William R. Brownfield, assistant secretary of state in charge of the Bureau of International Narcotics and Law Enforcement Affairs, testifies during a Senate Foreign Relations Committee hearing last month. (Tom Williams/CQ Roll Call/Associated Press)

To the extent that diplomacy is a kind of performance art, few U.S. Foreign Service officers have practiced it over the past several decades with as much flair as William R. Brownfield.

With his deadpan humor, theatrical delivery and a fondness for red suspenders, Brownfield is among the more distinctive personalities in a U.S. diplomatic corps typically known for caution and reticence.

In Latin America, where he spent much of his career, Brownfield has been a popular and sometimes notorious figure, as an irritant to the late Venezuelan president Hugo Chávez as well as one of the chief architects of the $10 billion Plan Colombia security aid package that helped end the country's half-century civil conflict.

The Trump administration's talk of ramping up the drug war made Brownfield a leading candidate for the job of assistant secretary for Western Hemisphere affairs, the top U.S. diplomat in the Americas. Instead, he will retire this month after nearly 40 years in the Foreign Service, adding to the list of seasoned U.S. diplomats leaving the government

Secretary of State Rex Tillerson has moved slowly to fill key high-level posts, and critics say multiple departures are further hollowing out the country's diplomatic corps. Each of the State Department's regional assistant secretary jobs — critical to crafting and implementing U.S. foreign policy — is held by someone in an acting role. 

Brownfield is one of only three remaining diplomats with the title of career ambassador, the highest distinction in the Foreign Service. His wife, Kristie Kenney, a three-time ambassador, also held that rank, but she retired this year after she was demoted from her job as State Department counselor and stripped of her staff.

Ever the loyal soldier, Brownfield openly betrays no hard feelings toward President Trump or Tillerson. Brownfield points out that at 65 he has reached the age when Foreign Service officers are expected to retire.

His exit undoubtedly leaves a hole at the heart of U.S. counternarcotics efforts abroad, particularly when drug addiction and overdose deaths in the United States are a full-blown crisis.

"If only I had timed my departure to be five years ago," he said in an interview last week at the State Department, where he leads the agency's Bureau of International Narcotics and Law Enforcement Affairs. 

"We were justifiably proud of what we'd accomplished in 2012," he said. "That's not the case now."

In 2012, U.S. cocaine consumption and the size of the illegal coca crop in Colombia were near a low point, and much of the praise in Washington went to those responsible for designing and implementing Plan Colombia. Among them was Brownfield, who served as U.S. ambassador in Bogota from 2007 to 2010.

Since then, Colombian farmers have been stuffing their fields with record amounts of illegal coca, coerced by trafficking groups or to qualify for cash handouts offered under crop-substitution programs linked to the government's peace deal with leftist guerrillas. Colombia's cocaine production ballooned to 710 metric tons last year, according to U.S. estimates, up from 235 metric tons in 2013.

Brownfield also blames Colombia's 2015 decision to ban aerial spraying of illegal coca. U.S.-funded crop dusters were a pillar of Plan Colombia, but the herbicides are suspected of causing cancer.

The cocaine surge is fraying the U.S.-Colombia partnership that Brownfield worked so long to help build. Last week, Trump took the extraordinary step of threatening to blacklist Colombia as a nation that has "failed demonstrably" to meet its commitments as a partner in the drug war. 

The mere idea of such a designation was unthinkable just a few years ago, and it would put Washington's closest ally in Latin America in the company of Venezuela and Bolivia, nations whose relations with the United States are adversarial. 

"For the past year, in our private discussions, both Colombia and the United States have emphasized the importance of drugs not becoming a negative element in the bilateral relationship between two friends," Brownfield said. The president's statement, he added, "reemphasizes that importance."

Colombia's drug-production relapse has clearly weighed on Brownfield, and he said whoever succeeds him will have to cope with both a flood of methamphetamine and opioid trafficking from Mexico as well as the latest new surge of South American cocaine.

Brownfield nonetheless insists that Latin America has changed for the better since he joined the Foreign Service, with an expanding middle class and democratic governance the norm. "When I started, there were only four nonmilitary governments in the region," he said. "I can say emphatically it's a far better region today."

Brownfield grew up in Brownfield, Tex., a ranching and cotton-farming town founded by his ancestors southwest of Lubbock. When his great-grandfather divided up his 64,000-acre ranch among five heirs, Brownfield's grandfather was the only one whose land wasn't sitting on commercial quantities of oil and gas. "Today I have a lot of happy cousins," he said.

Brownfield's father joined the U.S. Army in 1939, retiring as a brigadier general nearly 30 years later. His brother was also a career military officer.

Brownfield took the Foreign Service exam as a law student at the University of Texas, mostly he said, "because it was free." 

He asked to be sent to the Middle East after Foreign Service school but was assigned to Georgetown, Guyana. It was just after the Jonestown massacre, and as a junior vice consul, Brownfield would have helped with the job of repatriating the remains of hundreds of the Rev. Jim Jones's followers.

Pleading for another posting, he was offered Maracaibo, the capital of Venezuela's oil industry. He immediately accepted, assuming it was somewhere in North Africa. "I had to rush down to the library to find it on a map," he said.

Brownfield returned to Venezuela as U.S. ambassador from 2004 to 2007 and made a point of visiting pro-Chávez neighborhoods while promoting "baseball diplomacy" between the two nations. Chávez cast him as a meddlesome imperialist, and Brownfield said he woke up in a hotel once and learned from CNN that Chávez had threatened the night before to kick him out of the country. It wouldn't be the last time. 

Brownfield calls those years his most miserable in the Foreign Service, when he once had to outrun a stone-throwing mob. Chávez publicly celebrated Brownfields's departure with chants of "Oooh Ahhh Brownfield is Leaving!" At the end of his tour, Brownfield showed up at an embassy party wearing a T-shirt with the phrase printed on it.

He still keeps a large Chávez bobblehead doll on a bookshelf. On one side of the doll is a statue of a rifle-toting Colombian soldier. On the other, an Arizona ranger. They've got him surrounded.

"Bill's an original," said Bernard Aronson, the former U.S. special envoy to the Colombia peace talks, who was Brownfield's boss in the early 1990s. "He can give a speech that a stand-up comedian could give, but buried behind his wry humor and jokes, there's substance in it. And I've never seen anyone put him in a partisan bind, which is a rare thing. It's a real loss for State," he said.

Colleagues say Brownfield has been particularly skilled at using humor to set up a tough message. 

"He comes off as this odd guy who is irreverent and sarcastic, but he's really direct in dealing with people," said Roberta Jacobson, the U.S. ambassador to Mexico. "There are very few people I've learned as much from."