China systematically crippled CIA operations, killing or imprisoning up to 20 sources.
China killed or imprisoned 18 to 20 CIA sources from 2010 to 2012, hobbling U.S. spying operations in a massive intelligence breach.
www.businessinsider.com/r-china-killed-cia-sources-hobbled-us-spying-from-2010-to-2012-nyt-2017-5