ISTANBUL — As a writer and magazine editor, Qurban Mamut promoted the culture and history of his people, the Uighurs, and that of other Turkic minority groups who live in far western China. He did so within the strict confines of censorship imposed by the Chinese authorities, who are ever wary of ethnic separatism and Islamic extremism among the predominantly Muslim peoples of the region.

It was a line that Mr. Mamut navigated successfully for 26 years, eventually rising to become editor in chief of the Communist Party-controlled magazine Xinjiang Civilization before retiring in 2011.

“My father is very smart; he knows what is the red line, and if you cross it you are taken to jail,” said his son, Bahram Sintash, who now lives in Virginia. “You work very close to the red line to teach people the culture. You have to be smart and careful with your words.”

Then last year, the red line moved. Suddenly, Mr. Mamut and more than a hundred other Uighur intellectuals who had successfully navigated the worlds of academia, art and journalism became the latest targets of a sweeping crackdown in the region of Xinjiang that has ensnared as many as one million Muslims in indoctrination camps.