demobilize vs impel

demobilize

verb
  • To disband troops, or remove them from a war footing. 

  • To release someone from military duty, especially after a war. 

impel

verb
  • To urge a person; to press on; to incite to action or motion via intrinsic motivation. 

  • To drive forward; to propel an object, to provide an impetus for motion or action. 

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