Arsenal of Democracy vs arsenal of democracy

Arsenal of Democracy

arsenal of democracy

noun
  • The United States of America, as supplier of extensive materiel support to U.S. allies during World War II; or post-war U.S. as the manufacturer and possessor of the greatest quantity of advanced military weaponry in the world, in the service of defending democratic forms of government. 

How often have the words Arsenal of Democracy and arsenal of democracy occurred in a corpus of books? (source: Google Ngram Viewer )