Months of negotiations between Washington and Moscow have led to a high-profile prisoner swap, a rare moment of agreement between the two countries which are at odds on several fronts, primarily the Ukraine war.
Moscow had been calling for his release since a US court imprisoned him on terrorism charges in 2011.
In both their home countries, the prisoners’ lengthy jail sentences were decried as politically motivated.
A vegetarian speaking six languages, Bout was born in Dushanbe, Tajikistan, when it was a part of the Soviet Union.
He served the military in overseas deployments in Africa.
In the 1990s, he launched a private airline company and acquired a fleet of military aircraft, which he used to ship cargo, including humanitarian aid as well as weapons, to war zones.
His clients included the Russian and US governments, as well as Liberian war criminal Charles Taylor. Bout’s career was the partial inspiration for the 2005 film Lord of War, starring Nicolas Cage.
In 2008, Bout was arrested in Bangkok after agreeing to sell surface-to-air missiles to who he thought were Colombian FARC rebels, but was actually a sting by the US Drug Enforcement Administration (DEA).
Until last year, the FARC was considered a terrorist group by the US government.
He was convicted three years later for conspiring to kill Americans and sentenced to 25 years.
Bout loudly protested, claiming to be innocent. He alleged he had been set up and that the case against him was politically motivated.
He has denied any connections to Russian intelligence or organised crime, describing himself as a legitimate businessman.
Moscow echoed his claims, and Russian officials repeatedly raised concerns about the conditions he was kept in.
The judge in Bout’s case has said he was manipulated to a certain extent by US agents, and had she not been bound by the rules on minimum sentencing, in Bout’s case 25 years, she would have given him a shorter spell.
“We tried him, we convicted him, we gave him a very long sentence,” retired US District Judge Shira Scheindlin, who led the sentencing in 2012, told the Reuters news agency earlier this year, as she argued for a swap with Griner. “But now the situation has changed and this is a trade we should make.”
Scheindlin said she believed Bout would not commit the offence again since he had probably lost his place in the arms trafficking network during his imprisonment.
Mark Galeotti, an expert on Russian security affairs, told Al Jazeera via email: “There was considerable political pressure on the White House to get Griner out – and at the same time, the Russians wanted Bout released because he was probably an intelligence asset and they do still hold to the old, KGB-era promise that one way or the other, they get their people home.
“It is not so much for Bout’s sake as to reassure other agents in the field that Moscow would not forget them.”
Griner, who played for a Russian team part-time, was arrested at Moscow’s Sheremetyevo airport in February after vape cartridges with less than a gram of cannabis oil were found in her luggage.
She was then sentenced to nine years, which those familiar with Russian drug laws considered exceedingly harsh.
“Her sentence was [entirely] politically motivated,” Russian human rights lawyer Arseny Levinson told Al Jazeera. “She should not have been sentenced to a real prison term at all. Moreover, such a severe punishment should not have been imposed, it was motivated solely by raising the stakes in the exchange, making a mockery out of the hostage.”
While there is no indication Griner was framed, it appears that her unusually long sentence may have been a way to put pressure on Washington.
“Russia has always maintained that he [Bout] was wrongfully imprisoned by the United States,” Kimberly St Julian-Varnon, an American historian of Russian and Soviet history, told Al Jazeera.
“He was important to the United States because of his worth to Russia. I think the Biden administration was willing to swap him because of the public pressure on the administration to secure Griner’s release, and because he was the highest-profile Russian America had in custody.
“Griner was the highest-profile American Russia had. I think the Russians were using Brittney Griner as a pawn. The proof is in the outcome – they secured the release of a highly dangerous arms dealer that they have wanted since 2011.”
But is the swap a sign of warming ties? It is unlikely.
“It is probably wrong to draw any hypothetical conclusions that this could be a step towards overcoming the crisis that we currently have in bilateral relations,” Kremlin spokesman Dmitry Peskov told Russia’s Izvestia newspaper on Friday.
US conservatives bemoan swap as pro-Kremlin Russians rejoice
The exchange was the second major prisoner swap between Moscow and Washington since the Russian invasion of Ukraine began in February, plummeting already poor relations between the two powers.
In April, American citizen Trevor Reed was freed from his nine-year term for assaulting a police officer in exchange for Konstantin Yaroshenko, a Russian pilot convicted of cocaine smuggling.
Like Bout, Yaroshenko was caught in a DEA sting which raised questions about the agency’s overreach.
Another high-profile American prisoner, former marine Paul Whelan, remains in Russian custody, two years into a 16-year penalty for spying.
In the US, the Bout-Griner deal has been criticised by conservatives for failing to rescue Whelan and receiving Griner instead, who is seen as unpatriotic for raising issues of racial injustice.
“What a ‘stupid’ and unpatriotic embarrassment for the USA!!!” former President Donald Trump wrote on social media.
Meanwhile, campaigners called on the White House to free those imprisoned for similar charges in the US.
Although marijuana is legal in 21 US states, some prisoners are languishing on life sentences over small amounts of the drug.
“Brittney Griner is free!” said neuroscientist and reformer Dr Carl Hart. “Now let’s free all drug war political prisoners.”
In Russia, the swap was welcomed by pro-Kremlin figures, who said the deal was a victory for Moscow.
Margarita Simonyan, RT editor, told her 500,000 Telegram subscribers that “we will win” since the swap prioritised Griner, who she offensively described as a “drug-addicted black lesbian who suffered for vaping hashish”, over Whelan, a “hero spy”.
Russian legal expert Ivan Solovyov told RT that the American justice system is able to “seize and judge” Russians with impunity, and that “all legal and human arguments were shattered by the unwillingness of the Americans to meet us half-way”.
According to him, it had “seemed that an insurmountable wall of geopolitical confrontation” had blocked the exchange for a while, until in the end, “politics and diplomacy, together with common sense, prevailed over the power of the American prison”.
Politician and journalist Yevgeny Popov told his 35,500 Telegram subscribers that “everyone will forget about Griner tomorrow” while “Bout’s life is only beginning” after posting pictures purporting to show Bout on a plane.