Kyiv, Ukraine – When the full-scale Russian invasion of Ukraine began, Denys Kostev was 18 and living in an orphanage in Kherson. Appalled by the war, he used to film social media videos decrying the invading Russian forces.

But he was soon forcibly transferred to occupied Crimea, and his rhetoric suddenly went in the other direction.

Now in Kyiv four years later, Kostev told Al Jazeera he played the role of a poster child for wartime Russia just to survive.

Sprightly, eloquent and photogenic, he used to attend a theatre club at his orphanage in the southern Ukrainian city, where he lived after his mother’s incarceration and death.

The experience helped him “star” in numerous videos for Russian television networks – because refusing to be filmed meant risking physical assault or being threatened with jail, he said.

“It was useful to play this pro-Russian role,” said Kostev, who, having ultimately escaped Russia, is now preparing to fight for Ukraine. “I wanted to live.”

But surviving did not come easy, he said.

Kostev’s terrifying journey

Tanks rolled into Kherson days after the war began. People suspected of pro-Ukrainian sympathies were rounded up and interrogated. Some were allegedly abused.

In late 2022, while living in the orphanage, Kostev also studied in a trade school. But as the war intensified, he and others were relocated to the Luchisty (“Full of Sunshine”) summer camp in Russia-annexed Crimea.

“Every morning, you wake up to the Russian anthem, and every Monday, there’s a celebratory hoisting of the Russian flag,” Kostev said of his time there.

The orphans were isolated, he added.

“They’re without parents, no one to explain what’s right or wrong,” he said. “At a certain point, you begin to repeat pro-Russian narratives.”

At least one teenager Kostev met in the camp enlisted to fight against Kyiv, he said.

Ukraine is working to return allegedly abducted children and collect evidence against individuals suspected of being involved in their abduction. More than 2,600 children have returned so far.

The summer camp’s “administration” has not responded to Al Jazeera’s request for comment. Kyiv said that 84 Ukrainian orphans were held there in 2023.

Those who left were among almost 4,000 children forcibly taken from orphanages in Russia-occupied Ukrainian regions, according to Ukrainian rights groups. Kyiv claims that Moscow has herded almost 20,000 Ukrainian minors to Russia to “brainwash” them during the war.

While the Kremlin acknowledges that children are being “re-educated”, it rejects Ukraine’s claims, saying that any children who have been moved were rescued from war zones.

Some of these children lost parents during Russian shelling, and others ended up in “summer camps” after pro-Moscow authorities reportedly convinced their parents to let them go for “safety reasons”.

Ukraine claims that some children were abducted from parents who refused to collaborate with Moscow-installed “administrations” in Russia-occupied areas.

Russian forces and their Ukrainian collaborators have also been accused by Ukrainian rights groups of interrogating and abusing parents – and checking their bodies for pro-Kyiv tattoos or bruises left by recoiling firearms.

‘Deeply disturbing reports’

International rights groups decry the alleged abduction and indoctrination of children as one of the Kremlin’s gravest crimes.

“The physical destruction of this war is visible to everyone, but the campaign to abduct and ‘re-educate’ Ukrainian children as Russian represents something more sinister altogether,” Ivar Dale, a senior policy adviser with the Norwegian Helsinki Committee, a rights watchdog, told Al Jazeera.

“It’s unacceptable,” he said. “There are deeply disturbing reports that Russia is carrying out military indoctrination with a view to use some of these children in the armed forces in their war against Ukraine.”

Some 5,500 young Ukrainians in Russia-occupied areas were sent into Yunarmiya (“Young Army”), a movement that provides military training, according to Ukrainian officials.

The earlier the age, the deeper the transformation of a child’s worldview, according to Svitlana Chunikhina, vice president of the Association of Political Psychologists of Ukraine, a group in Kyiv.

“Children have a flexible psyche; they quickly adapt to a new environment, they mostly trust adults – sometimes involuntarily, but they have no other choice – and take many things for granted,” she said.

That is why they cannot resist Moscow’s narratives, she said.

“But it doesn’t mean that the same will surely happen to all Ukrainian children,” Chunikhina said.

While younger children studied in the camp according to the Russian curriculum, the education system did not appear to have had a thorough, comprehensive programme for teenagers such as Kostev.

Along with his friends, he hung around a Soviet-era compound dotted with cypresses, acacias and evergreen shrubs.

They were not allowed to leave it – but occasionally sneaked out to buy cigarettes and alcohol. Those who were caught drunk were isolated for three days in the hospital and were threatened with prison by the camp’s security chief, a former officer with Ukraine’s special forces who had switched sides, said Kostev, who is now 22.

The idea that the children would “never return to Ukraine” was drummed into them, he said.

In April 2023, after months in camps in Crimea, Kostev was sent back to the occupied southern town of Henichesk – and learned that Russian troops had withdrawn from Kherson seven months earlier.

He enrolled in another trade school and was housed in a squalid, ice-cold dormitory he complained about in a video that went viral.

The next morning, Russia-installed police strip-searched him, claiming he was “spying” for Kyiv and threatened him with jail, he said.

Then he was forced to extol Russia on camera.

In one video, he said he had joined a Kremlin-funded youth movement, wrapped himself in a Russian flag and declared that he wanted to enlist.

But he told Al Jazeera that he was forced and coerced into championing Russia, and had always wanted to leave.

In early 2024, Kostev got in touch with his elder brother and grandmother who had relocated to Germany. He managed to join them and later crossed into Poland, where he spent months awaiting a new Ukrainian passport.

In April, he returned to Ukraine. He said he has attended a military training camp and is now in the early stages of his military career as a drone pilot.

“Wherever you are – home is better,” he said, sitting in a shopping mall in a Kyiv suburb, shortly before air raid sirens forced everyone outside.