In contrast, in most other nations' rank-bearing services, the term "rear admiral" refers exclusively to two-star flag officer rank.

[4] In the United States uniformed services, rear admiral (lower half) replaced the rank of commodore in 1985.

Instead, they preferred the term "flag officer", in order to distinguish the rank from the traditions of the European navies.

During the American Civil War, the U.S. Congress honored David Farragut's successful assault on the city of New Orleans by creating the rank of rear admiral on July 16, 1862.

[citation needed] During World War II, the U.S. Navy and the U.S. Coast Guard both had a temporary appointment, one-star rank of commodore, that was used in limited circumstances.

Both the Navy and the Coast Guard divided their rear admirals into "lower half" and full rear admirals, or "upper half", the former being paid at the same rate as a one-star brigadier general in the U.S. Army, U.S. Marine Corps and the newly independent U.S. Air Force.

However, both categories of rear admiral wore two-star insignia, an issue that was a source of consternation to the other services.

L. 99–145 renamed commodore to the current grade of rear admiral (lower half) effective on November 8, 1985.

However, the four uniformed services will sometimes list the rank as rear admiral (upper half) to help the general public distinguish between the two grades.

[11] By statute, Congress has expressly limited the total number of flag officers that may be on active duty at any given time.

[13][14][15] A newer statute enacted in 2016 lowers the cap on the total number of active duty flag officers in the Department of Defense to 151, effective December 31, 2022.

[22] The President may nominate any eligible officer who is not on the recommended list if it serves in the interest of the nation, but this is uncommon.

For the Navy, Coast Guard, and NOAA Corps, both grades of rear admiral are permanent ranks and do not expire when the officer vacates a one-star or two-star position.

Flag officers typically retire well in advance of the statutory age and service limits, so as not to impede the upward career mobility of their juniors.