DEA agent Lou Milione and his team apprehended one of the world's most dangerous arms dealers, Viktor Bout. (Jahi Chikwendiu/WASHINGTON POST)

The DEA agents sat day after day in their smoke-filled command post in a Bucharest police station, checking their phones and e-mails for confirmation that one of the world’s most notorious arms dealers was coming.

Their sting was an elaborate one, a ruse involving a multimillion-dollar weapons deal between their informants posing as rebels in Colombia and Viktor Bout, a legendary arms trafficker known as “The Merchant of Death.”

But when Bout failed to show in Romania after two agonizing weeks of waiting, the agents decided to bow out for the moment, fearful of looking over-eager. They let Bout know they still wanted to meet him someplace else, and soon — although there was a risk he would slip away.

“If we were real, we would say we have other stuff to do,” said Lou Milione, the Drug Enforcement Administration agent who oversaw the high-stakes sting. “We just wouldn’t continue to wait. We were confident he would stay interested, but there is always that risk something would happen and he wouldn’t keep his interest.”

Within a few weeks, Bout was flying to Thailand to meet with the agents’ undercover informants in a posh hotel conference room. After Bout finalized a deal for guns, grenades, mortars and surface-to-air missiles that he knew would be used against Americans stationed in Colombia, authorities pounced.

DEA agents William Brown, left, Lou Milione and their team apprehended the one of the world's most dangerous arms dealers. The group is a finalist for the The Samuel J. Heyman Service to America Medals (Sammies), which pay tribute to the U.S. federal workforce, highlighting those who have made significant contributions to the country. (Jahi Chikwendiu/THE WASHINGTON POST)

Bout was arrested in March 2008 on federal charges, and he was eventually extradited to face trial in a federal courtroom in New York. Convicted in 2011 of four charges, including conspiring to kill Americans and providing material support to a designated terrorist organization, the Russian was sentenced in April to 25 years in prison.

For leading the international investigation, Milione is one of four finalists in the Justice and Law Enforcement category of the Samuel J. Heyman Service to America Medal for outstanding public service by federal employees. Nine of 33 total finalists will be awarded medals next Thursday.

Milione is quick to point out that the operation was a team effort involving two lead agents, William “Wim” Brown and Robert Zachariasiewicz; prosecutors in the U.S. Attorney’s Office for the Southern District of New York; as well as many other domestic and foreign law enforcement officials in countries stretching from Romania to Thailand.

The investigation would garner publicity across the globe, including stories in the New Yorker and on the TV news show “60 Minutes.”

“This is an international impact case,” said DEA agent Derek Maltz, who leads the agency’s Special Operations Division and supervises Milione. “You have one of the largest arms traffickers in the world moving weapons to extremists in different countries. He has been doing this for years. Books have been written and movies have been made about this man. . . . These guys did a phenomenal job to capture him and prosecute him.”

That Milione was the one who spearheaded the investigation would surprise those who knew him in the late 1980s. That was when the future agent was trying to make it big as an actor onstage and in television in New York. But after seven years of landing parts off-Broadway and in soap operas, Milione decided to pursue another lifelong dream: joining the DEA.

Milione — the son of a well-known conservative scholar, the late E. Victor Milione — grew up outside of Philadelphia listening to a relative who worked as a DEA agent tell stories about his job. He decided it would be a fun and challenging career. He obtained a law degree from Rutgers School of Law in Camden to help his chances of getting hired.

He became an agent in 1997 and was assigned to the DEA’s New York office, where he discovered the job was not all flash.

“There was lots of waiting,” he said, “on stakeouts and listening to wiretaps. Lots of work to build the complex cases. It wasn’t just rushing out to arrest guys and working undercover.”

Milione, whose wire-rimmed glasses make him look more like a corporate lawyer than a globe-trotting drug investigator, oversees two squads of agents out of his barren and nondescript office in Northern Virginia. His units investigate international drug traffickers and narco terrorists, a job that has many challenges, not least of which is trying to capture the targets in far-flung countries that are not always on good terms with the United States.

In 2007, the DEA arrested a notorious Syrian arms trafficker by constructing a sting involving informants posing as representatives of the Revolutionary Armed Forces of Colombia (FARC), a rebel group that has been at war with the Colombian government for decades and has been designated as a foreign terrorist organization by the U.S. government. FARC also happens to be responsible for supplying more than half of the world’s cocaine, according to the DEA.

Later that year, Milione’s team decided to attempt a similar operation targeting Bout, a man who had long been on the DEA’s radar for supplying weapons to drug traffickers. Bout was more than just an arms dealer. He had a larger-than-life reputation fueled by profiles in books and newspapers. Nicolas Cage played a character based on him in the 2005 film “Lord of War.” Over the years, Bout had been sanctioned by both the U.S. government and the United Nations, prosecutors wrote in court papers, because his “ability to transport all manner of weapons to conflict zones in Africa was so destructive and destabilizing.”

Milione and his agents knew the odds were against them. The agents were told by more than one U.S. intelligence official that their pursuit was hopeless: They would never be able to lure Bout to a country where he might be captured and eventually extradited to the United States.

Even so, they relied on a tried-and-true investigative technique: targeting a middleman, Andrew Smulian, a South African associate of Bout’s. The agents enlisted two informants who pretended to work for FARC and a third who knew Smulian as part of a deal the middleman might take to Bout.

The first meeting took place in January 2008 at a tiki bar in Curacao, a Dutch island in the Caribbean. From a safe distance and dressed casually in shorts and T-shirts, Milione, Brown and Zachariasiewicz munched on sandwiches, sipped colas and kept an eye on the players as they discussed a potential deal involving AK-47s, sniper rifles and missiles. It was a busy few days in Curacao — in an effort to save U.S. taxpayers money, the agents were running a parallel and unrelated undercover operation out of the same hotel.

At first, Smulian was cagey about his source of weapons. But within weeks, Smulian pulled aside one of the informants, according to court papers, and said: “I’ll give you the name of my friend so that you know, but this is just between you and me. It’s Viktor Bout. He’s named the ‘Merchant of Death.’ ”

Agents were now sure they were on the right path, and their informants invited Smulian and Bout to Bucharest to consummate the transaction. The DEA selected the spot because Romanian authorities were sympathetic to U.S. law enforcement efforts.

Even after Bout’s no show, it was clear he still wanted to make a deal. Once inside the Bangkok hotel, Bout negotiated around a long, polished wood conference table with Smulian and the informants, who made sure to explain how they were going to use some of the weapons — to kill Americans aiding Colombian authorities. The surface-to-air missiles would be aimed at helicopters flown by U.S. pilots, they told Bout.

“We have a policy,” Bout replied, “gringos are enemies.”

After Thai police raided the conference room and arrested Bout, Milione and his two agents finally got a chance to sit face-to-face with their quarry. “The Merchant of Death” did not seem like a person worthy of Cage’s “Lord of War” character, Yuri Orlov. His hands cuffed in his lap, the arms dealer sat slouched in a chair, his large belly nearly bursting from a bright orange shirt. He simply shrugged when the agents explained the evidence against him, including the tape recordings of their meetings.

“If everything is recorded, then you have everything,” said Bout, according to the agents. “You have all the cards on the table.”