strife vs tug of war

strife

noun
  • Bitter conflict, sometimes violent. 

  • A trouble of any kind. 

  • Striving; earnest endeavor; hard work. 

  • Exertion or contention for superiority, either by physical or intellectual means. 

tug of war

noun
  • A dispute between two parties, particularly an entrenched, back-and-forth dispute. 

  • A game or competition in which two teams pull or tug on opposite ends of a rope trying to force the other team over the line which initially marked the middle between the two teams. 

How often have the words strife and tug of war occurred in a corpus of books? (source: Google Ngram Viewer )