With the recent news that Secretary of Defense Jim Mattis will be vacating his position sooner than originally stated in his resignation letter, Deputy Secretary of Defense Patrick M. Shanahan will be stepping into the Acting SECDEF role on January 1, 2019.  President Trump will now be actively engaged in finding a full-time permanent replacement.  Shanahan, interestingly, came to the position of Deputy SECDEF under Mattis from the American multinational aerospace defense corporation The Boeing Company, and has no prior military or government service.

The current and growing outcry regarding that last detail is as interesting as the fact itself.  Given that the Secretary of Defense is, according to Title 10 of the United States Code (which empowers the position), “the principal assistant to the President in all matters relating to the Department of Defense,” it is generally assumed that the SECDEF comes from a military background.  And this assumption is incorrect.

Including incoming Acting Secretary of Defense Shanahan, the United States has had 29 Secretaries of Defense since the establishment of the office in 1947.  This number includes 26 actual Secretaries, and three Acting Secretaries.  This number also includes Donald Rumsfeld, who served as both the 13th and 21st SECDEF (under Presidents Gerald Ford and George W. Bush, respectively), twice.

The reason both the lack of Shanahan’s military service and the outcry over that lack are interesting, is due to the fact that 9 of the total 29 serving Secretaries of Defense lack[ed] prior military service.  That’s essentially one-third of all the SECDEFs.  Shanahan will be the ninth.