A New York jury found a Russian arms dealer, dubbed "the merchant of death," guilty of conspiring to sell a huge arsenal to US-designated terrorists, in a case that has angered Moscow.
Viktor Bout, 44, who was extradited from Thailand to the United States in 2010, was found guilty on all four counts including conspiring to kill US service personnel and to sell anti-aircraft weapons.
Federal Judge Shira Scheindlin set sentencing for February 8. Bout faces a minimum of 25 years and possibly up to life in prison.
"Today, one of the world's most prolific arms dealers is being held accountable for his sordid past," US Attorney General Eric Holder said in a statement.
The lead federal prosecutor for Manhattan, US Attorney Preet Bharara, said that "with today's swift verdict, justice has been done and a very dangerous man will be behind bars."
Bout's lawyer, Albert Dayan, immediately promised an appeal.
"It's definitely not the end of the process. We will appeal," Dayan told reporters. "We believe this is not the end. We have a chance."
Bout, dressed in a grey suit with a white shirt, looked despondent as he listened to the jury forewoman read out the verdict reached after fewer than eight hours of deliberations over two days.
He briefly hugged Dayan after the verdict and was led back to a detention center. His wife Alla and their teenaged daughter -- present through most of the trial -- were absent from the 15th-floor courtroom, which was packed with journalists and law enforcement agents.
Later, a distraught Alla Bout told AFP that her husband was the victim of political machinations.
"I don't think this was about justice. I would call this American nationalism," she said, fighting back tears.
But rights groups celebrated the downfall of a man alleged to have poured weapons into some of the world's bloodiest conflicts.
"It is a good day when the world’s most notorious arms trafficker is put out of business and off the market for good," said Oistein Thorsen, a campaigner with Oxfam International.
"However, it is tragic that because we have no global treaty regulating the activities of arms dealers, many other unscrupulous dealers and brokers will continue to operate."
The trial was the culmination of a sophisticated US sting operation to corner Bout, a veteran of a shady international air freight business that specialized in African conflict zones.
US informants posing as high-ranking members of Colombia's FARC guerrilla group, an underground leftist force that Washington considers a terrorist organization, told Bout at a 2008 meeting in Bangkok that they wanted to buy weapons.
Among the weapons requested were hundreds of Russian anti-aircraft missiles that the fake FARC representatives said would be used to shoot down US pilots aiding the Colombian military.
In the secretly taped conversations in Thailand, Bout told the fake FARC members that he could supply the weapons.
His lawyer had tried to argue in court that the Russian had in reality quit the arms trade and was merely playing a charade to further his real goal, which was to sell two unwanted cargo planes.
Bout was arrested at the 2008 meeting with the US agents, then extradited from Thailand to the United States after a bitter legal battle.
The mustachioed former Soviet military officer is alleged to have been the biggest private black market arms dealer in the post-Cold War period. He always denied this, saying he worked exclusively as a private air transporter -- though sometimes carrying legal shipments of arms -- and lived openly in Moscow.
Bout's more extended resume allegedly includes pouring weapons into wars in Afghanistan, Angola, the Democratic Republic of the Congo, Liberia, Rwanda, Sierra Leone and Sudan.
The movie "Lord of War," starring Hollywood actor Nicholas Cage, was inspired by Bout's life.
The chief US Drug Enforcement Administration agent who organized the Thailand sting branded Bout "one of the most dangerous men on the face of the Earth."
Arms expert and longtime Bout critic Kathi Lynn Austin said the verdict "closes the book on one of the most prolific enablers of war, mass atrocities and terrorism in the post-Cold War era."
"We should all be grateful that the world is safer now that the man who armed the hot spots of the globe is behind bars," she said in a statement.
Russians were outraged by Bout's arrest and extradition. There is also concern in Russia over the health of Bout, who has lost considerable weight since his arrest in Thailand.
Alla Bout said she thought her husband's only chance of ever leaving US prison would be through intervention "at a state level -- a government level."
Alexander Otchaynov, vice consul for Russia in New York, would not comment on the verdict. "Commentaries on such things will come later," he told reporters.