officer list results from service under a temporary appointment or in a grade held by reason of assignment to a position has, when that appointment or assignment ends, the grade and position on the Space Force officer list that the officer would have held if the officer had not received that appointment or assignment. 20235. Competitive categories (a) Requirement To establish competitive categories for promotion Under regulations prescribed by the Secretary of Defense, the Secretary of the Air Force shall establish at least one competitive category for promotion for officers on the Space Force officer list. Each officer whose name appears on the Space Force officer list shall be carried in a competitive category of officers. Officers in the same competitive category shall compete among themselves for promotion. (b) Single competitive category for promotion to general officer grades The Secretary of the Air Force shall establish a single competitive category for all officers on the Space Force officer list who will be considered by a selection board convened under section 20211 of this title for promotion to the grade of brigadier general or major general. 20236. Numbers to be recommended for promotion (a) Promotion to grades below brigadier general (1) Before convening a selection board under section 20211 of this title to consider officers for recommendation for promotion to a grade below brigadier general and in any competitive category, the Secretary of the Air Force shall determine— (A) the number of positions needed to accomplish mission objectives which require officers of that competitive category in the grade to which the board will recommend officers for promotion