combat vs go to war

combat

verb
  • To fight; to struggle against. 

  • To fight (with); to struggle for victory (against). 

noun
  • A battle, a fight (often one in which weapons are used). 

  • a struggle for victory 

go to war

verb
  • To enter into an armed conflict. 

  • (of a person) To depart, typically from one's home, to join an army at war. 

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