On a blistering day in the middle of the Iraqi summer, Najmaldin Karim, the provincial governor of Kirkuk, climbed in his armored car and went down to Republic Street, a small strip of fruit stands and shops in the heart of this dusty oil town north of Baghdad.

Give Kirkuk time, Karim says, and Republic Street will return to the way he remembers it as a boy: an oasis of tearooms and movie theaters where the melting pot of local ethnic groups mixed with ease.

A little over a year ago, Karim, 62, was a neurosurgeon with a thriving practice in suburban Washington, living with his wife in an expansive brick house in Silver Spring.

After 35 years in the United States, Karim, an American citizen, decided to return to Iraq after he saw that American forces and an entrenched local bureaucracy were making scant progress toward reconstruction. Unlike other Americans who rushed to help in Iraq and Afghanistan in the early days of combat, Karim is a new breed of returning exile who won the support of his countrymen on his own, without the support of the U.S. military — something that’s seen here as a plus.

He has come back to right the shambles of his home town at a time when Kirkuk’s future is as clouded with uncertainty as Iraq itself.

On this summer day, Karim could hardly walk a few paces outside, flanked by a security detail so large it overwhelmed the narrow street. Shopkeepers and customers stopped to stare. In a place where Islamic extremists have assassinated 10 police officers and politicians this year and, according to police, kidnapped 45 wealthy locals in the past year, the tension in the open air market was palpable.

The sunbaked city of 900,000, sitting atop a fifth of the country’s oil supply, has simmering ethnic tensions that go back decades.

The 4,500 U.S. troops who have helped keep the peace among the city’s three major ethnic groups — Kurds, Arabs and Turkmens — are on their way out. U.S. officials say Kirkuk will be watched closely in the coming months as a bellwether of the country’s fragile democracy. If Iraq descends into chaos after the Americans leave, some experts say, its fracture point may be Kirkuk.

‘We can’t be afraid’

Zozan Karim, Najmaldin’s wife of more than three decades, says her husband never asked her whether he should return to Iraq. He had been a well-known lobbyist for Kurdish causes on Capitol Hill for decades and had founded the Washington Kurdish Institute, so it was almost expected.

“He just showed me his ticket and went,” she recalled with a laugh. “I always knew he would go back. I knew it when I married him.”

She has stayed behind while their youngest son finishes up his studies at the University of Maryland.

Karim returned in 2010, winning a seat in parliament representing Kirkuk — where he grew up with 10 siblings, the son of a teacher. He was appointed governor this spring.

Several visits during the war “made me realize I could do more,” Karim said during a recent interview in his office in the provincial government building.

Karim spends his days navigating the competing interests of rival ethnic groups while trying to restore a city ravaged by eight years of war. He eats dinner alone in a heavily guarded compound ringed with concrete blast walls. He lives in the only house that was secure enough, a tan-and-salmon-colored villa that once belonged to Gen. Ali Hassan al-Majeed, a cousin of Saddam Hussein who became known as “Chemical Ali” for ordering poison-gas attacks on Kurdish civilians.

“We can’t be afraid,” Karim said. “We get threats every day, sometimes more than once an hour some days, from terrorists. . . . To do this job, you have to stand up to those people and not be afraid.”

As he spoke, Karim flipped a string of red worry beads, a relaxation practice common among his countrymen that he has adopted. Not long after he took office in April, a car bomb exploded two blocks away, injuring 13 people.

When Karim arrived in Kirkuk, residents had only four to six hours of electricity a day and water service was intermittent. Refugees squatted in abandoned buildings, as many as six families to a room.

In the past five months, he has helped negotiate a complicated deal that disconnected the city from Baghdad’s troubled electrical grid and linked it to Kurdistan’s, increasing electrical service to 18 hours a day. The city is building two new pumping stations for water and 700 housing units for refugees.

After the U.S. invasion in 2003, Kurds who had been expelled by Hussein and replaced by Arab families returned by the thousands, hoping to reclaim their lost homes. Disputes over land rights are common, and many are still homeless. Soldiers from all three ethnic groups help keep the peace — and sometimes end up in tense standoffs themselves.

Over it all hangs the central question: Should Kirkuk remain part of Iraq proper or be governed by the semiautonomous region of Kurdistan to its north? Plans for a census to determine who lives in Kirkuk and a referendum to decide its governance, promised by the Iraqi constitution, have stalled.

U.S. Gen. Ray Odierno, a former top commander in Iraq, has called the Kurdish-Arab conflict the chief threat to Iraq’s stability. And many Middle East scholars agree.

Joost Hiltermann, an Iraq analyst for the International Crisis Group, said that the Americans’ work setting up joint patrols and checkpoints in disputed areas such as Kirkuk has helped keep the peace between the central government in Baghdad and the Kurdistan Regional Government but that without their help, things could worsen.

“There is potential for these small provocations and clashes to escalate into a broader conflict, a potential that is only increased if the transition to a post-U.S. troop era is not carefully managed,” Hiltermann said.

Karim dismisses the oft-used descriptions of his home town as a “tinderbox” or a “powder keg” that could ignite at any moment. “There’s a danger,” he admitted. “But it’s not so explosive that the day they leave, everybody starts killing each other.”

He has reason to be optimistic. Despite assassinations, kidnappings and twin bomb attacks in May that killed 27, violence in Kirkuk has decreased this year. But there’s no doubt Karim wants U.S. troops to stay.

A promise of change

After his short trip to Republic Street, Karim climbed back in his armored car for a tour of the city’s construction projects, including a $25 million mall and hotel complex being built by an Austrian company. The car sped past low-slung concrete buildings and piles of rubble, date palms and scrub pines, impossibly clean yellow taxis and dust-caked sedans.

“Come back here in two years and Kirkuk is going to be a totally different city,” Karim promised.

If things stay peaceful?

“I think they will,” he said softly. His worry beads clicked.

Early the next day, near Karim’s office, a car bomb ripped through St. Ephraim Syrian Orthodox Church, reducing part of it to rubble. It was the city’s third church bombing in a month. A little while later, a booby-trapped motorcycle and another car bomb exploded in the southern part of the city; killing one bystander and injuring three.

Special correspondent Aziz Alwan in Baghdad and staff researcher Magda Jean-Louis in Washington contributed to this report.