Letter to Secretary Gates Designating Him To Act as Secretary of Defense
Dear Mr. Secretary:
In the event of the absence of the Secretary of Defense during the next thirty days or until the appointment of a Deputy Secretary of Defense pursuant to law, you are, under the provisions of Part V of Executive Order 10820 dated May 18, 1959, designated to act as Secretary of Defense, and authorized and directed to perform the duties of that office, during his absence.
DWIGHT D. EISENHOWER
Note: The Honorable Thomas S. Gates, Secretary of the Navy, was subsequently appointed by the President as Deputy Secretary of Defense and assumed his new duties on June 8, 1959.
Dwight D. Eisenhower, Letter to Secretary Gates Designating Him To Act as Secretary of Defense Online by Gerhard Peters and John T. Woolley, The American Presidency Project https://www.presidency.ucsb.edu/node/234896