[Sudan ousted a brutal dictator. His successor was his enforcer.]

For the protesters who have dared challenge the military rulers in the vast African nation of Sudan, it seemed a gloomy moment — yet another Arab uprising thwarted by autocracy, violence and repression. But Dr. Ali remains defiant, even hopeful.

“This is not the end of the revolution,” he said. “It’s just the beginning.”

Sudan drew the world’s attention a few months ago when thousands of protesters besieged the capital, fed up with economic hardships and the 30-year reign of President Omar Hassan al-Bashir.

Under intense pressure the military generals surrounding the president forced him to step down, started running the country themselves and promised change. But the heady optimism created by Mr. al-Bashir’s downfall gave way to new tensions, as the generals resisted protester demands for a swift transition to civilian rule. Then, with little warning, came the crackdown a week ago.

Despite Dr. Ali’s upbeat attitude, Sudan’s underground revolutionaries are arrayed against formidable forces, inside and outside the country.

[Read about how a power-sharing deal came about in July 2019.]

On Sunday they made a new bid to wrest control from the military junta with a general strike that paralyzed Khartoum and other major cities. Streets were largely deserted and shops shuttered. Protesters mounted barricades on suburban streets. The security forces killed at least three protesters, doctors said.