How were some censored Chinese books preserved in Japan and Korea?

During the reign of the Qianlong emperor, the Qing dynasty implemented strict censorship policies, ordering the destruction of approximately 2,600 titles deemed seditious for containing anti-Manchu declarations or allusions.1

Despite these efforts to purge such works from China, several hundred of these censored books were preserved because copies happened to exist in Japanese or Korean libraries. These foreign collections served as a vital repository, allowing texts that were targeted for eradication by the imperial court to survive outside of the reach of the Qing dynasty's literary inquisition.1