fortification vs supply depot

fortification

noun
  • That which fortifies; especially, a work or works erected to defend a place against attack; a fortified place; a fortress; a fort; a castle. 

  • A jagged pattern sometimes seen during an attack of migraine. 

  • The act of fortifying; the art or science of fortifying places to strengthen defence against an enemy. 

  • An increase in effectiveness, as by adding ingredients. 

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 fortification and supply depot occurred in a corpus of books? (source: Google Ngram Viewer )