On April 10 a Russian-launched cluster bomb exploded on a residential street in the Pysochin suburb of Kharkiv. Viktor Andriiovych, a sixty-six-year-old retired firefighter, quickly whisked his older sister, Oleksandra Andriivna, into the cellar of the home that they shared. Though he saved her, shrapnel from the blasts struck Viktor in the leg. He collapsed and quickly bled to death. “I feel guilty,” Oleksandra later said, “because he came out of the house to save me and was killed. He was a firefighter at Chernobyl when the disaster happened and then he raised his youngest son on his own. He always helped other people, and he died to save me.”

Five days later Oksana Litvynyenko was walking in a Kharkiv playground with her husband, Ivan, and four-year-old daughter. Several cluster munitions exploded around them, gravely wounding Oksana. Ivan described the scene: “When my daughter saw her mum on the ground in a pool of blood, she said to me, ‘let’s go home; mum is dead and the people are dead.’ She was in shock and so was I.”

Russia’s unprovoked violation of Ukrainian sovereignty is a clear-cut case of the crime of aggression.

Such are the stories documented by Amnesty International in its recent report on Kharkiv. The pattern is clear: Russian forces have made frequent use of cluster munitions—bombs that cascade submunitions over an area approximately the size a football field—as well as scatterable land mines, which can detonate at random intervals or by multiple inputs from human steps, making them especially deceptive and dangerous in civilian locales. Both weapons are proscribed in widely ratified international conventions. The 2008 Convention on Cluster Munitions, which prohibits the use, development, acquisition, or stockpiling of this weapon under any circumstances, counts 110 signatories. And there are 164 states party to the 1997 Anti-Personnel Landmines Convention, which bans all antipersonnel land mines, scatterable or otherwise. Russia, like China and the United States, has not signed either treaty. (Under one interpretation of international law, that does not matter: the conventions’ wide ratification allows them to rise to the level enforceable customary law. Even if one does not take that view, Russia’s use of these weapons to inflict maximum harm on civilians is clearly a war crime.)

This is just one thread of the emerging story of war crimes in Ukraine. There are the images out of Bucha, which show Russian soldiers executing unarmed Ukrainians, in addition to reports of sexual assault by Russian soldiers against Ukrainian women and girls. The UN’s Office of the High Commissioner of Human Rights recorded 12,584 civilian casualties in Ukraine from February 24 to July 31, mostly due to shelling from heavy artillery and multiple-launch rocket systems. The actual figures, as that office acknowledges, are certainly much higher; a thorough documenting of casualties has not been possible in locations where fighting has been especially intense. In a recent report, the Ukrainian nongovernmental organization (NGO) Truth Hounds assembled evidence of war crimes and other violations of international humanitarian law during the Russian offensive in late May, including the shelling of apartment buildings and other civilian infrastructure in Mariupol and the forced displacement of civilians into “filtration” camps from which they are then deported into Russia. In a recent article in the New Yorker, Masha Gessen highlights the work of Truth Hounds and offers in-depth portraits of several Ukrainian victims of the conflict.

The evidence doesn’t stop there. The Atlantic Council’s Digital Forensics Research Lab has reported that in the assault on Mariupol in May, incendiary munitions were deployed in civilian areas, in clear violation of Protocol III of the UN’s Convention on Certain Conventional Weapons, to which 125 states, including Russia, are party. A phone conversation between two Russian soldiers intercepted by the Ukrainian Security Service captures the attitude on the ground:

Soldier 1: We’re waiting, everyone’s waiting. . . for Volodya [Putin] to get fucking sick of it, he withdraws troops and throws Topol’s [ICBMs] in here. . . .

Soldier 2: Yeah? Haha. Waiting?

Soldier 1: Otherwise, anything that’s forbidden by the international convention—cluster bombs phosphorous. . . .

Soldier 2: It’s all working!

Soldier 1: . . . we are allowed them. We’re launching all of it there.

Soldier 2: They allowed you, too?

Soldier 1: Yes!

According to Gessen, indiscriminate attacks on Ukrainian civilians show that “Russian troops seem to believe that this is just how war works.” That gives them too much credit. If accurate, this conversation between Russian soldiers reveals knowing and intentional violation of international conventions—violations permitted by their superiors.

The problem is not that Russia has a history of repudiating international humanitarian law. The country has signed many of the treaties in the Geneva tradition and was one of the initial signatories of Additional Protocol I (1977), which governs international armed conflicts. Its own 2001 Regulations on the Application of International Humanitarian Law declare that “under any circumstances, international humanitarian law ensures humane treatment during an armed conflict of persons not directly involved in combat operations.” In fact, Russia has some historical claim to leadership on these issues: Czar Nicholas II was a major promoter of the Hague Conventions, which marked the inauguration of modern laws of armed conflict. The problem is that Putin and his cronies are flouting Russia’s commitments in treaties and in its own domestic law.

The crimes that an international tribunal might consider are obvious enough. Russia’s unprovoked violation of Ukrainian sovereignty is a clear-cut case of the crime of aggression, defined in international law as the use of armed force by a state against the sovereignty, territorial integrity, or political independence of another state. The record thus far indicates that Russia is intentionally terrorizing civilian populations; by any measure, that is a war crime. And the frequency and intensity of Russia’s attacks on civilians may rise to the level of a crime against humanity, legally defined as certain acts committed as part of a widespread or systematic attack on a civilian population. Russia’s actions—murder of civilians, sexual crimes, forced deportation—may even meet the standards of the crime of genocide: actions committed with intent to destroy, in whole or in part, a national group as such.

The last two major conflicts in Europe, World War II and the Yugoslavian wars, each occasioned a significant advance in international criminal law. By all appearances, the war in Ukraine will do the same. Thanks to the work of the UN and NGOs like Amnesty and Truth Hounds, a thorough record of war crimes is already emerging—a vital first step toward accountability. More significant still has been the early involvement of the International Criminal Court (ICC) through the Office of the Prosecutor, Karim Khan, who was appointed in 2021. International tribunals are typically assembled at the end of a conflict and tasked with transforming piles of rubble into actionable evidence. Ukraine will be different. Already on the ground, Khan’s office will have at its disposal a more thorough and authoritative body of evidence than has ever existed for an armed conflict, and so far there is broad international support for ICC action. The question is what happens next.

Another war, another heap of war crimes. It is easy to be cynical, or at least fatigued, by the past quarter-century’s parade of international conflicts. At the end of its report on Kharkiv, Amnesty calls on “all national and international institutions with jurisdiction over the crimes committed in Ukraine . . . to take steps to ensure that evidence is collected and preserved so that those most responsible are brought to account in fair trials.” To many ears this will sound more like a rhetorical flourish than a practical call to action—a demand, history shows, that routinely fails to hasten the arrival of justice.

Calls for accountability can also sound behind the times. Trying war criminals had its heyday in the 1990s, when broad international support—and the imprimatur of the UN Security Council—backed a tribunal on atrocities in the former Yugoslavia. The successes of the International Criminal Tribunal for the former Yugoslavia (ICTY) paved the way for the formation of the International Criminal Tribunal for Rwanda (ICTR), also with the support of the Security Council. The latter has had more mixed success, as has its counterpart in Sierra Leone. The mood favoring criminal accountability in the late ’90s ushered in the creation of the ICC through the Rome Statute, the first text of which was drafted in 1998 and which came into force in 2002. Since then, Rome parties have not been especially invested in supporting the ICC, and the court has been the target of criticism—for the quality of its judges, for unduly targeting African countries, for the length and expense of its proceedings. Responding to these and other concerns, the Assembly of States Parties to the ICC initiated an independent expert review in 2019.

According to the Yamashita standard, commanders are obliged to assure that subordinates respect the laws of armed conflict.

In light of this embattlement, the current push for accountability in Ukraine could mark a moment of significant revitalization for international criminal law generally and for the ICC in particular. From the outset of Russian aggression in Crimea and the Donbas, Ukraine has welcomed the court’s presence—something never done before by a state in active international conflict. While not a party to the Rome Statute, Article 12 allows a non-member to accept the court’s jurisdiction; Ukraine did so in 2014 and again in 2015. The latter declaration was open-ended and had not closed by the time of the Russian invasion earlier this year. The Office of the Prosecutor did not open an investigation in 2014 or 2015, but on February 28 of this year Khan announced that he would seek authorization to do so, and his office has now set up field offices in Ukraine. This effort was significantly bolstered by a group of Rome parties that referred the situation in Ukraine to Khan’s office. With Lithuania leading the charge, the referral rapidly became the joint effort of 43 states (including NATO members Canada, France, Germany, and the United Kingdom)—an unprecedented side-stepping of the UN in a broad international push for an ICC investigation.

Under the ICC’s principle of complementary jurisdiction, Khan will work in tandem with Ukraine’s domestic courts, the latter focused on charges against rank-and-file Russian soldiers and low-level officers. Some trials of this sort are already taking place. On May 23 a Ukrainian court sentenced Russian Sergeant Vadim Shishmarin to life in prison for violating the laws and customs of war. Meanwhile the Office of the Prosecutor General of Ukraine has recently identified and is proceeding to try a Russian soldier suspected of rape and is investigating a senior lieutenant who ordered his troops to fire on unarmed civilians.

The ICC, for its part, will do what Ukraine’s domestic courts are unwilling or poorly equipped to do. This may include bringing charges against Ukrainian officers; concerns have already been raised about their habit of staging counter-offensives from within civilian areas, a clear Geneva violation. But the real focus will be on Russian command. The ICC angles for big fish. Just how big will Khan go? Given the nature of the crimes involved—and the unique standards of criminal culpability that apply to commanders of armed forces—he just might pursue Putin himself.

Whatever actions the ICC takes, the United States will remain on the sidelines, having withdrawn from the Rome Statute in 2002. Even if the U.S. government wished to support the ICC’s efforts in some way, it is hamstrung by the 2002 American Servicemembers’ Protection Act—a legacy of the late Senator Jesse Helms—which contains sweeping language barring the government from providing the court with money or personnel. The act goes so far as to authorize the president to use “all means necessary” to release any U.S. person detained by the ICC; hence its derisive nickname, the “Hague Invasion Act.” (A bill to repeal this law was introduced in the House of Representatives in April this year; it has not left the House Committee on Foreign Affairs.)

At the same time, the legal resources deployed in charges of superior responsibility have an important American provenance. The practice of holding criminal trials for the architects of a brutal military campaign took shape after World War II. At Nuremberg that meant the prosecution of Hermann Goering, then the highest-ranking Nazi still alive. The Japanese case was more complex. Emperor Hirohito maintained his position (if only symbolically) as part of the peace being negotiated, and former Prime Minster Hideki Tojo would be tried in the Tokyo Tribunal in 1946. Before that tribunal was convened, Tomoyuki Yamashita, a general in the Imperial Japanese Army and military governor of the Philippines, was tried in proceedingsthat did little to dispel the impression of an exercise in victor’s justice. He was brought before a military commission directly under the authority of General Douglas MacArthur, commanding officer of the Allied forces that had just liberated the Philippines. MacArthur saw to it that the guilty verdict was delivered on the fourth anniversary of the attack on Pearl Harbor.

Through counsel, Yamashita objected to every aspect of the trial. Among other things, he claimed that he could not possibly be held accountable for actions undertaken in the heat of battle by all of the soldiers under his command, many of them at great geographical remove. The charges alleged, in particular, that he “failed to discharge his duty as commander to control the operations of the members of his command, permitting them to commit brutal atrocities and other high crimes.” In other words, Yamashita stood accused not of doing something but of allowing something to happen. This may sound like ordinary criminal negligence, but making that charge might have imposed an unwelcome burden of proof, potentially opening the door to mens rea arguments. Instead of going that route, the prosecution simply entered the horrors of the Japanese occupation into the record—through witness testimony and hearsay—and rested their case. Yamashita’s defense thus had some reason to claim that he was “not accused of having done something or having failed to do something, but solely of having been something, namely commander of the Japanese Forces.”

These objections were brought before the U.S. Supreme Court. Many American jurists consider the resulting decision, In re Yamashita (1946), to be one of the Court’s wartime embarrassments. (In a 2014 book, for example, Allan Ryan describes it as “convoluted and erroneous” and chides the Court for neglecting to invalidate a “conviction that was obtained in violation of the laws of the United States.”) In their dissenting opinions, Justices Frank Murphy and especially Wiley Rutledge, Jr., capture now-orthodox views. Murphy remarks on the Yamashita trial’s “needless and unseemly haste” and strenuously objects to the kind of superior responsibility that the Court sanctions in its opinion. Charging Yamashita with “permitting” atrocity, Murphy argues, opens a Pandora’s box: “No one in a position of command in an army, from sergeant to general, can escape [its] implications. Indeed, the fate of some future President of the United States and his chiefs of staff and military advisers may well have been sealed by this decision.” Rutledge, for his part, worries that the culpability standard is far too malleable: Could Yamashita really be expected to be aware of, much less accountable for, the actions of all his soldiers in the midst of war? Hostilities had ceased, even if a formal peace with Japan had not yet been signed, so the deviations from due process in Yamashita’s trial ran afoul of the principle that “the Constitution follows the flag.” (Rutledge also objected to the Nuremberg trials on due process grounds and felt that the participation of his colleague, Robert H. Jackson, was an affront to the dignity of the Supreme Court.)

But there is another story to tell about In re Yamashita. Despite its disgraced status in U.S. law, it has had an enormously positive impact in international law—perhaps far more than any other decision of the U.S. Supreme Court, which tends, as in its death penalty decisions, to lag behind international standards of justice. Justice Harlan Stone’s opinion for the majority articulated standards for superior responsibility that have come to be known as the Yamashita principle: “the law of war presupposes that its violation is to be avoided through the control of the operations of war by commanders who are to some extent responsible for their subordinates.” In other words, since commanders are, by definition, in a position of command, they are obliged to assure that subordinates respect the laws of armed conflict. The principle does not depend on evidence that a commander was directly involved in war crimes, or even that they had been reported to him.

Khan’s office will have at its disposal a more thorough and authoritative body of evidence than has ever existed for an armed conflict.

The idea has become customary international law, a rule obligatory even if a state has not acceded to it in a treaty: a superior is criminally liable if he or she knows, or has reason to know, of offenses committed by subordinates and fails to take reasonable steps to prevent or punish those violations. The “reason to know” provision has had various specifications. Additional Protocol I of the Geneva Conventions comes close to imposing the requirement of evidence that a superior knew of breaches, holding superiors responsible “if they knew, or had information which should have enabled them to conclude in the circumstances at the time” that a subordinate was going to commit a breach. The official commentary on this article, issued in 1987, softens this position. Pointing to the tribunals following World War II, it makes clear that a superior cannot “wash his hands of an affair” simply by “maintaining that he was not aware of the breaches committed.” In “flagrant cases . . . a knowledge of breaches committed by subordinates could be presumed.”

The “reason to know” provision has thus come to mean something like an ordinary negligence standard, according to which a failure to act—given the nature of one’s office and the situation in which one finds oneself—marks a gross deviation from the standard of care that can be expected of a reasonable person. But the standard is slightly lower than ordinary negligence, in recognition of the extraordinary nature of crimes committed in conflict and the special burden of responsibility attached to commanders of armed forces. International law has intentionally eschewed bright-line rules and opened a space for tribunals to engage in both factual analysis and subjective evaluation. The legal consensus now veers toward the prospect shocking to Yamashita’s lawyers: superiors can be convicted not for doing something but for being something, because being that thing makes one guilty of failing to prevent and punish violations.

This principle is echoed in the statutes of the ICTY, the ICTR, and the Extraordinary Chambers in the Courts of Cambodia for the Prosecution of Crimes Committed under the Khmer Rouge. It also appears in military manuals and statute law in every corner of the world. The Australian Defence Force’s Manual on Law of Armed Conflict (1994), for example, refers explicitly to the “Yamashita principles,” which it takes to apply not only when a commander knows that war crimes are about to happen, or have happened, but also when a commander “should know subordinates are going to commit war crimes and does not prevent them” or “should know subordinates have committed war crimes and does not punish them.”

Military handbooks naturally focus on military command, but international tribunals, statutes, and case law equally apply the Yamashita principle to civilian superiors in a position to exercise effective control over their subordinates. This standard will certainly be relevant to any charges the ICC pursues in Ukraine. Article 28(a) of the Rome Statute cleaves closely to the Yamashita principle, specifying that a superior is criminally responsible for crimes “committed by forces under his or her effective command or control” when that superior “either knew or, owing to the circumstances at the time, should have known that the forces were committing or about to commit such crimes.”

On this basis, charges of aggression and other war crimes could well go all the way to the top: not just to military leadership, but to Putin’s ministers and even to Putin himself. The available evidence suggests we could be on the brink of a major advance for the ICC: the trial of the leader of a major world power. And not just any world power, but one with a permanent seat on the UN Security Council. Because the ICC is independent of the UN, it cannot be frustrated by a Security Council veto. What’s more, since this war is not likely to result in the fall of Moscow, proceedings would look a lot less like an exercise in victor’s justice than was the case with Germany and Japan after World War II.

But the ICC is a court without a police force. If charged, Putin and his inner circle would have to turn themselves in or be arrested by a state willing to hand them over. The court’s pursuit of Sudan’s Omar al Bashir illustrates what might happen in such a scenario. The ICC first issued an arrest warrant for al Bashir in 2009. He remains at large and was able to travel to Saudi Arabia and Egypt in 2015, despite court-issued requests to both countries that he be arrested and surrendered. Neither state is party to the Rome Statute, but Jordan is, and al Bashir traveled there in 2017. The result has been a long and ongoing bit of diplomatic tussling that has no hope of resulting in the arrest of al Bashir.

An ICC warrant for Putin would likely play out in similar fashion. He would be arrested neither at home nor on the soil of allied nations. He may even turn up at a meeting of the G20, as a dare to the host nation. The court would file request after request that goes unheeded, allowing Putin to varnish his favored image of muscular defiance of the West.

I spoke to a former senior official in the Obama and Biden administrations about these issues. While he expressed broad sympathy with the aims of the ICC and favored some form of U.S. support of its activities, he also had reservations about the court’s effectiveness and the professionalism of past prosecutors and judges. In his telling, significant advances in accountability are attributable in no small part to the United States: “When the United States has participated in international tribunals, like in the former Yugoslavia and Rwanda, they have been a success, because they have had access to U.S. resources and DOJ prosecutors.” The ICTY had some leverage against states involved in the Yugoslavian wars, which saw participation as a first step toward EU membership. Russia has no desire to join the EU, and the EU no desire to admit Russia. Taking on a hostile Russian leadership, this U.S. official argues, could “break” the court. Putin and his ministers would simply ignore the ICC, travel freely at home and in friendly states, and show the world that the reach of the court is not nearly so international as it pretends.

The point of seeking accountability is to end impunity, not to achieve perfect deterrence. And efforts on behalf of justice are not zero-sum.

To take that point further, one can readily imagine how charges against Russian leadership might be interpreted as a case of “lawfare,” the use of legal means to achieve strategic geopolitical objectives. Russia and its allies will vigorously portray the court as an instrument of NATO—advancing the West’s ambition of isolating and weakening Russia rather than standing for the equal application of impartial law. And they will point to the court’s inaction after the 2003 U.S. invasion of Iraq, where U.S. forces were known to have engaged in torture and to have used cluster bombs and incendiary weapons.

But there are other views to take. Geoffrey Robertson, former president of the War Crimes Court in Sierra Leone, has pointed out that given Putin’s age, there is ample time for the political situation to shift in ways that might prompt Russian authorities to send him on a one-way trip to The Hague. I also spoke to Louise Arbour, former chief prosecutor of the ICTY. Milošević was still in power when she issued an indictment against him in May 1999. It was far from certain that he would appear for a trial, she noted, but, somewhat amazingly, his own government shipped him off to The Hague within eighteen months. Arbour added that prosecutors should avoid geopolitical prognostication, especially in unpredictable and fluid situations: “We are not politicians. We are at our best when we play our long suit, which is application of the law.” And she noted that evidence has a shelf life: witnesses do not live forever, and they may change their minds about testifying or be influenced or intimidated to withdraw their testimony. At the same time, Arbour cautioned that a prosecutor must act “in the interests of justice, which includes the interests of the institution.”

This would suggest that the Office of the Prosecutor ought to hold off if charges against Putin or other Russian leaders would further weaken the ICC. But signs appear to be pointing in precisely the opposite direction. As the multilateral referral to Khan’s office makes clear, dozens of states are invested in seeing the ICC take action and are mobilizing themselves accordingly. That is precisely the kind of state-level support for the court’s mission that has been wanting in recent decades and will strengthen it as an institution. Given the broad support behind the referral of Ukraine to Khan’s office, would the court really make new enemies? Russia, China, Israel, and the United States have long been hostile to the court; it is hard to see how exercising jurisdiction in Ukraine would further damage these relationships, or what new ways of expressing hostility these states will concoct. Finally, it is well-known that the court has no police force; Putin’s evasion of an arrest warrant will not alert the world to a weakness hitherto unrecognized.

Others might object that prosecuting Putin won’t end war crimes or bring about world peace, so it must be a distraction—strategically, maybe even morally. But this deeper skepticism misunderstands the function of international law. The point of seeking accountability is to end impunity, not to achieve perfect deterrence. And efforts taken on behalf of justice are not zero-sum.

They also take time. Nuremberg was not so long ago, historically speaking. The ICTY was expensive and slow moving, but between 1993 and 2017 it sentenced 91 perpetrators and architects of atrocity crimes. Those sentences did not prevent genocide in Rwanda or Sudan, but they nonetheless serve several purposes. They present for posterity an archive of atrocity crimes tried under due process. They show that an international legal order can be advanced with sufficient investment from the international community. They indicate that statesmen and generals are not above the law. And they prove that Cicero got it at least a bit wrong: when arms speak, the laws are not entirely silent.

The conflict in Ukraine grinds on. We may yet be several years away from a cessation of hostilities and from any summons to appear before the ICC. But it is promising that Khan is doing the most important thing he can do for now: assuring that should Putin arrive in The Hague, he will be greeted by a mountain of evidence against him.

Boston Review is nonprofit and relies on reader funding. To support work like this, please donate here.