(a) When a member of the armed forces of the state or the Governor’s military staff, whose service has been honorable, has served ten years, he or she may, if he or she makes a timely application to the Adjutant General through the chain of command prior to such member’s retirement date, be retired from active service and placed upon the retired list. Such retirement shall be in the highest grade in which he or she has served. When such service equals or exceeds twenty years, he or she may, upon his or her application to the Adjutant General, through the chain of command prior to such member’s retirement date, be commissioned at or promoted to the next higher grade than the highest grade at which he or she may have held at any time, either in the armed forces of the state or the Governor’s military staff or the armed forces of the United States, which higher grade shall not be above the grade of a brigadier general or sergeant major, and shall thereafter be placed upon the retired list with such grade. Members may only receive the retirement promotion provided under this section one time. In determining such term of service of twenty years, there may be added to any term of not less than ten years’ service in the armed forces of the state or the Governor’s military staff the term of service with the armed forces of the United States, either active, inactive or reserve. Retirement shall be obligatory for all members reaching the age of sixty-four years or as required for members of the National Guard and naval militia by laws and regulations pertaining thereto.

(b) A retired member of the armed forces of the state or the Governor’s military staff, whose service was honorable, who served thirty or more years and who did not apply for a retirement promotion prior to retirement, may apply directly to the Adjutant General to be commissioned at or promoted to the next higher grade than the highest grade at which he or she may have held at any time, either in the armed forces of the state or the Governor’s military staff or the armed forces of the United States, which higher grade shall not be above the grade of a brigadier general or sergeant major.