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Ukraine shocked the world (and the Kremlin especially) when it launched a surprise attack with over a hundred kamikaze drones smuggled into Russia and delivered by unwitting Russian truck drivers to locations near sensitive military bases. If Kyiv’s claims are correct, 34 percent of Russia’s strategic cruise missile carriers were taken out of action.

Imagine if something like this happened to the United States. It’s not so far-fetched. We know, for example, that China possesses adapted civilian shipping containers that can house various missiles. They could enter any port on civilian commercial ships. What if a war with China breaks out by hundreds of these missiles taking out the bulk of the U.S. fleet in American ports on the east and west coasts as well as in Hawaii, all launched from ships operated by COSCO, a Chinese civilian shipping company with known ties to the People’s Liberation Army? What if we were to tell you that their ships already routinely dock within just a few miles from U.S. naval installations? The homeland security threat is real, and the same risks extend to any American military campaign in the Indo-Pacific, where the majority of container ships operate. If the United States is to defend Taiwan or treaty allies like Japan or Korea, the threat of container missiles on board ships poses a new and vexing maritime threat.

If you play the game, you must know the rules. How will the laws of targeting and rules of engagement apply in such a contingency? Unfortunately, U.S. military commanders are poorly trained on these matters, if they are even trained at all.

As the Defense Department shifts toward deterring war or winning a conflict in the Western Pacific, a grasp of the legal concepts required for mission accomplishment has lagged.

The Multi-Domain War

The challenge for the United States and most of its allies and partners lies in the fact that the legal principles applied during land warfare and counter-insurgency operations in Iraq and Afghanistan differ dramatically from those that govern battles in the maritime littorals to defend Taiwan, Japan, or the Philippines.

The differences in how the law of targeting applies on land and at sea are relatively unknown, as the principles of distinction and proportionality are domain-specific. U.S. forces are not well trained in this area. Professional military education provides at most a few hours on the law of armed conflict — hardly enough to understand the basic rules, let alone grasp the subtle but significant distinctions between protections afforded to civilians and civilian objects on the ground versus mariners at sea. Commanders and line officers are responsible for decisions, and American judge advocates have limited exposure to operational law. Most with deployment experience have learned lessons in counterinsurgency and irregular warfare that do not translate well to the multi-domain environment.

The U.S. military’s shift toward multi-domain operations in East Asia requires rapid adaptation to naval warfare’s new realities, especially China’s prospective employment of missile-armed civilian container ships. If war breaks out, commanders and legal advisors will be forced to grapple with complex issues of distinction and proportionality under the law of naval warfare, reshaping operational practices and strategic decision-making in the Indo-Pacific. The U.S. military should extensively train commanders in the specific rules of naval warfare, clearly communicate targeting policies to regional allies and commercial shipping entities, and actively engage in international forums to address this emerging threat.

The U.S. armed forces are shifting focus from war planning in South Asia to East Asia, with profound implications for force structure and theater strategy. These changes also implicate the law of armed conflict and require learning the law of naval warfare. Rather than fighting insurgencies and nation-building, new Indo-Pacific Command Army and Marine Corps campaign strategies call for fighting and winning in the maritime littorals of the first and second island chains. China threatens to dominate this vast area with an enormous force of mobile land-based missiles, as well as a modernizing and growing navy that eclipses the U.S. fleet in size if not capability. Beijing’s mobile land-based systems on the mainland, like the DF-21 and DF-26, are designed to wipe out American air bases and aircraft carriers.

To meet this threat, the U.S. armed forces are reconfiguring to deliver long-range strikes. The U.S. Army,  U.S. Marine Corps, and U.S. Air Force are each testing new operations and basing concepts to bring fire against shipping in the Western Pacific. These forward strategies seek to close the distance to the adversary, but they also place more forces at risk in the weapons engagement zone. Both the United States and China are seeking ways to enhance survivability and complicate enemy targeting in the weapons engagement zone. One of the best strategies is to disaggregate or widely distribute forces across this vast maritime theater to avoid putting all their “eggs in one basket.” China is ahead in this approach, with the world’s largest theater or intermediate-range missile force and now the world’s largest navy. Beijing has an additional asymmetric advance to multiply fires in the weapons engagement zone: civilian merchant ships. China’s armed forces are supplemented by a vast fleet of civilian and commercial ships distributed throughout the region, including fishing vessels, ferries, and container ships, that serve as illicit naval auxiliaries.

The People’s Armed Forces Maritime Militia serve as Beijing’s “fishermen spies.” It has been a decade since the U.S. Naval War College first cast a light on this force and its role in supporting the People’s Liberation Army Navy. More recently, the Naval War College has exposed China’s civilian vehicle ferries, special barges, and cargo ships to support landing force logistics and heavy lift of Chinese troops and armored rolling stock invading Taiwan.

As we mentioned above, China’s greatest advantage with civilian ships, however, may be in hiding theater-range missiles in shipping containers on board container ships. China’s Container-type Sea Defense Combat System presents this new and complex distributed threat. These systems use standard intermodal shipping containers to house powerful weapons, allowing them to blend into civilian maritime traffic and remain concealed until launch. The system was unveiled at the 2022 Zuhai Airshow and requires only a crew of four. It is internally powered, does not need any external support, and reportedly has no electronic emissions. Targeting data is passively downlinked. The system carries up to four missiles, including the YJ-12E supersonic anti-ship cruise missile, YJ-83 medium range subsonic anti-ship cruise missile, YJ-62 long-range subsonic anti-ship cruise missile, PL-16 anti-radiation cruise missile, and the YJ-18E supersonic anti-ship cruise missile.

These “Trojan Horses” could ply international trade routes and enter ports from Long Beach in California to Kaohsiung in Taiwan. Retired U.S. Navy intelligence officer Jim Fanell said, “If this capability is confirmed, it will require a completely new screening regimen for all Chinese-flagged commercial ships bound for U.S. ports.” Employing civilian ships in these ways distributes lethality throughout the region, making them harder to locate and target, and creates legal and political dilemmas for the United States. It is not certain container missile systems will be deployed, but Rick Fisher, a senior fellow at the International Assessment and Strategy Center said doing so “fits with China’s penchant for seeking asymmetric advantages against its enemies.” China has a tendency to prefer “deniable weapons systems that are difficult to identify or track,” Fisher said.

Civilians and Civilian Objects in Armed Conflict

Using civilian ships to attack the enemy and targeting the enemy’s container missile carriers raises confounding legal problems. There are only two ways to deploy missiles on civilian ships, which are protected civilian objects during armed conflict and immune from attack. First, the flag state could convert container ships to warships. A flag state may convert any merchant ship into a warship, satisfying legal requirements that allow it to be treated as a combatant platform, acquiring sovereign immunity and belligerent rights, but also exposing it to attack. Second, states may surreptitiously place missiles on container ships. This action constitutes perfidy because it unlawfully invites the confidence of the enemy by exploiting the protected status of merchant ships under international law. Article 37 of Additional Protocol I to the Geneva Conventions defines perfidy as “[a]cts inviting the confidence of an adversary to lead him to believe that he is entitled to, or is obliged to accord, protection under the rules of international law applicable in armed conflict, with intent to betray that confidence.”

Whether China’s new missile-armed container ships are done lawfully through conversion to warships or unlawfully through perfidy, Indo-Pacific Command planners are stuck with the legal dilemma of whether or when container ships carrying missiles may be attacked.

The Principle of Distinction

If some portion of China’s container ships are converted to warships, they qualify as military objects and may be targeted at any time during hostilities. If China deploys missiles on container ships, the act would constitute perfidy. Perfidy violates the legal principle of distinction: the obligation of parties to a conflict to distinguish between combatants and military objects, such as warships, from civilians and civilian objects, like container ships. The “cardinal” and “intransgressible” principle of distinction in targeting law is set forth in paragraphs 78 and 79 of an International Court of Justice advisory opinion on nuclear weapons. It requires combatants to distinguish at all times between civilians and civilian objects and combatants. The International Court of Justice determined “[s]tates must never make civilians the object of attack and must consequently never use weapons that are incapable of distinguishing between civilian and military [objects].”

However, if a container ship is operated as a weapons platform, even if it contains just one cruise missile that endangers the enemy, the entire ship becomes a legitimate military target. Section 8.6.2.2 of the 2022 U.S. Commander’s Handbook on the Law of Naval Operations, for example, states enemy civilian ships may be attacked and destroyed, either with or without warning, if they are armed with weapons systems capable of harming the enemy and there is reason to believe that such armament has been used, or is intended for use, in offensive operations. This excludes light armament for anti-terrorism or force protection. The Commander’s Handbook lists other criteria that expose civil or merchant shipping to attack, including a persistent refusal to stop upon being duly summoned, actively resisting visit and search or prize capture, and sailing under convoy of enemy warships or enemy military aircraft. Section 8.8 of the Commander’s Handbook concludes civilian ships may be attacked if they are being incorporated into, or assisting in any way, the intelligence system of an enemy’s armed forces or acting in any capacity as a naval military auxiliary to an enemy’s armed forces. In short, enemy merchant ships are normally civilian objects and may not be attacked, but they lose their special protection if they are integrated into the enemy’s warfighting or war-sustaining effort. When this occurs, the merchant ship is “taking a direct part” in hostilities. When a commander makes this finding, it not only satisfies the principle of distinction, but it also raises another issue with the principle of proportionality.

The Principle of Proportionality

Section 15.4 of the Department of Defense Law of War Manual restates the customary rule that civilians on land generally cannot be targeted except for such time they are “directly participating in hostilities.”  By comparison, section 7.5.1 of the Commander’s Handbook on the Law of Naval Operations states civilian ships may not be targeted unless they are taking a “direct part in hostilities.” The terms used on land and at sea are almost identical, but they are not the same and the subtle difference reveals profound implications for targeting in the principle of proportionality.

If a container ship loses its protected status and becomes a lawful target, commanders are obligated ensure their attacks against it are proportional. Proportionality is a core principle of the law of war, as set forth in section 5.5 of the second edition of the Newport Manual on the Law of Naval Warfare. It prohibits attacks that are expected to cause harm to civilians or civilian objects that would be excessive in relation to the anticipated concrete and direct military advantage.

In land warfare, the law of armed conflict emphasizes the protection of individual civilians, and commanders weigh expected proportionality in terms of civilian lives lost and civilian objects injured or destroyed. Ground combat often occurs in or near population centers, where non-combatants can easily intermix with legitimate military targets. In Afghanistan, Iraq, and the conflict in Gaza today, distinguishing combatants from civilians is a persistent challenge. As a result, contemporary scholarship and doctrine under the law of armed conflict often focuses on minimizing harm to individual civilians. The goal of civilian harm mitigation became controversial in Iraq and Afghanistan but this issue is dramatically less salient during the law of naval warfare, even against civilian container ships carrying missiles.

In naval warfare, ships, submarines, and aircraft of the enemy — not individuals on board — are lawful targets. Importantly, if a warship (or a container ship with missiles) is a lawful target, the composition of its crew, even if partially or completely civilian mariners, does not factor into the proportionality analysis. Only civilians present nearby but off the ship, such as those on a civilian vessel alongside the target ship, are included in the proportionality analysis. On this point, Lassa Oppenheim, perhaps the greatest international lawyer of the past 150 years, wrote in section 202 of his landmark Treatise that non-combatants on warships suffer the same fate as the vessel itself:

Just as military forces consist of combatants against non-combatants, so do the naval forces of belligerents. Non-combatants, as for instance, stokers, or naval surgeons, chaplains, members of the hospital staff, and the like, who do not take part in the fighting, may not be attacked directly and killed or wounded. But they are exposed to all injuries indirectly resulting from attacks on, or by, their vessels; and they may certainly be made prisoners of war, unless they are members of the religious, medical, and hospital staff, who are inviolable…

This platform-centric focus significantly shapes targeting decisions at sea. The painstaking collateral damage estimation and proportionality analysis many warfighters and judge advocates applied in Southwest Asia are not required when targeting warships or civilian ships integrated into the enemy force. Individuals on board warships, regardless of their civilian status are still exposed to injury or death if the ship itself is being used in the service of the enemy.

The Newport Manual on the Law of Naval Warfare (Second Edition 2025) reflects this approach in  section 8.8.1. Likewise, the International Committee of the Red Cross, which is steadfast in minimizing the effects of war on civilian populations, incorporates this interpretation in its Commentary of Additional Protocol I. Paragraph 1903 of the Commentary states that “[a]t sea, civilians on board warships run the risks to which such ships are exposed. If they are on board enemy merchant ships, their fate will depend on the nature of these vessels.”

Operational Considerations

Maritime deception is not new, but the advent of advanced, mobile weapon systems housed in civilian-looking containers raises the stakes considerably. Given the complexity of shifting flag states, opaque ownership structures, and multinational crews, assessing whether a container ship can be targeted is based on its behavior and capability — not presumed intent or identity. For instance, a vessel could be flagged in Panama, owned by a Chinese company, and crewed by mariners from India, the Philippines, and Ukraine with a Korean master. Further complicating matters is the possibility or even likelihood that the ship’s crew is unaware they are a mobile platform for a containerized missile system. Commanders will be confronted with vessels that appear to be civilian ships as their registration, nationality, and electronic emissions, such as the automatic identification system, suggest they are protected civilian objects; however, in fact, they pose an immediate threat.

Conclusion

Engaging enemy or neutral civilian ships — especially with neutral multinational crews — carries political and potentially strategic risks. If a mistaken strike occurs or if the adversary succeeds in portraying an otherwise lawful attack as illegitimate, the consequences will include diplomatic backlash, erosion of international support, or damage to the perceived legitimacy of U.S. operations. Worse, adversaries may provoke such a response deliberately to generate strategic propaganda or deter future engagements. But the legal doctrine is clear: merchant ships in the service of the enemy are lawful targets, and the proportionality analysis factors in only the expected civilians or civilian objects in the vicinity of the ship that could be injured or destroyed, and not those crew members or passengers on the ship itself. The entire ship becomes a lawful target, and the people on board, whether willing or unwitting, stand in peril because of the misuse of the vessel.

How can commanders, their staffs, and judge advocates adapt to the new rules of war in the Indo-Pacific? First, just because a strike against a civilian merchant ship is lawful does not necessarily mean a commander has to do it. There may be other tactical means of neutralizing the threat, such as persuading neutral state port authorities to prevent suspicious Chinese-owned or -affiliated container ships from getting underway, thereby keeping them out of the theater of conflict. Second, commanders may exercise the belligerent right to visit and search enemy and neutral merchant ships. All enemy ships may be seized and converted as prize. Neutral ships may also be seized if they are carrying contraband or are integrated into the enemy force.

These tactical responses require training across joint and combined forces to address the new threat and its associated legal implications.

The Department of Defense requires law of war training, but it has not kept pace with the times. Neither the extent of current training nor the topics covered adequately prepare forces deployed in Indo-Pacific Command for the new rules of war. Commanders and their staffs should be retrained not only in the law of war but the overlapping and distinct laws of naval warfare. Old principles in the law of war, like distinction and proportionality, play out differently at sea and virtually no one in the U.S. armed forces is savvy. Every officer deployed to an operational billet in Indo-Pacific Command should understand the Commander’s Handbook on the Law of Naval Operations (2022) and the Newport Manual of the Law of Naval Warfare (Second Edition 2025). Every judge advocate in the region should have the major contours of the rules committed to memory. These resources will help inform decision-makers who will be required to exercise high-risk judgment under conditions of great uncertainty. Line officers and public affairs officers should be able to explain these rules to allied governments and media.

Making decisions about container missile threats requires better maritime domain awareness. Investment in intelligence, surveillance, and reconnaissance assets is critical, but so is an understanding of civilian ship registrations, shipboard and port facility security protocols, and cargo chain of custody certificates. AI can more quickly analyze civil shipping data, such as distributed ledgers for shipping certificates, satellite monitoring of cargo flows, anomaly detection in identification signals, and automated data fusion systems that track changes in vessel behavior or ownership.

Finally, there needs to be frank conversations with China, regional allies, and strategic partners about the risks to civilian shipping so that they will play constructive roles in preventing or identifying perfidy, and accepting the legitimacy of Indo-Pacific Command strikes against these ships if they are misused. In 2020, Chief of Naval Operations John Richards, for example, stated that China’s maritime militia fishing vessels may be attacked if they support the People’s Liberation Army Navy during an armed conflict. Similarly, senior leaders must first understand the rules and then engage regionally and globally, so that flag states, ship owners, and operators understand that their vessels can become military objects and could be destroyed in the event they are engaged in perfidy during a naval war. Seafarers should also understand the risks so that both labor and management have a vested interest in exercising due diligence to prevent their ships from being misused. Bilateral and multilateral engagements in Indo-Pacific Command can serve as forums to calibrate expectations regarding the lawful use of civilian merchant ships and the consequences of perfidy. In addition to regional engagement, the United States and its allies should raise these issues at the International Maritime Organization, the UN agency for shipping regulation, and the International Labor Organization, the UN agency with oversight over seafarer safety and welfare.

Just as NATO states are drawn to negotiating new agreements to address security threats, Association of Southeast Asian Nations states are also seeking consensus. However, it is unlikely that a regional instrument will emerge that provides greater clarity and guidance, such as requiring certain classes of cargo ships to be declared in conflict zones, promoting international inspections at sea, or even negotiating new norms around the deployment of containerized weapons. An agreement cannot be completed and if one is adopted, China will not comply. For example, even the members of the Association of Southeast Asian Nations now acknowledge that the 20-year effort to negotiate a code of conduct with China has stalled. Despite a looming 2026 deadline, no state is confident of reaching an agreement. The purpose of the code of conduct? To provide greater fidelity on compliance with the rules of the U.N. Convention on the Law of the Sea. In 2016, an international tribunal composed under the Law of the Sea unanimously determined China was a serial violator of the treaty.

James Kraska is Charles H. Stockton professor of international law and chair of the Stockton Center for International Law at the U.S. Naval War College and John Harvey Gregory lecturer on world organization at Harvard Law School. He is a graduate of Mississippi State University, Indiana University Maurer School of Law, and the University of Virginia School of Law. He is a former Navy judge advocate who served as the legal adviser for Expeditionary Strike Group SEVEN/Task Force 76 and as the director of international negotiations on the Joint Staff.

Gavin Logan is deputy chair of the Stockton Center for International Law and an officer in the U.S. Marine Corps. He is a graduate of Auburn University, Cumberland School of Law, and The Judge Advocate General’s Legal Center and School of the Army. He has served as command legal advisor for Task Force 51/5, 3d Marine Aircraft Wing, and Marine Corps Recruit Depot San Diego, as well as a U.N. peacekeeper and company commander.

Image: Midjourney