Before I get to lighting fires on the USS Theoretical, let’s run through the organization of a smaller warship. Many of the names of the divisions were different on different ships, so if you know of a ship that had different names for divisions, that’s fine.
The Captain, also known as the Commanding Officer: On frigates and smaller destroyers, the Captain was a commander. Cruisers and large guided-missile destroyers were considered to be “major commands”, the Captain had the rank of captain and that was a second command tour job. The officer commanding any commissioned naval ship was the Captain, even if it was an ocean-going tug and the Captain was a lieutenant. Captains generally served 24-month tours.
The Captain is responsible to the outside world for everything that happened on the ship. The Captain could have been sound asleep in his rack when something bad happened, but he still swung for it. Only landlubbers and naval aviators referred to a ship’s captain as “Skipper.” To the Captain’s face, you called him only that. “The CO”, “Charlie Oscar” or “the Old Man” were acceptable terms to use to refer to the Captain, but never in his presence
The Executive Officer: The XO was the officer who was responsible to the Captain for the good order and discipline of the ship. The XO ran the administration of the ship, made sure it was kept clean, and personally inspected the berthing, messing and galleys of the ship on a daily basis. Being an XO was as close to a thankless job as there was. XOs served 18 month tours and were lieutenant commanders on all ships from frigates to cruisers.
Departments were headed by Department Heads. Department Heads were graduates of what was once called “Destroyer School,” then renamed “Department Head School” in Newport, RI. It was the only Navy surface officer school that was long enough to merit a “permanent change of station,” which mean the family could come with. In the 1970s, when retention sucked, the Department Heads on LSTs and some auxiliary ships were second-tour division officers.
Department Heads served split-tours; 18 months on a frigate or small destroyer as a first-tour lieutenant, 18 months on a large guided-missile destroyer or cruiser as a lieutenant commander. There were other second-tour jobs, such as a staffie on an afloat destroyer squadron or cruiser group staff.
Of the three line department heads (Operations Officer, Weapons Officer and CHENG), the senior one also served as Senior Watch Officer. The Senior Watch Officer was responsible for the training and staffing of all in-port watches and all underway watches outside of the Engineering Department, unless the Senior Watch Officer was also the CHENG. In reality, the watches in Radio Central, Sonar Control and CIC were the responsibility of the respective division officers, but they had to answer to the Senior Watch Officer. A young officer was well advised never to make the Senior Watch Officer mad, unless the young officer wanted to be in charge of an in-port watch section full of morons, malingerers and all-around dirtbags and wanted to stand underway watches with people he or she despised.
Division Officers ranged from ensigns fresh from Surface Warfare Officer Basic School in Newport, RI to full lieutenants on split tours. They were nominally in charge of their divisions; their real job was to learn how to manage people, to qualify as an underway watchstander and to qualify as a Surface Warfare Officer (SWO or, as the aviators put it, a "black shoe"). Tours ranged from single-tours on one ship for a minimum of 36 months to spit-tours of 24 months and eighteen months. Some did split tours of 30 months and 18 months, for four years at sea. This was the initial separation point between those who had potential and those who were wastes of oxygen.
Now, for the departments and divisions:
Engineering: Read this and this.
Operations: The Operations Officer headed this department. Operations Department was made up of these divisions:
OC Division: This was the communications division, the radiomen (RM) and the signalmen (SM) were in OC Division. Radiomen did not talk on the radios, they tuned them up and patched them to the remote stations on the Bridge, in CIC and elsewhere. The radiomen ran the teletypes, sending messages off the ship and receiving them. Back in the day, this was done by HF morse code; the radiomen typed up the messages as they came in. After World War 2, the use of HF TTYs came into use. In the 1970s, satellite UHF TTYs replaced most use of HF TTY, though HF was used for backup purposes and for training. The signalmen worked the flag signals, they used semaphore and flashing light.
OI Division: OI Division had one space: the Combat Information Center, “CIC” or”Combat.” The sailors, once known as radarmen, were now “operations specialists” or OSs. They plotted radar contacts, maintained the status boards, plotted sonar contacts, controlled aircraft, and did most of the talking on the radios, other than the tactical freqs on the Bridge.
OE Division: OE Division fixed the equipment that the radar and radio girls broke. They were the Electronics Technicians or ETs, a rate that got them no end of grief once a certain Spielberg movie came out. The Electronic Warfare technicians (EW) were usually part of OE Division.
OT Division: This division was only on larger ships, it was the Cryptologic Technicians or CTs. I officially do not know what they did, but they seemed to come and go as the ships went near different regions of the world. The division officer was a restricted line officer, not eligible for command at sea. Being a CT officer was a specialty job.