Children saw their parents taken away, students wondered who would pay their tuition and crops could not be planted or harvested for lack of manpower, the reports noted. Yet officials were directed to tell people who complained to be grateful for the Communist Party’s help and stay quiet.

The leaked papers offer a striking picture of how the hidden machinery of the Chinese state carried out the country’s most far-reaching internment campaign since the Mao era. The key disclosures in the documents include:

• President Xi Jinping, the party chief, laid the groundwork for the crackdown in a series of speeches delivered in private to officials during and after a visit to Xinjiang in April 2014, just weeks after Uighur militants stabbed more than 150 people at a train station, killing 31. Mr. Xi called for an all-out “struggle against terrorism, infiltration and separatism” using the “organs of dictatorship,” and showing “absolutely no mercy.”…

• The crackdown encountered doubts and resistance from local officials who feared it would exacerbate ethnic tensions and stifle economic growth. Mr. Chen responded by purging officials suspected of standing in his way, including one county leader who was jailed after quietly releasing thousands of inmates from the camps.