The United States Navy

Sailors prove they have mastered skills and deserve responsibilities by completing Personnel Qualification Standards (PQS) tasks and examinations. Among the most important is the "warfare qualification", which denotes a journeyman level of capability in Surface Warfare, Aviation Warfare, Naval Aircrew, Special Warfare, Submarine Warfare or Expeditionary Warfare. Many qualifications are denoted on a sailor's uniform with U.S. Navy badges and insignia.
• Commissioned officer
Commissioned officers in the Navy have pay grades ranging from O-1 to O-10, with O-10 being the highest; those with paygrades between O-1 through O-4 are considered junior officers and O-5 and O-6 as senior officers. Officers in the O-7 to O-10 range are called flag officers or "the admiralty". Promotion through O-8 is based on performance in an officer's current paygrade, which is recorded in "FITREPS" (fitness reports). Promotions to Vice Admiral (O-9) and Admiral (O-10) are based on assignment to specific positions and subject to U.S. Senate confirmation. Above the rank of Admiral is Fleet Admiral, which was awarded to only four officers in World War II and is intended to be used only during a declared war. In 1899, a special rank called Admiral of the Navy was created for Admiral George Dewey, a war hero of the Spanish-American War, with the condition that it would cease to exist upon his death. Commissioned officers originate from the United States Naval Academy, Naval Reserve Officer Training Corps (NROTC), Officer Candidate School (OCS), and a host of other commissioning programs such as the Seaman to Admiral-21 program, the Limited Duty Officer and Chief Warrant Officer Selection Programs, the United States Merchant Marine Academy, or receive direct commissions via Officer Development School (ODS) or from its reserve component, the Direct Commission Officer School (DCO School).
Commissioned officers can generally be divided into line officers and staff corps; line officers can be further split into unrestricted and restricted communities. Unrestricted Line Officers are the warfighting command element and are authorized to command ships, aviation squadrons, and special operations units. Restricted Line Officers, on the other hand, concentrate on non-combat related fields, such as engineering and maintenance; they are not qualified to command combat units. Staff Corps officers are specialists in fields that are themselves professional careers and not exclusive to the military, for example: medicine, science, law, and civil engineering.