ethnic cleansing vs mass destruction

ethnic cleansing

noun
  • The mass expulsion or killing of people belonging to one ethnic group by those of another. 

mass destruction

noun
  • Killing of large numbers of people. 

  • Used other than figuratively or idiomatically: see mass, destruction. 

How often have the words ethnic cleansing and mass destruction occurred in a corpus of books? (source: Google Ngram Viewer )