Say you have a U.S. submarine that is secretly deploying mines in the Strait of Hormuz. To what extent would non-combat crewmembers such as a cook or doctor aboard the sub know what’s going on?
Would they even know where the sub is in the world (within, say, a 500x500 mile square)?
Edit: “Lowest” may not be the best word, more like “unrelated”
It depends on which country’s Military we are discussing.
Many US troops are well-informed. It improves performance, sharply.
Many Middle Eastern Troops learn essentially nothing, with the Officers getting various levels of information.
Egypt lost in the Seven Days War with Israel in part because most of the Junior Officers & Troops believed they were going into the desert for training only, & were taken utterly unprepared by the Israeli Air Force, who did far worse damage to the Egyptian Army that the Japanese did to the US Navy at Pearl Harbor.
The Egyptian Troops were marching in formation, & had taken no antiaircraft protection efforts at all, nor even unpacked their rifle ammunition.
Communication in the ranks counts.
The answer is in varying degrees depending upon numerous different circumstances. If you are captured and tortured, and you divulge information critical to the mission’s success, that’s bad. On the other hand, if you are captured or killed because you lacked the vital information necessary for success, that’s bad also.
The short answer is that it depends on the mission in question.
As a junior officer on a U.S. submarine years ago, I stood watches in the control room where I knew exactly what was going on, as well as supervisory watches in the engine room. (I was the Engineering Officer of the Watch, or EOOW).
During some “super-secret spy missions,” the guys in the engine room would sometimes ask what was going on. They weren’t exactly prohibited from going into the control room (when they weren’t on duty in the engine room), but they were discouraged from doing so if they didn’t have a reason to be there…plus it was crowded enough in there without superfluous personnel.
Anyway, the standard joke response to the questions from the guys in the engine room was, “Shut up and push.” 
Also, U.S. subs don’t have a ship’s doctor. They have an Independent Duty Corpsman (IDC) instead, basically a medic with extra training.
I imagine that it’s all somewhat dependent on what jobs the people in question have, and at what level.
For example, in the case of a major offensive it is probably critically important that the regimental commanders knew what the overall plan was (break through, turn the German flank). But that’s not necessarily germane for a battalion commander to know. However, it would be good for them to understand the divisional plan and objectives. Similarly, a company commander would need to know what the regimental plans/objectives are, and a platoon commander might need to know battalion level plans and objectives. Your average infantryman would need to know what his company is trying to do. Knowing that the overall Army level attack plan is to break through and turn the German flank near St. Lo doesn’t really benefit him much, but knowing that his company objective is to capture X village by tomorrow at noon is, even if his platoon and squad objectives are even smaller scale than that.
A submarine might be the most extreme example. Not sure how differently things work on a sub different from a surface ship, but on a surface ship, if you want to know where you were it would be pretty easy.
Not long after I got off the USS Ranger, they sent her into the Persian Gulf for support of Desert Storm. The crew was well informed of where they were going and what the mission was expected to be.
Considering the foot traffic in and out of the bridge and the speed of scuttlebutt around a Navy ship, the position of the ship would never be a secret. We have brand new sailors, out to sea for the first time taking box lunches up to the bridge at times. Electricians pretty much ended up everywhere. Some of the other fresh air snipes were also everywhere on the ships.
But the general crew of a carrier and its escort fleet we would never know that a mission was planned to blast a factory or power plant in Basrah. Maybe after the fact, especially if it was successful.
So a man was strolling through town when he noticed some workers tearing up a street. Curious, he decided to stop and watch for a bit. He saw a guy with a backhoe dig a ditch, then a few minutes later, a guy with an earth mover would come and fill the ditch in. Over and over, they dug and filled, dug and filled. Finally, the man couldn’t take it any more. He went up to workers and asked them what the deal was. One of the workers looked at him, shrugged and said, “The guy who was supposed to lay the pipe called in sick.”
Knowing what your job isn’t enough. You have to know why you’re doing your job.
Presumably you could have a basic idea of what the plan is, or know a few or a great many further details. At some level someone knows what the other plans were, why this one was chosen, logistics and any number of other details. I would guess as you get further from this less is known, but am really just spitballing here.
In any secure operation, one where there is classified information, the rule is always that you only find out on a need to know basis. It doesn’t matter what clearance level you have, that just determines what you can’t know. But even with an appropriate security level clearance you only find out things that you need to know to perform your duties.
Clearly this has some latitude, if you will perform your duties better, there is good reason to know. But leakage of classified information to someone not cleared for that level should not happen.
That really surprises me. You are stuck under water with no outside assistance. Seems you would really want a legit doctor on board. What happens if someone needs surgery? (if only an appendicitis?)
Maybe the navy figures almost any damage to the sub is lethal to everyone…why waste a doctor there?
I dunno…hard to understand the thinking here.
On a boat full of healthy and fit young people there is unlikely to be much call for ordinary doctoring. People of service age often go for decades without need for seeing a doctor. Surgical emergencies in peacetime are never going to be handled aboard. A single doctor on board performing an appendectomy would be pretty unacceptable in modern medicine. In the modern world most are done laproscopicly and you would expect a specialist surgeon, an anaesthesiologist, and a surgical assistant in attendance. The days of generalist medicine is long gone. Perhaps in Antarctica, where there is no physical safe way to get a patient out, or a doctor in, you get issues. But I would expect a sub to rendezvous with a surface vessel, transfer the patient off, and then get underway again. Handling that on board isn’t doctoring. It requires a specialist, which is a paramedic. Same guys that will manage the most common needs on board, which is going to be physical injuries.
The Russians have just shot footage aboard the ISS for a movie with a plot based on getting a surgeon up to treat a stricken cosmonaut. Standard movie trope, surgeon would appear to being played by a very attractive blonde actress.
So, by this thinking, there should be no doctors on any ship except a ship dedicated to medical care.
I’m willing to bet you can still find general practitioner doctors. Especially in the military where they cannot call on specialists in a field hospital.
Eventually ships get big enough. Aircraft carriers, LHDs, as well as specialist medical support vessels. They will have dedicated medical capabilities, including surgical and simple x-ray. They will serve the rest of the fleet.
But much smaller vessels than that, quite likely no. Servicemen in peacetime would reasonably expect as good a medical care as modern medicine can provide. The downside is that modern medicine is highly specialised. Nobody goes digging about inside someone without prior diagnostic imaging.
I’m sure you watched M.A.S.H.
How did they do it? How is it done today?
Surely, even today, we cannot expect advanced medical facilities near a battlefield with mass casualties.
Extend that to a submarine. Even young, healthy men can get sick or injured. You are in a tube, hundreds of feet below the surface of the ocean and hundreds of miles from help. A doctor would seem a worthy addition to the crew.
Of course. My father served as a base medical doctor on a UK airforce base just after WW2. There is lots of ordinary doctoring done. But most is non-urgent. In a conflict zone, you don’t need a GP. You want a specialist in trauma, stabilisation and surgery. And lots of paramedics that specialise in keeping the injured alive in order to get them to a field hospital. Servicemen with colds, skin rashes, even cancer, get treated at a base same as ordinary folk.
MASH did have x-ray machines. But not exactly modern medicine. Remember the running complaint was “meatball surgery.” But this wasn’t peacetime. (OK, technically it wasn’t a war, but a police action, but it wasn’t peacetime.)
MASH was a success in reality because it got critically injured casualties attention before they could die. But it wasn’t aboard a ship. It was the equivalent of a hospital ship serving a fleet as close to the action as was safe to be.
In reality we still create MASH like setups. But we can fill them with much more technology. We avoid “exploratory surgery” if we can.
Again, you have to ask what he can add to the situation that a trained paramedic does not. Seriously ill patients should be evacuated. In the modern world most seriously ill patients are not treated by a GP. They are referred on. GPs have not done surgery in many decades. A submarine is not set up for nursing care of a seriously ill patient. Eventually you run the numbers. How many young fit servicemen get sick or injured? What are the illnesses and injuries? How many can be usefully treated on board to the point the casualty can return to active service without external intervention? How many more could return to active service on board without external intervention if a doctor was on board? Is this worth the extra body on board a sub?
My reading is that the numbers just don’t stack up.
Thanks.
A great example of why the SDMB remains one of the best places on the internet.
But is he referred to as “doc”?
Yup. 
So basically, a matter of scale. One doctor for X patients. IIRC an aircraft carrier has about 5000 crew. That (plus dealing with the rest of the task force) might justify a full-time physician. A little over 100 on a submarine, no.