(a)
Notwithstanding any other provision of this title, whenever the Secretary determines that it is necessary to reduce the number of Reserve officers in an active status in any grade to provide a steady flow of promotion, or that there is an excessive number of Reserve officers in an active status in any grade, the Secretary may appoint and convene a retention board to consider all of the Reserve officers in that grade in an active status who have 18 years or more of service for retirement, except those officers who—
(1)
are on extended active duty;
(2)
are on a list of selectees for promotion;
(3)
will complete 30 years total commissioned service by June 30th following the date that the retention board is convened; or
(4)
have reached age 59 by the date on which the retention board is convened.
The retention board shall select and recommend a specified number of the officers under consideration for retention in an active status.