The landmark prisoner swap between Russia and the United States included Paul Whelan, a former U.S. Marine incarcerated for more than five years after an espionage conviction that he and the U.S. government long maintained was a sham.

Whelan was arrested by Russian authorities in December 2018, and his family had grown increasingly frustrated that long-running diplomatic efforts between Washington and Moscow had failed to secure his release as part of previous exchanges.

Whelan, 54, enlisted in the Marine Corps in 1994 as an administrative clerk and served for 14 years, including two wartime deployments to Iraq, according to his official service record reviewed by The Washington Post.

His time in uniform ended unceremoniously after a conviction in military court for larceny and other crimes, resulting in a bad-conduct discharge, the Marine Corps said.

Whelan – a citizen of the United States, Canada, Britain and Ireland – later began a career in corporate security. At the time of his arrest, he worked for a Michigan-based automotive parts supplier with business contracts in Russia.

He was a regular visitor to the country, his brother and friends have said.

Whelan was in Russia in late 2018 to attend a wedding. Russian Foreign Minister Sergei Lavrov accused him at the time of being caught “red-handed” on a spy mission where he was to retrieve a flash drive containing sensitive information.

Whelan maintained throughout the trial that he was framed. His attorney, Vladimir Zherebenkov, said his client unwittingly received “state secrets” on the drive, which he thought contained holiday photos from a friend.

The timing of his arrest, two weeks after a Russian national pleaded guilty in U.S. federal court of acting as a foreign agent, fueled speculation that Whelan was to be used as a bargaining chip.

In 2020, he was sentenced to 16 years of hard labor in a Russian prison colony.

Whelan and his family have made consistent appeals to the U.S. government to secure his release. But he has languished in prison as Washington secured the release of other high-profile prisoners, including WNBA star Brittney Griner and Marine veteran Trevor Reed, who was imprisoned in what U.S. officials considered trumped-up charges.

“It’s extremely stressful knowing that I could have been home years ago,” Whelan told the BBC last year, as he entered his fifth year in confinement. “It’s extremely frustrating to know that they’ve made these mistakes. They’ve basically abandoned me here.”

Linda Thomas-Greenfield, the U.S. ambassador to the United Nations, called on Russia to release Whelan, accusing Moscow in July of treating “human beings like bargaining chips.”