call up vs enlist

call up

verb
  • To summon (someone) to report for military service. 

  • To select e.g. to a sports squad. 

  • To retrieve from personal or computer memory. 

  • To call on the telephone. 

noun
  • An order to report for military service. 

enlist

verb
  • To voluntarily join a cause or organization, especially military service. 

  • To recruit the aid or membership of others. 

  • To enter on a list; to enroll; to register. 

  • To secure; to obtain. 

noun
  • One who is enlisted, usually in a military service. 

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