What was a "commodore admiral"?
A commodore admiral was a military rank of the U.S. Navy and U.S. Coast Guard that existed for less than 11 months during the year 1982. The elimination of the Navy's commodore rank in 1899 led to captains being promoted to a "rear admiral, lower rank" (two-star admiral), but paid as a one-star admiral. In the early 1940s, the rank of commodore was for a short time re-instituted as a one-star rank in the Navy and Coast Guard, but promoted captains were still advanced to the rank of rear admiral, lower half. At the end of World War II, the rank of commodore was suspended.
The new rank of commodore admiral was created as a means to appease the other three branches of the U.S. military, who felt that promoting U.S. Navy and U.S. Coast Guard captains to a one-star rank, yet entitling them to wear the insignia of rear admiral, was unfair. When the new rank was created, many in the leadership of the Navy and Coast Guard felt this rank violated over a century of tradition. Because of the push back, the rank of commodore admiral was changed to commodore in 1983, then the rank was abolished completely in 1985. The rank of rear admiral, lower half was reinstated with a one-star insignia.
The rank of commodore admiral was one of the rarest in the history of the U.S. Navy, one notable officer to hold that rank was Rear Admiral Grace Hopper.