Phaser Control crews in the 2260s are shown in Command Gold (see below). 24th-century officers of the Judge Advocate General, such as Phillipa Louvois and Rear Admiral Bennett are also in Command Red. Intelligence officers such as Worf and “Rota” are in Command, as is Sloan when he appears to work for Internal Affairs. Worf also brings the role of Strategic Operations into the Command Division. And numerous 24th century administrators, including Ensign Weldon, Commander Hilliard, and then-Commander Benteen, are shown in Command (though see below).
The trend we see developing here is that the Command Division encompasses roles that range from administrative to real-time control — all involving some level of command decisions, all involving complex situations with many variables. As such, I and others suggest that dedicated diplomatic officers would likely also be in this division, along with dedicated shuttle pilots.
In all cases, we see an emphasis on the complex analysis of secondary data sources. A JAG officer must weigh this legal precedent against that, must compare the strength of this counsel's argument with the other's. An administrator (and starship CO and XO) must balance multiple priorities, coordinate multiple efforts, make executive decisions on which project gets which resources. An intelligence officer must read countless briefings and analyses and meta-analyses, and conduct their own constant analysis of the information at hand. A diplomat has to constantly balance various parties' interests at once, all while appearing equanimous. And a pilot (and weapons control officer) must bear in mind the position of nearby objects, the capacity of the ship’s engines, the strategic requirements of the situation, the physics of starship motion, and the relevant impact of stellar and interstellar phenomena, all simultaneously.
Administrators
The 24th-century trend points towards administrators being part of the Command Division (c.f. Weldon, Hilliard, Benteen). This is consistent with the general idea of needing to be able to multitask, pivot from crisis to crisis, and engage in some level of command/control. The 23rd-century trend points toward administrators being part of the Operations Division — for example, almost all of the yeomen aboard the NCC-1701 — Rand, Colt, , etc. – are shown in the Operations color of their era. Likewise, Commodore Stone and Commodore Stocker, who are depicted as more paper-pusher administrators than Sisko ever was, despite their shared positions as base commanders, are shown in Operations. On the other hand, Commodore Mendez is shown in Command.
There is logic to both approaches — one could imagine a starship yeomen’s responsibilities being more clearly defined (and thus a better fit for Operations) while an admiral’s adjutant may be responsible for handling a wider range of unexpected circumstances (and thus a better fit for Command). The shift between 23rd and 24th centuries may represent a change in Starfleet’s approach, or it may be that different administrative positions fall under different divisions, depending on their specific job requirements.
Admirals
A conversation between Sisko and Eddington in “The Adversary” has been taken to mean that only Command Division officers can rise to captain or higher. This would seem to be generally true, but not a hard and fast rule. Montgomery Scott held the rank of captain while still maintaining membership in the Operations Division, and Admiral Toddman did the same while serving with Starfleet Security. In the 23rd century, Commodore Stone and Commodore Stocker both wear Operations Red, which is consistent with the general trend of that era of putting administrators in Operations rather than Command. Though all these examples represent a minority, it’s clear that there is no hard requirement that captains and flag officers be part of the Command Division. More likely is that the available positions for such ranks skew toward the Command Division — i.e. a primary reason for promoting someone to admiral is to have them be responsible for a large number of people, which is usually a job for an administrative or command expert; there are cases where you would prefer to have an engineering or security expert managing a large number of people, but they are rarer.
Tactical and Weapons Officers
During the 2260s, operation of shipboard phasers was at least partially executed by the Phaser Control crew, a measure perhaps introduced following the Control Crisis of 2257 or possibly as an anti-telepresence mechanism; these personnel wore Command Gold, reflecting their close relationship to the Flight Control department. It is likely that there is significant cross-training between the two departments during this era, during a time when shipboard weaponry was mounted in single location as opposed to arrays, thus necessitating close teamwork between the two. (This would also dovetail with Chekov’s eventual transfer from navigator to tactical officer in the 2270s.)
A century later, the role of the solitary tactical officer has once again emerged, apparently replacing Phaser Control crews, and reflecting a general trend back towards automation. Until the 2370s, tactical officers were again in the Operations Division, likely due to closer personnel integration with the Security Department, and with the Engineering Department, as weapons systems become more reliant on the computer. (For a real-life analogue, consider that accountants of 100 years ago required high mathematical aptitude; nowadays, wizardry with Excel is just as important if not more.)
However, by 2379, Worf appears to be serving as tactical officer again on the Enterprise while still wearing Command Red. It is possible that tactical officers once again moved back into the Command Division during the Dominion War, as battle tactics shifted more toward fleet engagements and away from one-on-one dogfights. In that environment, a tactical officer would be more akin to a multitasking commander.
Comparing The Divisions
The three divisions form a spectrum of fundamental approaches: the Science Division works slow and deep; the Command Division must work broadly and often with urgency; and the Operations Division falls in the middle, emphasizing straightforward practicality.
Both starship commanders and flight controllers must make split-second choices; engineers rarely must do this and scientists almost never. Security and tactical officers will sometimes need to make split-second choices, though mainly under the commands of a senior officer, and almost invariably within the specific confines of their discipline; they are drilled in making the kind of split-second decisions they need, almost to the point where it is automatic. It would be unusual for security to multitask, though less so for tactical officers, which is why we see that role bouncing between divisions. While doctors too will need to make split-second decisions, their approach, as described above, is fundamentally different from those in the command division — in essence, only within the command division is it acceptable for officers to be slightly reckless – scientists, engineers, security personnel and most of all doctors must be more conservative.
Of course, these divisions only reflect the fundamental approaches of basic training, the "starting points" for each officer. Starfleet officers of all backgrounds are expected to grow and diversify their skills; just because someone received scientific training at the Academy doesn't mean that they can never pick up the practical approaches used in operations. An engineer certainly should not shy away from the slow, in-depth style of the sciences, nor should a scientist avoid the interdisciplinary approach of the command division.
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