The Pentagon is concerned that convicted Russian arms dealer Viktor Bout, the "Merchant of Death" who was freed Thursday in a prison swap for WNBA star Brittney Griner, could go back to illegally trafficking weapons, thereby fueling deadly conflicts around the world. 

"I think there is a concern that he would return to doing the same kind of work that he's done in the past, a senior Defense Department official said.

Bout was in the middle of serving a 25-year prison sentence in a U.S. prison for several offenses, including conspiring to kill Americans, when he was freed. Griner was arrested at Sheremetyevo Airport in Moscow on Feb. 17 after Russian authorities said she had vape cartridges with cannabis oil inside her luggage. 

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Convicted Russian arms dealer Viktor Bout walks past temporary cells ahead of a hearing at the Criminal Court in Bangkok on August 20, 2010. The Pentagon voiced concerns about Bout going back into arms dealing after being released in a prisoner exchange for Brittney Griner. (CHRISTOPHE ARCHAMBAULT/AFP via Getty Images)

On Aug. 4, she was given a nine-year sentence after pleading guilty, arguing that she had been prescribed cannabis for her pain and inadvertently packed it. Her sentence was upheld in October, and she was later transferred to a penal colony.

Bout, a former Soviet military officer known as the "Merchant of Death," spent years supplying weapons to dictators and to conflicts across the world, sometimes supplying both sides. 

"If I didn’t do it, someone else would," he told the New Yorker in 2012. 

He carried out his dealings with a fleet of cargo airplanes that transported arms and military equipment to various parts of the world, including Africa, South America, and the Middle East, according to a 2010 Justice Department indictment. 

Many of the weapons he sold fueled civil wars in Africa. Former Liberian President Charles Taylor is believed to have been a customer.

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WNBA star and two-time Olympic gold medalist Brittney Griner is escorted from a court room ater a hearing, in Khimki just outside Moscow, Russia, Aug. 4, 2022. On Thursday, she was freed in exchange for Viktor Bour, a convicted international arms dealer. (WHD Photo/Alexander Zemlianichenko, File)

In a statement, Sen. Bob Menendez, D-N.J., chairman of the Senate Foreign Relations Committee, said there is no equivalence "between the Brittney Griners of the world and people like Viktor Bout."

"Nothing could be further from the truth, and we cannot ignore that releasing Bout back into the world is a deeply disturbing decision," he said. "We must stop inviting dictatorial and rogue regimes to use Americans overseas as bargaining chips, and we must try to do better at encouraging American citizens against traveling to places like Russia where they are primary targets for this type of unlawful detention."

Bout was nabbed in 2008 in a sting operation at a luxury hotel in Bangkok, Thailand, where he met with Drug Enforcement Administration informants who were posing as officials with the Revolutionary Armed Forces of Colombia (FARC), which has been classified by US officials as a narco-terrorist group.

Prosecutors said that Bout was prepared to provide the group with $20 million worth of "a breathtaking arsenal of weapons — including hundreds of surface-to-air missiles, machine guns and sniper rifles — 10 million rounds of ammunition and five tons of plastic explosives."

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Should Bout return to arms trafficking, particularly in Africa, the U.S. would warn its allies of the potential dangers of going into business with someone like him. Russia is also currently engaged in its invasion of Ukraine. 

"If his network and if that were to come to fruition, then we would definitely share the challenges of what we think illicit weapons or illegal weapons could mean for their prosperity and their ability to have a stabilized government and security response," the defense official said.