Tensions are running high between the nuclear powers of Russia and NATO amidst the Ukraine-Russia war. The era of strategic arms control seems to have ended, or at least been paused, with Russia’s unilateral suspension of the New Start Treaty.
Russia has stationed nuclear weapons in Belarus and is training Belarusian pilots on how to deploy them. Russian authorities have complained about the United Kingdom’s plans to supply Ukraine with depleted uranium rounds to be used by Challenger 2 tanks donated to Ukraine.
Russian authorities have warned that these rounds would turn Ukraine into a “radioactive landfill.” There have also been rumors for the last year that one side or the other may deploy a dirty bomb that would use conventional explosives to scatter radioactive material throughout Ukraine (See here, here, and here). The expected Ukrainian offensive may see Russia resurrect its “Escalate to De-escalate” Strategy to deploy a tactical nuclear weapon to stop an overwhelming conventional attack. An examination of the permissibility of the use of these weapons under the Law of Armed Conflict is needed.
The monstrous destruction of nuclear weapons is difficult to comprehend. Nukemap provides a simulation of this capability. Only one person in history has approved their use, and this was to destroy two Japanese cities and kill thousands of people to force Japan to surrender in World War II. President Harry S. Truman would have been under tremendous pressure to use the atomic bombs to save American and Japanese lives by avoiding an invasion of Japan. The weapons would later serve as a deterrent against a Soviet invasion of Western Europe where conventional Warsaw Pact forces outnumbered NATO. Tactical nuclear weapons—as if a nuclear weapon could be called tactical—would play an important part in this deterrence.
Tactical nuclear weapons are defined by their range and smaller warheads. They are designed to be deployed on a battlefield where friendly forces are present. They may be deployed as a bomb, missile, torpedo, artillery, or even as “suitcase bombs” set to detonate by command or at a predetermined time. Both NATO and the Warsaw Pact planned to use tactical nuclear weapons in the event of invasion. To date, they have never been used in combat.
The International ICJ of Justice (ICJ) struggled with the issue of whether nuclear weapons are legal. The ICJ is one of the principal organs of the United Nations having been created in 1945. Its fifteen judges work to resolve disputes between states and make rulings on international law. The ICJ may also issue advisory opinions when requested by either the UN General Assembly (UNGA) or UN Security Council. The UNGA requested an advisory opinion from the ICJ with UNGA Resolution 49/75K, asking:
“Is the threat or use of nuclear weapons in any circumstance permitted under international law?”
The ICJ opinion (Legality of the Threat or Use of Nuclear Weapons I.C.J. Reports 1996, p. 226, International ICJ of Justice (ICJ), 8 July 1996, hereinafter Nuclear Weapons) recognized the great destructive power of nuclear weapons and noted that “[It] cannot be contained in either space or time,” and “They have the potential to destroy all civilization and the entire ecosystem of the planet.” (Nuclear Weapons ¶35) 28 States provided written comments to the ICJ, similar to amicus curiae briefs, arguing that nuclear weapons were legal or illegal under international law.
States opposed to nuclear weapons argued that the environmental damage caused by them that could not be contained and could last for generations required their prohibition. The ICJ noted this concern and recognized that the law of armed conflict prohibited such reckless destruction to the environment (See Nuclear Weapons ¶¶30-34). The ICJ recognized that neutral countries not involved in an armed conflict using nuclear weapons would be affected by the radioactive fallout, and the opinion endeavored to balance the competing issues on the general prohibition on the threat or use of force (UN Charter Article 2(4)), a State’s right to self-defense (UN Charter Article 51), and the protection of Neutral States (Nuclear Weapons ¶¶89-93).
The ICJ rejected many States’ arguments for or against nuclear weapons as it searched for the applicable international law in treaty or custom in state practice or opinio juris. States opposed to nuclear weapons argued that the fact they had not been used since 1945 showed they were illegal (Nuclear Weapons ¶65). States in favor of nuclear weapons argued their deterrence value through the strategy of Mutually Assured Destruction (MAD) maintained a general peace during this period making them legal (Nuclear Weapons ¶66). The ICJ did not address the deterrence issue (See Nuclear Weapons ¶67) and rejected various proposals that treaties prohibiting certain weapons (Poisons See Nuclear Weapons ¶¶54-56; Weapons of Mass Destruction See Nuclear Weapons¶57), or that nuclear weapons were not affected by Nuclear Weapons Free Zones Treaties (See Nuclear Weapons ¶¶58-63).
The ICJ ultimately determined that the “rules of international humanitarian law applicable in armed conflict and of the law of neutrality” would govern the threat or use of nuclear weapons (See Nuclear Weapons ¶¶74-85). The ICJ noted the law of armed conflict originated with customary state practice before being codified in various treaties such as the Hague Conventions, Geneva Conventions, and their two Additional Protocols (See Nuclear Weapons ¶75). The ICJ noted two primary principles in humanitarian law: the protection of civilians and civilian objects and the prohibition on unnecessary suffering of combatants (See Nuclear Weapons ¶78). Under the law of armed conflict, weapons must be able to distinguish between civilian and military targets and not cause wanton destruction. The benefits to be gained from an attack must not be disproportionate to the threat to protected civilians and civilian objects.
In theory, nuclear weapons might be used to avoid civilians and only target military objects. Tactical nuclear weapons, due to their localized deployment on a battlefield and smaller destructive capability, could be used against military targets and comply with the principle of proportionality limiting the threat to civilians. Surprisingly, the ICJ specifically did not address tactical nuclear weapons and considered all of the risks regarding nuclear weapons regardless of their size (See Nuclear Weapons ¶43).
When considering the nature of nuclear weapons, one might expect the ICJ to declare their threat or use illegal. They seem indiscriminate in their employment and wanton in their destruction. In the two times these weapons were used, cities were targeted and destroyed, but the ICJ did not comment on this. If military personnel and bases are the only targets, civilians would often be in danger since these military objects are often located near or within cities. Furthermore, the widespread environmental damage and lingering radiation fallout that would spread in the atmosphere would pose a continuing risk to civilians worldwide.
The ICJ decision is surprising in that they recognized that the threat or use of nuclear weapons were generally in violation to the law of armed conflict and humanitarian law, but they reserved a possible carve out exception. In a split 7-7 vote, the ICJ President’s casting vote deciding the issue (ICJ Statute Article 12(4)), the ICJ could not “conclude definitively whether the threat or use of nuclear weapons would be lawful or unlawful in an extreme circumstance of self-defense, in which the very survival of a State would be at stake.” (See Nuclear Weapons ¶105). The ICJ did not fully answer the question put to it leaving the existential threat option for the use of nuclear weapons unresolved. The ICJ did provide a fig leaf in a unanimous vote that there is an obligation in international law to pursue nuclear disarmament. (See Nuclear Weapons ¶105).
The ultimate issue on the threat or use of nuclear weapons was not answered. In a general sense, they are prohibited, but the existential crisis scenario remains uncertain. Ukraine is engaged in an existential struggle with Russia. Unfortunately for Ukraine, it agreed to transfer the nuclear weapons on its territory to Russia when it signed the Lisbon Protocol in 1992. It subsequently joined the Nuclear Non-Proliferation Treaty agreeing not to develop or possess nuclear weapons. This leaves only one side in the Ukraine-Russia conflict with nuclear weapons. The Russians may be reluctant to use tactical nuclear weapons on the conquered territory they have annexed which is not recognized by the international community. If the anticipated Ukrainian offensive is successful, Russia might “escalate to de-escalate” with a tactical nuclear weapon. Because Russia is not yet in an existential crisis, this would likely violate international law.
Lt. Col Brent Stricker, U.S. Marine Corps, serves as a military professor of international law at the Center for Naval Warfare Studies, U.S. Naval War College. The views presented are those of the author and do not necessarily reflect the policy or position of the U.S. Marine Corps, the U.S. Navy, the Naval War College, or the Department of Defense.