combat vs let go

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 

let go

verb
  • To emotionally disengage or to distract oneself from a situation. 

  • To dismiss from employment. 

  • To release from one's grasp; to go from a state of holding on to a state of no longer holding on. 

  • To ignore (a comment, etc.). 

  • To fail to maintain a standard of appearance, behavior, or performance. 

  • Used other than figuratively or idiomatically: see let, go. 

  • To gain weight 

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