Temporary appointment provisions of Title 10 pertain to appointment in grades O-9 and O-10, wartime appointments, and appointment in grades O-3 through O-6 for officers in critical skills. While a similar authority was previously available to the Department of the Navy, the 2019 National Defense Authorization Act established the authority for all services.
10 U.S. Code § 601: Appointment of officers in grade O-9 or O-10 is made by the President with advice and consent of the Senate and is held for the duration of assignment to designated positions or pending reassignment to another such position.
10 U.S. Code § 603: During a period of war or national emergency, the President alone may appoint any qualified person to any grades below O-9.
10 U.S. Code § 605: Officers in grade O-2 through O-5 may be temporarily appointed by the President, with the advice and consent of the Senate, to the next higher grade if serving in a position in that grade in a skill with a critical shortage as determined by the Service Secretary. The officer must be recommended for this appointment by a board of officers convened for that purpose. The appointment is terminated when the officer leaves the position. This section also sets limits by grade and military service on the number of positions that can be designated for these appointments.
As of this writing, DoD instructions have not been modified to specifically address temporary promotions.
Military Service Policies
Military policies are expected to generally implement and amplify statutory requirements and DoD policy.