In a courtroom in Zharkent, Kazakhstan, in July 2018, a former kindergarten principal named Sayragul Sauytbay calmly described what Chinese officials continue to deny: a vast new gulag of “de-extremification training centers” has been created for Turkic Muslim inhabitants of Xinjiang, the Alaska-sized region in western China. Sauytbay, an ethnic Kazakh, had fled Xinjiang and