corps vs militia

corps

noun
  • An organized group of people united by a common purpose. 

  • A battlefield formation composed of two or more divisions. 

militia

noun
  • An army of trained civilians, which may be an official reserve army, called upon in time of need, the entire able-bodied population of a state which may also be called upon, or a private force not under government control. 

  • Synonym of militsia: the national police force of certain countries (e.g. Belarus). 

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