In exchange for the release of WNBA star Brittney Griner, the U.S. is releasing infamous Russian arms dealer Viktor Bout.

Bout, 55, had been in U.S. custody for more than a decade and is often known by his two nicknames, the “Merchant of Death” and “Sanctions Buster,” given for his notorious weapons smuggling operation to African and Middle Eastern countries.

Those operations have been the subject of United Nations inquiries and efforts by multiple governments to detain Bout stretching back years, and he was ultimately extradited to the U.S. in 2010 after being detained in Thailand following an international sting operation.

Bout, who has insisted he is innocent, was serving a 25-year prison sentence set to expire in August 2029 on charges of conspiracy to kill U.S. nationals, kill U.S. employees, transfer and use of anti-aircraft missiles and support of a designated terrorist organization.

Moscow for years sought Bout’s release, with lawmakers in Russia’s State Duma describing Bout’s detainment at the time as politically motivated.

Reports of the prisoner swap trickled out for weeks, indicating the Biden administration hoped to swap Bout for both Griner and former U.S. Marine Paul Whelan, who is also detained in Russia and was not released in Thursday’s deal. 

“Sadly, for totally illegitimate reasons, Russia is treating Paul’s case different than Brittney’s,” Biden said on Thursday. “And while we have not yet succeeded in securing Paul’s release, we are not giving up. We will never give up.”

Bout was born in 1967 in Tajikistan, then under the control of the Soviet Union.

He attended the Military Institute of Foreign Languages and served in the Soviet military, although accounts differ on the specifics of his service. 

He reportedly worked in Russian intelligence, and Bout has publicly touted his ability to speak multiple languages in interviews over the years.

Bout has publicly said he subsequently moved to the United Arab Emirates and began an air cargo operation.

In 1996, Bout registered cargo airline Air Cess in Liberia and began forming a network to ship weapons to regimes under international sanctions, according to a 2000 U.N. report.

A separate U.N. report indicates Bout maintained a network of more than 50 planes and tens of airline companies, many of which were involved in shipping illicit cargo. As one example, Bout flew 37 arms flights to Angolan rebel group UNITA, which was under U.N. sanctions at the time.

Bout has also been accused of arms deliveries to regimes in places like Liberia, Sierra Leone, the Democratic Republic of the Congo and Algeria.

In the Middle East, Bout has been accused of aiding the Taliban and al Qaeda, although Bout has denied those reports.

As international scrutiny grew over his operations, British foreign office minister Peter Hain in a 2000 speech to the House of Commons described Bout as a “merchant of death” and “chief sanctions-buster,” coining two nicknames that have gained significant recognition.

“Grubby deal,” Hain wrote on Twitter on Thursday.

Bout was ultimately arrested in March 2008 in Bangkok, Thailand, as part of a Drug Enforcement Agency international sting operation, court documents show.

Bout had agreed to sell the Revolutionary Armed Forces of Colombia (FARC) weapons for the guerilla group to use to protect their cocaine-trafficking business and attack U.S. interests in Colombia.

The FARC was designated a terrorist organization by the U.S., although Secretary of State Antony Blinken revoked the designation one year ago after the group formally dissolved and disarmed.

A U.S. jury returned an indictment against Bout one month after his arrest for participation in conspiracies to kill U.S. nationals, kill U.S. officers or employees, acquire, transfer and use anti-aircraft missiles as well as provide material support to a designated foreign terrorist organization.

A Thai judge granted Bout’s extradition, and he arrived in New York in November 2010, according to court documents.

A jury convicted Bout on all four counts one year later, and he was sentenced on March 12, 2012, to 25 years in prison.

Days before his sentencing, Russian lawmakers wrote to the judge overseeing Bout’s case, describing his incarceration as being conducted for “political motivation.”

“In business circles, among colleagues, friend and relatives, Victor Bout has been regarded for a long time as an honest, respectable, moral and kind-hearted person and as a law-abiding, responsible and trustworthy businessman,” they wrote. “Victor Bout has never been accused of crime within the territory of the Russian Federation. He is an exemplary family man.”

At the time of his release, Bout was housed in a medium-security federal prison near Marion, Ill.