Stunning new details emerged Friday on the largest prisoner swap since the Cold War, with the Kremlin acknowledging for the first time that some of the Russians held in the West belonged to its security services — and the children of a Russian couple posing as spies only learned their true nationality on the flight to Moscow.

Kremlin spokesman Dmitry Peskov confirmed that a detained couple released in Slovenia —Artem and Anna Dultsev— were undercover intelligence officers commonly known as “illegals.” Posing as Argentine expats, they used Ljubljana as their base since 2017 to relay Moscow’s orders to other sleeper agents and were arrested on espionage charges in 2022.

Their two children joined them as they flew to Moscow’s Vnukovo Airport from Ankara, Turkey, where the mass exchange took place. The children don’t speak Russian, and only learned their parents were Russian nationals sometime on the flight, Peskov said.

They also didn’t know who President Vladimir Putin was, “asking who is it greeting them,” he added.

“That’s how illegals work, and that’s the sacrifices they make because of their dedication to their work,” Peskov said.

A total of 24  prisoners were involved in Thursday’s historic swap —and a total of 26 people, including the spy couple’s kids, changed planes on the tarmac in Ankara.

While journalists Evan Gershkovich and Alsu Kurmasheva and former Marine Paul Whelan were greeted by their families and President Joe Biden in Maryland on Thursday night, Putin embraced each of the Russian returnees at the airport and promised them state awards and a “talk about your future.”

Also returning to Moscow was Vadim Krasikov, a Russian assassin who was serving a life sentence in Germany for the 2019 killing of a former Chechen fighter in a Berlin park. The German judges who sentenced Krasikov called Khangoshvili’s murder an act of Russian “state terrorism,” and the incident set off a diplomatic row between Moscow and Berlin.

Peskov told reporters Friday that Krasikov is an officer of the Federal Security Service, or FSB —a fact reported in the West even as Moscow denied state involvement.

He also said Krasikov once served in the FSB’s special forces Alpha unit, along with some of Putin’s bodyguards.

“Naturally, they also greeted each other yesterday when they saw each other,” Peskov said, underscoring Putin’s determination to include Krasikov in the swap. Earlier this year, Putin stopped short of identifying Krasikov, but referenced a “patriot” imprisoned in a “U.S.-allied country” for “liquidating a bandit” who had killed Russian soldiers during fighting in the Caucasus.

The large-scale exchange comes less than two years after WNBA star Brittney Griner was traded for Russian arms dealer Viktor Bout, who was nicknamed the “Merchant of Death,” on an airport in Abu Dhabi. 

Griner was arrested in 2022 at a Moscow airport when vape canisters containing cannabis oil were found in her bags. She was sentenced to nine years in prison on drug charges. 

Arrested in 2008, Bout was serving a 25-year prison sentence in the U.S. for conspiring to sell weapons to people who intended to kill Americans.