wounded Persons under IHL

Under Article 18(1) GCII, after each engagement the parties to the armed conflict must without delay take all possible measures to search for and collect the shipwrecked, wounded and sick, to protect them against pillage and ill-treatment, to ensure their adequate care, and to search for the dead and prevent their being despoiled. Reviewing and updating the implementation of Article 18(1) GCII where armed USVs are used is therefore an imperative. 

In naval warfare, the obligation to search, collect and evacuate wounded, sick and shipwrecked persons only arises after each engagement. It is addressed first to commanders on the spot or nearby, but broadly addressed to the “parties to the conflict”. As such, the fact that no commander is physically present on the USV does not result in this obligation not applying, but rather requires parties to the conflict to take other measures to fulfil the obligations. 

The duty must be undertaken “without undue delay”, but is an obligation of means. The capabilities of the parties and the practicalities of the situation at hand will therefore determine the scope of the obligation. As such, the commander of the attacking vessel may not be obliged to rescue wounded and shipwrecked persons from the enemy’s vessels following an engagement where other vessels in the immediate vicinity are capable of doing so (see ICRC Commentary to GCII 2017, paras. 1649-1650). 

At the very least, the attacking party must not hinder search and collection efforts, or otherwise arbitrarily impede rescue actions. Armed USVs still in the area following an attack must therefore be able to distinguish between military vessels used for the purpose of rescuing others (e.g. temporary medical transport), hospital ships and any other humanitarian or civilian vessel rescuing wounded or shipwrecked persons after an engagement (see San Remo Manual, Rule 47). In addition, they must be able to navigate and operate so as not to interfere, hinder or impede the rescue efforts. 

In planning of attacks with armed USVs, the attacking party would anticipate the potential for shipwrecked, wounded and dead persons as part of the legal assessment of the effective contribution of the military objective targeted and direct military advantage gained in the attack. The attacking party would thereby be on notice to ensure sufficient preparations are made so as to be enable their rescue and ensure the care and protection required under IHL is provided. Failing to do so raises at the least a violation of the obligation to ensure respect for IHL, if not a violation of Article 18 and the obligation to respect IHL. 

The obligation to search for and collect the wounded and shipwrecked is applicable to all conflict parties. As such, the defending party may also need to dedicate further resources to the obligations to search, evacuate and collect the wounded, shipwrecked and dead in the knowledge that this will not be possible to undertake by the enemy following engagements involving armed USVs. Under Article 18(2) GCII, the parties to the conflict are obliged to conclude local arrangements for the passage of medical and religious personnel and equipment on their way to besieged or encircled areas whenever circumstances permit. This obligation could similarly be extended to areas where armed USVs are used in attack so as to ensure that the protection obligations for shipwrecked and wounded persons at sea are maintained.

Conclusion

The use of armed USVs by Ukraine has been acclaimed as an innovation in naval warfare, but in many ways the legal questions that arise are not new. The development of torpedoes, over-the-horizon missiles and similar technology has raised similar questions about how to implement these protection obligations. But as seen with technological developments of the past, each new iteration raises its own unique issues. The total absence of a crew on board USVs fundamentally changes the way the obligations to search for, collect, protect and provide care for shipwrecked and wounded persons at sea are implemented. However, it does not change that the obligations still apply. These technological advances could themselves be part of the answer, as USVs and other unmanned vehicles could be used to assist in the search for shipwrecked persons. This again demonstrates that there is never likely to be a one size fits all definition of USVs, and determinations will need to be made on a case-by-case basis. The capabilities and functions of the USV will impact how it is classified under both the law of the sea and IHL. If USVs are ever used to transport the shipwrecked or wounded, they may fall within the definition of a temporary medical transport, for example. If an unarmed USV is used for military intelligence rather than in attack, it would still fall within the definition of a military objective. And as noted, if the USV is armed, it will classify as a means of warfare under IHL. In the meantime, parties to the armed conflict must plan for and take sufficient measures to ensure that their obligations relating to shipwrecked, the wounded, and dead are upheld in circumstances where armed USVs are used.