Real World Definition
In the United States Navy, the United States Coast Guard, the United States Public Health Service Commissioned Corps, and the National Oceanic and Atmospheric Administration Commissioned Corps, commander (CDR) is a senior officer rank, with the pay grade of O-5. Commander ranks above lieutenant commander and below captain. Commander is equivalent to the rank of lieutenant colonel in the other uniformed services.
A Commander in the U.S. Navy may command a frigate, destroyer, submarine, aviation squadron or small shore activity, or may serve on a staff (typically as executive officer). An officer in the rank of commander who commands a vessel may also be referred to as "Captain" as a courtesy title, or informally referred to as "skipper."
Historically, the rank of "Commander" was originally called "Master Commandant" in the U.S. Navy. This rank corresponded in function to "Master and Commander" in the Royal Navy. It was later changed in 1838 to its modern form.
In the U.S. Maritime Service, an auxiliary service, the grade of Commander is appointed by the President via the Secretary of Transportation, making it a federally recognized rank with corresponding paygrade of O-5.
Definition in the Star Trek Universe
Commander is a rank used by the service organizations of many civilizations.
On Earth, this rank has a history dating back to at least the 20th century to the old seagoing navies, and has equivalents used by numerous species and cultures on several planets.
History
As a traditional naval grade in Human usage, commander is the second most senior line officer rank, falling between a captain and a lieutenant. On Earth, the United States Navy used this rank as well as the Royal Navy. A rank of lieutenant commander also existed in these organizations, viewed as a lieutenant granted the authority of a commander. The United States Navy used the insignia of three solid sleeve stripes to denote the rank of commander and considered the rank the equivalent of a lieutenant colonel.
The ancient sea of rank commander was usually given to ship executive officers, department heads on larger naval vessels, or to the commanders of shore installations. The watch station of command duty officer was a position which could be held by a commander. (Star Trek IV: The Voyage Home)
In infantry forces, a commander was any CO.
In Starfleet
In the galaxy, the modern rank of commander is typically held by the first officers of various cultures' starships and is also granted to the commanding officers of the smaller outposts, space stations and starbases.
In Starfleet, a prerequisite to becoming a commander is by taking the Bridge Officer's Test. As commanders prove their leadership ability over time, they are considered for the difficult and highly competitive promotion to captain. (TNG: "Thine Own Self")
Proper naval parlance says that, even if a naval vessel is commanded by an officer whose rank is commander, that officer is still able to be referred to as a captain while on the deck of their own vessel. (DS9: "Behind the Lines")
In the Xindi-Reptilian military of the 22nd century, a commander controlled a squadron and a regiment.
The rank of commander in the Romulan Star Empire is considered the equivalent of a Starfleet captain. (TNG: "Future Imperfect") Also, a subcommander grade exists in the Romulan military, with this rank also used in the 22nd century by the Vulcan High Command.
- According to The Making of Star Trek (page 256) the Romulan rank of commander is the rank of someone who commands a fleet of ships. This would imply it to be equal to the Federation Starfleet rank of commodore.
The 23rd century Imperial Klingon Fleet used the rank of commander to denote the commanders of smaller space vessels, such as a Bird-of-Prey. (Star Trek III: The Search for Spock) A Klingon rank of captain was used for larger vessels with this title carrying over to the 24th century Klingon Defense Force. (TOS: "The Trouble with Tribbles"; TNG: "Redemption")
Use of the rank in Star Trek: Second Fleet Online
The rank of Commander in Star Trek: Second Fleet Online has many uses. They hold senior positions on starbases as department heads, first officer positions on starships that have an officer of the rank of Captain or higher as its commanding officer. It is also the minimum rank in which they can command Escorts, but they would also be allowed to command Surveyors and Scouts. This rank is also offered provisionally in the command division.
In order to achieve this rank in ST: SFO, members regardless of division must pass two of the Academy Scenarios (one Diplomacy and one Battle Simulation) with a rating of Satisfactory or higher.
Members in ST: SFO Holding this Rank
Currently the following members hold (or have held) this rank. Their position is stated next to their name as well.
- Alexandra Preston (former First Officer, USS Berlin NCC-14293)
- Surak (Provisional, First Officer, USS Indefatigable NCC-74626)
Members in ST: SFO that Once Held this Rank and have been Either Promoted or Demoted
The following members once held this rank. Next to their name are the years in which they held the rank.
- Winston Cummings (2369-2373, then promoted to Captain)
- Samsara Steelman (2371, then promoted to Provisional Captain)
Rank Insignia History
Permanent / Full Rank Insignia
| Division | US Navy Insignia (20th and 21st Centuries) | Enterprise Era (22nd Century) | Original Series Era / Star Trek I (23rd Century to 2278) | Original Series Movies (II, III, IV, V, and VI) (2279-2350) | Next Generation Era (2350 to 2366) | Voyager / DS9 (Seasons 1-4) Era (2366-2373) | DS9 (Seasons 5-7 and beyond) (2373 and beyond) | Rank Insignia for the ST: SFO RP |
| Command | 
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| Operations-Engineering | 
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| Security-Tactical | 
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| Medical-Counseling | 
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| Sciences |
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| Academy | This division is NON-CANON to Star Trek and is only used in ST: SFO | 
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Provisional Rank Insignia
| Division | Voyager / DS9 (Seasons 1-4) Era (2366-2373) | DS9 (Seasons 5-7 and beyond) (2373 and beyond) | Rank Insignia for the ST: SFO RP |
| Command | 
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Notes
For the Original Series Movies Era (2279-2350) the divisions were further broken down then what they are today. For today's Operations-Engineering Division, they were broken up into Engineering / Helm (yellow) and Navigation / Communications (Silver). You will also note that the Sciences Division also uses the Silver color for their rank insignia.