Rear admiral (United States)

The uniformed services of the United States are unique in having two grades of rear admirals.

Rear admiral (lower half)
In the United States Navy, the United States Coast Guard, the United States Public Health Service Commissioned Corps, the National Oceanic and Atmospheric Administration Commissioned Corps, rear admiral (lower half) (RDML) is a one-star flag officer, with the pay grade of O-7. Rear admiral (lower half) ranks above captain and below rear admiral. Rear admiral (lower half) is equivalent to the rank of brigadier general in the other uniformed services, and equivalent to the rank of commodore in most other navies.

Rear admiral
In the United States Navy, the United States Coast Guard, the United States Public Health Service Commissioned Corps, the National Oceanic and Atmospheric Administration Commissioned Corps and the United States Maritime Service, rear admiral   (RADM), also referred to as rear admiral (upper half), is a two-star flag officer, with the pay grade of O-8. Rear admiral ranks above rear admiral (lower half) and below vice admiral. Rear admiral is equivalent to the rank of major general in the other uniformed services.

History
In 1981, expanded commodore from a title to an official permanent grade by creating the one-star rank of commodore admiral. After only 11 months, the rank was reverted to just commodore but kept the one-star insignia. Then in 1985, renamed commodore to the current grade of rear admiral (lower half). Up until 1981, all rear admirals wore two stars on their shoulder bars and rank insignia. Since then, rear admirals (lower half) wear one star while rear admirals (upper half) wear two; verbal address remains "rear admiral" for both ranks. On correspondence, where the rear admiral's rank is spelled out, an (LH) and (UH) follows the rear admiral's rank title to distinguish between one and two stars.

The Navy, Coast Guard, and NOAA Corps use the rank abbreviations RDML (one-star) and RADM (two-stars), while the Public Health Service use the abbreviation RADM for both. The flags flown for rear admirals of the unrestricted line have one or two white, single-point-up stars on blue fields for the lower half or upper half, respectively. The flags of restricted line officers and staff corps officers have blue stars on a white field. and  officially lists the two-star grade as rear admiral and not rear admiral (upper half). However, the four uniformed services tend to list the rank as rear admiral (upper half) to help the general public distinguish between the two grades.

United States Maritime Service
Although it exists largely as a maritime training organization, the United States Maritime Service does use the rank of rear admiral (upper half) and rear admiral (lower half). By law, the Service has the same rank structure of the United States Coast Guard, but its uniforms are more similar to the United States Navy.

Statutory limits
U.S. Code of law explicitly limits the total number of flag officers that may be on active duty at any given time. The total number of active duty flag officers is capped at 216 for the Navy. Some of these slots are reserved or set by statute. For example the Deputy Judge Advocate General of the Navy is a rear admiral (upper half) in the Navy. In the Coast Guard, the Chief Medical Officer is also rear admiral (upper half). In the Public Health Service Commissioned Corps, at least half of the Assistant Surgeons General are rear admiral (lower half) and no more than half are rear admiral (upper half). Officers serving in certain intelligence positions are not counted against the statutory limit.

Promotion, appointment, and tour length
To be promoted to the permanent grade of rear admiral (lower half) or rear admiral, officers who are eligible for promotion to these ranks are screened by an in-service promotion board comprising other flag officers from their branch of service. This promotion board then generates a list of officers it recommends for promotion to flag rank. This list is then sent to the service secretary and the joint chiefs for review before it can be sent to the president, through the defense secretary for consideration. The president nominates officers to be promoted from this list with the advice of the Secretary of Defense, the service secretary, and if applicable, the service's chief of staff or commandant. 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 extremely rare. The Senate must then confirm the nominee by a majority vote before the officer can be promoted. Once confirmed, a nominee is promoted once he or she assumes an office that requires and/or allows an officer to hold that rank. For positions of office that are reserved by statute, the President nominates an officer for appointment to fill that position. For the Navy and the Coast Guard, because the one-star and two-star grades are permanent ranks, the nominee may still be screened by an in-service promotion board to add their input on the nominee before the nomination can be sent to the Senate for approval; for the two commissioned corps, they normally go directly to the Senate. The standard tour length for most rear admiral positions is three years, but some are set at four or more years by statute. Since both grades of rear admiral are permanent, the ranks do not expire when the officer vacates a one-star or two-star position.

Tradition
By tradition in the United States Navy, when an officer is selected or appointed to flag rank all current Navy flag officers write the selectee a letter congratulating him or her for attaining flag officer status.

Retirement
Other than voluntary retirement, statute sets a number of mandates for retirement. All one-star officers must retire after five years in grade or 30 years of service, whichever is later, unless they are selected or appointed for promotion or reappointed to grade to serve longer. All two-star officers must retire after five years in grade or 35 years of service, whichever is later, unless selected or appointed for promotion or reappointed to grade to serve longer. Otherwise all flag officers must retire the month after their 64th birthday. However, the Secretary of Defense can defer a flag officer's retirement until the officer's 66th birthday and the President can defer it until the officer's 68th birthday. 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.