armed struggle vs friction

armed struggle

noun
  • An irregular political conflict waged by an armed rebel group attempting to overthrow the prevailing regime or otherwise win political rights. 

friction

noun
  • Conflict, as between persons having dissimilar ideas or interests; clash. 

  • The rubbing of one object or surface against another. 

  • A force that resists the relative motion or tendency to such motion of two bodies in contact. 

  • (Second Sino-Japanese War) Conflict, as between the Communists and non-Hanjian Kuomintang forces. 

How often have the words armed struggle and friction occurred in a corpus of books? (source: Google Ngram Viewer )