(NewsNation) — WNBA star Brittney Griner was been released by Russia Thursday in a dramatic high-level prisoner exchange with the U.S. for notorious arms dealer Viktor Bout, American officials said.

But who is Viktor Bout?

In releasing Bout, the U.S. freed a former Soviet Army lieutenant colonel whom the Justice Department once described as one of the world’s most prolific arms dealers. Bout, whose exploits inspired a Hollywood movie, was serving a 25-year sentence on charges that he conspired to sell tens of millions of dollars in weapons that U.S officials said were to be used against Americans.

According to officials, the former Soviet military officer made a fortune off trafficking weapons, supplying millions of weapons to militias and terrorists around the world, with many of the groups wanting to kill Americans

The so-called “merchant of death” is so notorious he even served as the inspiration behind Nicolas Cage’s character in the 2005 film “Lord of War.”

In 2008, the DEA and Royal Thai Police lured Bout into a sting operation that Bout’s attorney Steve Zissou described as a setup. He maintains that Bout has never had any ties to any terrorist organization.

Bout was serving his 25-year sentence at a federal prison in Illinois, with roughly five years left of his punishment.

Why does Russia want Bout back?

Zissou said that Russia feels like one of its respected citizens was wrongfully targeted by the United States.

“Here in the U.S. [Bout] is the notorious arms dealer. Just like in Russia, Paul Whelan is a notorious spy. In Russia, [Bout] is a respected citizen, who the U.S. government targeted while he was retired and living in Moscow. That is an attack on a country’s sovereignty,” Zissou said in an interview on “NewsNation Prime” back in July.

The Associated Press and NewsNation’s Caitlyn Shelton and Marni Hughes contributed to this report