It's been almost two years since Sasha Radchuck, then 11, pleaded with Russian soldiers not to separate him from his mother at what was called a "filtration camp" in Russian-controlled eastern Ukraine, where they had both been forcibly resettled after being forced from their home in besieged Mariupol. 

He still talks of his mother in the present tense, but hasn't seen or spoken to her since April 2022. 

"My mom is very beautiful," he said through a translator. "To every son, his mom is the best and most beautiful. For me, my mom is the best." 

Now 13 and since reunited with his grandmother, Sasha is urging world leaders to press Russia to stop its practice of what the International Criminal Court deemed to be "unlawful deportation" -- a legal term for stealing children amid war. 

"I go around the world to tell about my mom," he said. "So maybe someone in the U.S. can hear me and help find her."

Sasha is not alone. Ilya Matvienko, 11, and 14-year-old Kira Obedinska faced similar horrors in Ukraine. The trio told leaders at the United Nations in New York last week that Russian soldiers took them captive after the siege of Mairupol, and had planned to send them to live with Russian families. 

But they count themselves lucky, and are just three of 388 that have been reunited with loved ones. According to an estimate from the Ukrainian government, there are nearly 30,000 kids that have been forcibly removed or deported from their homes. 

Russia, for its part, claims it is rescuing children as a humanitarian gesture. Maria Lvova-Belova, the head of what Russia calls its children's rights program claims 700,000 kids have been taken in on a humanitarian basis. 

Russian state TV has broadcast images of Vladimir Putin and children it claims were "rescued" by soldiers from Mariupol. But Ukraine's government argues that Russia's plan is to erase Ukrainian identity — first it creates orphans, then it steals them.

Ilya was just 9 years old when he became an orphan. He watched his mother die from a shrapnel wound to the head. A neighbor buried her in the backyard. Ilya was also hit by the shrapnel and his leg was badly wounded. Traumatized and unable to walk, he said Russian soldiers took him to a hospital where he was operated on without anesthesia. Yet amid the trauma, his doctors coached him to praise Russia. 

"You must say, not glory to Ukraine, but glory to Russia," Ilya said his doctors told him. 

Ilya's grandmother told CBS News that she spotted her grandson in a Russian propaganda video, speaking from a hospital bed, and described a complex network of people who helped her get him back.

Kira's grandfather said that after his son died in a bombing, he feared he'd never see Kira again. The 14-year-old described to CBS News the painful details of hiding in underground shelters and trying to survive the warzone.

Kira, Ilya and Sasha's grandparents shared details of how they came to rescue the children, and mentioned receiving some Ukrainian government help but CBS News cannot independently confirm those details. The government in Kyiv claims the details are classified. 

Ukraine's government is urging these children to share with the public what happened to them. The children were accompanied to the U.S. by Daria Herasymchuk, Ukraine's Presidential Commission for Children's Rights and Child Rehabilitation.

Their visit to the U.S., coordinated with the Ukrainian government, was sponsored by Builders Ukraine, a U.S.-based non-profit. It partnered with BlueCheck and TAPS to launch the Courage Project, which is seeking signatures for a petition demanding the release of stolen Ukrainian children. 

Ilya said he wants other countries to know the reality of what is happening in Ukraine, "that it's not a fairytale, that's really happening." 

Stealing children in times of war — "forced deportation" as the International Criminal Court calls it — is a war crime. The act of deporation and transfer can, in some cases constitute a crime against humanity and a component act of genocide. 

In 2023, the ICC issued arrest warrants for both Putin and Lvova-Belova. 

Nathaniel Raymond is the executive director of the Yale Humanitarian Research Lab, which leads a U.S. government-funded initiative to track down Ukraine's stolen children, and says he's seen evidence of Russia giving some older children military training. 

"We have not yet seen evidence of the children being deployed in combat," he said. "But we have seen systematic efforts to turn them into soldiers."

Raymond compared taking children to use of a nuclear weapon — one of the most destructive and dangerous acts imaginable, and warned of the dangerous precedent that could be set if Russia is not stopped.

"It gives the green light to children being abducted in the wars of tomorrow," Raymond said. "It says that the international community will not stop kidnappers."

But sources told us that in recent months it has gotten harder to get kids back; and now with U.S. financial support for Ukraine's war effort in question, it may also imperil international recovery efforts.

The children also met with U.S. officials during their visit to Washington. The State Department told CBS News that the U.S. government's assessment is that there is "a systemic nature to Russia's deportation system and efforts to obstruct the return of Ukraine's children."

Despite the ICC arrest warrants for Putin and Lvova-Belova, there is no unified international body that has attempted to negotiate the return of the children. Russia maintains veto power at the UN and finds willing international partners to help it defy isolation and sanctions. 

Sophia Barkoff and Camilla Schick contributed reporting. 

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• Ukraine
• Russia

Margaret Brennan

Margaret Brennan is moderator of CBS News' "Face The Nation" and CBS News' chief foreign affairs correspondent based in Washington, D.C.