fort vs supply depot

fort

noun
  • A fortified defensive structure stationed with troops. 

  • Any permanent army post. 

  • An outlying trading-station, as in British North America. 

  • A structure improvised from furniture, bedding, etc., for playing games. 

verb
  • To create a fort, fortifications, a strong point, or a redoubt. 

supply depot

noun
  • A facility utilized by armies to store battlefield supplies temporarily on or near the front lines until they can be distributed to army units. 

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