As the new prime minister of Haiti, a country with no president or Parliament, where gangs have destroyed dozens of police stations and killed thousands of people, Garry Conille has arguably one of the toughest jobs of any leader in the Western Hemisphere.

He has attended funerals for slain police officers and met with their widows. He fired the police chief — blaming him for failing to fight the gangs — and named a new one, and he ushered in a contingent of police officers from Kenya tasked with helping alleviate the violence. He spent last week knocking on doors in Washington with an urgent message:

“This is no time for Haiti fatigue.”

Mr. Conille, 58, a former longtime U.N. official who had lived outside Haiti for more than a decade, took over the helms of Haiti’s government five weeks ago amid one of the country’s worst crises in decades.

The position had become vacant after armed groups joined forces to attack prisons, hospitals and entire neighborhoods in an uprising so severe that the former prime minister, who was on an overseas trip, could not return to his own country.

Mr. Conille was chosen by a presidential transitional council that is helping to oversee the country.

A gynecologist by training, Mr. Conille now must restore order to Haiti in the hopes of organizing orderly and fair elections for president and Parliament. He is viewed as something of an outsider unstained by Haiti’s notoriously dirty politics and chronic corruption who was appointed with the blessing of the Biden administration and the international community.