((a)) There is an Assistant Commandant of the Marine Corps, appointed by the President, by and with the advice and consent of the Senate, from officers on the active-duty list of the Marine Corps not restricted in the performance of duty.

((b)) The Assistant Commandant of the Marine Corps, while so serving, has the grade of general without vacating his permanent grade.

((c)) The Assistant Commandant has such authority and duties with respect to the Marine Corps as the Commandant, with the approval of the Secretary of the Navy, may delegate to or prescribe for him. Orders issued by the Assistant Commandant in performing such duties have the same effect as those issued by the Commandant.

((d)) When there is a vacancy in the office of Commandant of the Marine Corps, or during the absence or disability of the Commandant—

((1)) the Assistant Commandant of the Marine Corps shall perform the duties of the Commandant until a successor is appointed or the absence or disability ceases; or

((2)) if there is a vacancy in the office of the Assistant Commandant of the Marine Corps or the Assistant Commandant is absent or disabled, unless the President directs otherwise, the most senior officer of the Marine Corps in the Headquarters, Marine Corps, who is not absent or disabled and who is not restricted in performance of duty shall perform the duties of the Commandant until a successor to the Commandant or the Assistant Commandant is appointed or until the absence or disability of the Commandant or Assistant Commandant ceases, whichever occurs first.