The Russians fled quickly from Cherneshchyna, abandoning their positions in a panic and disappearing into the night to escape the Ukrainian advance. “On the morning of Oct. 2, they were just gone,” says Oleksiy, a resident of this small village on the eastern edge of the Kharkiv region, where a sudden Ukrainian counter-offensive made Russian soldiers flee without a fight, leaving behind ammunition boxes, propaganda newspapers, and empty vodka bottles in their trenches and foxholes.

But in Cherneshchyna—as in many other towns and villages across the region—it wasn’t just the Russians who fled as Ukrainian forces secured bridgeheads on the west bank of the Oskil river and liberated a string of settlements in a lightning-fast advance. Dozens of villagers—who had either sympathized or openly collaborated with the invaders—joined the flight too.

Three weeks on, the fighting is not yet over in the area. Artillery fire still booms out as Ukrainian troops push on into the neighboring Luhansk oblast. But whatever happens on the battlefield, life here, and in other liberated towns and villages in eastern and southern Ukraine, will never return to normal until there has been a reckoning—between those who collaborated with the Russians and those who resisted.

According to Oleksiy, a former mechanic who had fled the fighting in Izyum, as many as one-third of the 700 residents of Cherneshchyna were either collaborators or Russian sympathizers. The priest officiating at the local St. Nicholas Church—affiliated with the Moscow patriarchate—was reportedly among those who fled the advancing Ukrainian troops. “He scampered to Russia, and stole some of the icons from the church,” laughs 35-year-old Olena, Oleksiy’s wife.

As Russian troops and armored vehicles poured into towns and villages across the country, many, like Oleksiy and his family bided their time, waiting for the moment they could come out and greet advancing Ukrainian soldiers with the blue and yellow flag they had kept hanging on the clothes-line—despite being ordered to take it down by Russian soldiers. “We never doubted, we knew that Ukraine would take back Cherneshchyna, and we waited,” says Olena. Her husband chimes in: “The Ukrainian soldiers told us ‘You guys are fearless’ when they saw that we had kept the flag outside.”

Yet, others chose to collaborate with the Russians, out of greed, fear, or ideological conviction.

While Oleksiy tells us that Ukraine’s security service has not yet made it to the village, local police have already been hard at work to identify and detain suspected collaborators. Twenty miles east of Cherneshchyna, in the village of Horokhovatka, a 30-year-old resident was arrested on Wednesday by local police. The man is suspected of having provided food to the Russians and of having denounced his neighbors harboring pro-Ukrainian views to the occupiers—a move with potentially deadly consequences, as Russian soldiers routinely abducted, tortured, and murdered pro-Ukrainian activists, residents, and local officials.

The man—who faces up to 12 years in prison if convicted—is among the hundreds of Ukrainian citizens currently facing criminal proceedings for having provided help to Russian forces. As of Sept. 16, 1,358 similar cases had already been opened against individuals and local officials throughout the country, according to the head of Ukraine’s National Police, Ihor Klymenko.

In liberated settlements, retribution is at hand for those suspected of having collaborated with the enemy. On a Facebook post celebrating the liberation of the town and the surrounding villages, the city council of Borova claimed that a number of Russian sympathizers had already been detained by law enforcement agencies, adding that in the nearby village of Izyumske, the house of the collaborator and self-appointed “elder” (mayor) had burned down “as a result of spontaneous combustion.” According to the Kharkiv Anti-Corruption Center, this local gym teacher and member of the local soccer federation had called a community meeting in April, during which he proclaimed himself mayor of the village and had set to work on preparations for a “referendum” on annexing the region to Russia.

While the self-proclaimed mayor’s current whereabouts are unknown, his name and information have already been published on the Myrotvorets website, a database of people deemed to be “enemies of Ukraine” by the secretive team behind the project.

Meanwhile, a local Telegram channel titled “TRAITORS” has been busy publishing the identities of civilians and local officials suspected of having helped the occupiers in Borova and the surrounding region. Among them, a husband and wife from the nearby village of Pisky-Rad’kivs’ki, who are accused of having worn the St George’s ribbon—a Russian military symbol now associated with support for the invasion of Ukraine—and of having allowed Russian forces to station their vehicles in their backyard. A slew of similar channels—some of them with tens of thousands of subscribers—have popped up during the first weeks and months of the occupation, documenting the identities and alleged offenses of suspected collaborators, and posting them online.

In Cherneshchyna, locals say, the Russian sympathizers all left in a hurry. “Had they stayed, well, they wouldn’t be here anymore,” says Mikhail with a grin. The young man in his twenties tells us how Russian soldiers had searched him and other residents for nationalist tattoos, as part of a systematic effort to root out “Nazis” and “Banderites” in the area. Mikhail says Vladimir Putin’s soldiers detained and tortured people in the basement of the local school, hoping to extort information from them on the positions and movements of Ukrainian forces.

In the occupied territories of Ukraine, dozens of collaborators have already met their end at the hands of local partisans, sometimes acting in concert with Ukrainian special services, as military officials have confirmed. And as the Ukrainian Armed Forces liberate towns and villages across the eastern and southern regions of the country, some of their brutalized residents could be tempted to dish out swift, extrajudicial retribution of their own. Already, experts warn that vigilante groups may try to seek revenge for Russia’s war crimes—and against the people who abetted them.

For a Frenchman, who now lives in Ukraine, there is a clear historical precedent. As a student in France, I learned about the brief but violent episode of the épuration sauvage—the “unofficial purge”—when in the immediate aftermath of the country’s liberation from German occupation in 1944, the people of France settled their scores with those who had collaborated with the Nazis. Members of the Milice—Vichy France’s vicious paramilitary organization that had helped to round up Jews and résistants—were summarily executed, while women who had slept with German soldiers had their heads shaved and were paraded in front of jeering crowds. While some of the initial estimates were vastly overblown—sometimes in an attempt to rehabilitate collaborators and Nazi sympathisers—the most recent put the number of extrajudicial executions during the épuration at roughly 9,000.

Perhaps the onus should not fall on Ukraine alone to ensure that Russian war criminals and the people who helped and enabled them are held accountable. There should be a process that is thorough, transparent, and internationally accountable. Lest the people take the matter into their own hands, once again.