Former Soviet air force pilot Viktor Bout, who was swapped for US basketball star Brittney Griner today, fuelled some of the world's bloodiest conflicts by trafficking weapons across several continents.

In a career spanning two decades, and which stopped when he was sentenced to 25 years in a US prison in 2012, the 55-year-old Russian allegedly stoked violence from Sierra Leone to Afghanistan by bartering deals for planes and guns.

The mustachioed Bout, who is thought to speak six languages, travelled under various false names including "Boris" and "Vadim Markovich Aminov".

His notoriety inspired the Hollywood film "Lord of War", starring Nicolas Cage, in which the anti-hero escaped justice.

Expectations of a prisoner swap grew in recent months, after Russian leader Vladimir Putin and US President Joe Biden discussed his fate during a summit in Geneva in 2021.

CIA Director William Burns met with Sergei Naryshkin, head of Russia's SVR intelligence service, to discuss the swap involving Bout in Ankara last month, in what appeared to be the highest-level talks between Moscow and Washington since Russia sent troops to Ukraine in February.

Sting operation

Despite sanctions from the United States and United Nations, Bout had been trading weapons until he was caught in a sting operation in 2008.

The Russian was arrested at the five-star Sofitel hotel in Bangkok while negotiating with US agents posing as guerrillas from the Revolutionary Armed Forces of Colombia (FARC).

Viktor Bout's wife Alla Bout following her husband's extradition from Thailand in 2010

His appearances at court in Thailand, wearing a bullet-proof vest and shackles while flanked by armed police commandos, and the often tearful responses of his wife, Alla Bout, added to the drama of the case.

After a two-year legal battle, a Thai appeals court ruled in 2010 that he could be extradited to the United States, which accused him of running a "massive weapons-trafficking business" and terrorism.

Bout finally stood trial in the United States after he was flown out of Bangkok on a US government jet shortly after the Thai cabinet approved his extradition.

In 2012, a US judge sentenced Bout to 25 years in prison for conspiring to sell a massive arsenal to anti-American guerrillas in Colombia.

Bout maintained his innocence from the day he was picked up in the Thai capital after allegedly agreeing to supply surface-to-air missiles in a series of covert meetings that also took him to Denmark and Romania.

US prosecutors claim he agreed to the sale with the understanding that the weapons were to be used to attack United States helicopters.

Viktor Bout arriving at Westchester County Airport in 2010

'Unique creature'

Former British foreign office minister Peter Hain dubbed him the "Merchant of Death", while Amnesty International has alleged that at one time he operated a fleet of more than 50 planes ferrying weapons around Africa.

Prosecutors in the United States said the arms he sold or brokered fuelled conflicts and supported regimes in Afghanistan, Angola, the Democratic Republic of the Congo, Liberia, Rwanda, Sierra Leone and Sudan.

But Bout maintains that he has always run a legitimate air cargo business, and rejected claims of involvement with Al-Qaeda.

His detention enraged Russia, which called attempts at extradition politically motivated.

Born in Tajikistan's capital Dushanbe in 1967 when it was still under Soviet rule, Bout studied languages - including English, French and Portuguese - at Moscow's military institute for foreign languages before joining the air force.

Journalist Douglas Farah, who co-authored a book on Bout, has called him "a unique creature" born of the end of Communism and the rise of unbridled capitalism in the early 1990s.

He has repeatedly denied suggestions that he was a former KGB agent and that he bought weaponry, aircraft and helicopters at throwaway rates at the fall of the Soviet Union to supply to conflict zones.