battlefront vs theater of war

battlefront

noun
  • The region or line along which opposing armies engage in combat. 

  • The area in which opponents or opposing ideas meet. 

theater of war

noun
  • The area in which armed conflict takes place. 

  • A subject that is highly contentious; an area of conflict. 

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