foot soldier vs man-of-war

foot soldier

noun
  • A soldier who fights on foot; an infantryman 

  • A rank and file member of an institution, or supporter of a cause. 

man-of-war

noun
  • A man whose occupation is fighting in wars; a soldier, a warrior. 

  • A powerful armed naval vessel, primarily one armed with cannon and propelled by sails; a warship. 

  • The Arctic skua (Stercorarius parasiticus). 

How often have the words foot soldier and man-of-war occurred in a corpus of books? (source: Google Ngram Viewer )