In October 2022, Ukrainian pupil Diana's teacher came into the classroom and told everyone to fill in some paperwork: they were being sent to Crimea to continue their studies in a Russian-run school.
The sudden transfer from their hometown of Kherson came towards the end of the Russian occupation of the vital port city, which Moscow held from March to November 2022.
Buses whisked the children away for the trip south to Crimea. Diana's younger brother and sister were with her.
“We were told to cover the windows on the bus and turn off the phones,” 15-year-old Diana, who asked that her last name not be used, told The National.
“We were told not to look out the windows. It was weird, like we were some secret or something like that.”
Russia invaded Crimea in 2014 and has held it ever since. In February 2022, Moscow launched its full-scale invasion of Ukraine in a bid to claim the entire country, seizing large parts of the east in a bloody conflict that continues unabated today.
During the intervening two years, Ukraine says Moscow has forcibly transferred about 20,000 children into Russia or Russian-held territory.
Children like Diana who escaped or who were released say they were kept in crude conditions in Russian re-education centres, where they were given Russian documents and taught that they were Russians who had been liberated from Ukraine's ruling “Nazis”.
Russian President Vladimir Putin has long claimed that his war aim is to “de-Nazify” Ukraine.
“Sometimes in these camps, the Russian [national] anthem plays three or five hours a day,” said Mykola Kuleba, who heads the Save Ukraine charity that tracks and helps rescue children who have been taken into Russian territory.
“It's systematic brainwashing and systematic indoctrination.”
The Russian embassy in Washington did not respond to requests for comment for this story. Russia has previously said it moved some children for their own protection from the war.
In March last year, the International Criminal Court issued arrest warrants for Mr Putin and Russian Presidential Commissioner for Children's Rights Maria Lvova-Belova for possible war crimes involving the deportation of Ukrainian children.
Russia denies it is forcibly deporting children. Alexey Vovchenko, a deputy minister of labour and social protection, told a UN panel last month that 4.8 million residents of Ukraine – including 770,000 children – had been taken in by Russia.
Mr Kuleba, who served as Ukraine's presidential commissioner for children's rights from 2014-2021, said Russia's aim in deporting children was multifaceted.
Mr Putin “wants to erase our identity”, Mr Kuleba said.
“These children grew up in Ukraine and they knew that Ukraine is a state, it's a nationality,” he told The National.
Moscow is also taking children into its territory and offering significant financial incentives to their Ukrainian families to move along with them, Mr Kuleba said, in some instances offering up to $30,000 to help them buy an apartment in Russia.
Bringing Ukrainian families into Russia who accept Russian nationality also helps address the country's demographic challenges. Russia has a negative population growth rate that has been exacerbated by the war in Ukraine, where hundreds of thousands of young men have been killed or wounded.
Russia “has stolen Ukrainian children in an attempt to steal Ukraine’s future”, President Joe Biden said in a speech in Warsaw a year ago.
Mr Kuleba said Save Ukraine has helped rescue 241 Ukrainian children who had been taken to Russian schools in occupied parts of Ukraine or into Russia itself.
For security reasons, he would not disclose how the group does this. In Diana's case, she said she and her younger siblings were ultimately released after six months, thanks to legal and logistical help from the charity and pressure from her parents.
Diana, who now lives with her family in Kyiv, said her 10-year-old brother was placed in solitary confinement for several weeks after he got into a fight with boys who supported Russia. He was then placed in a psychiatric hospital in Crimea and beaten, she said.
She was one of several children and young adults Save Ukraine brought to Washington this month to bring attention to the issue.
“I came here to tell my story. In order to try to make the world feel this pain of what I have experienced, and I want the other children to have an opportunity to return home and be with their families,” she said through a translator.
Eli Rosenbaum, who in 2022 was appointed by Attorney General Merrick Garland to set up the Justice Department's War Crimes Accountability Team to investigate allegations of Russian war crimes in Ukraine, noted that young minds are easily influenced and said it would be hard for Ukraine to turn back the Russian programming on children who do return.
“The danger, of course, is that children will be turned against their country,” he said.
“If Ukraine, God willing, gets them back, it's going to be very hard to sort of reprogramme them to the truth. These are systematic efforts to 'Russify' these children and other Ukrainians living under Russian occupation”.
Mr Rosenbaum, who retired from the Justice Department last month, is widely known for his work identifying and deporting Nazi war criminals.
He said that the deportation of children, combined with the looting and destruction of Ukrainian cultural and historical sites and statements from Russia's leaders denying the existence of an independent Ukrainian people, amounts to “growing evidence of genocidal intent on the part of Russian leadership”.
Diana and Save Ukraine's visit to Washington comes as Republicans grow in their opposition to sending Kyiv any more financial aid, leaving Ukrainian forces running out of ammunition against renewed Russian offensives.
“It's a national embarrassment, it's a disgrace,” Mr Rosenbaum told The National.
“If the United States won't stand up for a democracy that it has helped to build in Ukraine, then I think it calls into question whether our allies can rely on us.”