<P> The Act of Congress of March 4, 1925, allowed officers in the Navy, Marine Corps, and Coast Guard to be promoted one grade upon retirement if they had been specially commended for performance of duty in actual combat . Combat citation promotions were colloquially known as "tombstone promotions" because they conferred all the perks and prestige of the higher rank including the loftier title on their tombstones but no additional retirement pay . The Act of Congress of February 23, 1942, enabled tombstone promotions to three - and four - star grades . Tombstone promotions were subsequently restricted to citations issued before January 1, 1947, and finally eliminated altogether effective November 1, 1959 . The practice was terminated in an effort to encourage senior officer retirements prior to the effective date of the change to relieve an overstrength in the senior ranks . </P> <P> Any officer who actually served in a grade while on active duty receives precedence on the retirement list over any tombstone officer holding the same retired grade . Tombstone officers rank among each other according to the dates of their highest active duty grade . </P> <P> Warrant Officers provide leadership and training in specialized fields and skills . Unlike other nations' militaries (which rank warrant officers as Staff NCO equivalents), the United States military confers warrants and commissions on its Warrant Officers and classifies them into a separate category senior to all enlisted grades of rank (including officer candidates), cadets, and midshipmen . As Warrant Officers are officer - level technical specialists they generally do not exercise command outside of their specialty . Warrant officers come primarily from the Staff Non-Commissioned Officer (SNCO) ranks . </P> <P> A Chief Warrant Officer, CWO2--CWO5, serving in the MOS 0306 "Infantry Weapons Officer" carries a special title, "Marine Gunner," which does not replace his rank . A Marine Gunner replaces the Chief Warrant Officer insignia on the left collar with a bursting bomb insignia . Other warrant officers are sometimes informally referred to as "Gunner ." </P>

What are the ranks in the us marine corps