Charlie is considered the imminent threat level. Even in that case, weapons are only issued to guards.
Now, if you follow the statements of many CCW advocates, they'll say that you should always carry your gun because you can't predict when you might need it. It seems that military guidelines are in strong opposition to that point of view.
How so? Last I checked military guidelines even in time of peace have armed guards at the base. The fact that they don't arm every soldier says more about how effective they believe their security measures will be to contain hostile situations and their ability to react. The equivalent to the base analogy is how many people believe in remaining armed inside their house at all times (dramatically lower number than concealed carry away from home).
From my time in the Navy, I know that the quarterdeck, or any other additional entry/exit points that may be made available(usually on larger ships) will
always have at least one armed individual on site. As the threat condition elevates, the number of armed individuals increases, and starts to include more than just the 1 armed quarterdeck watch stander minimum.
Which isn't to mention the pier security which has wildly variable levels of security ranging from heavily armed to just having a police baton and a radio. Metal detectors being employed isn't unheard of either, particularly in elevated threat situations.
High security areas on military bases, be it due to either inherent threats posed by the material on site(explosives/weapons), or otherwise sensitive nature of the work that happens, tend to also be "hardened" locations that will be difficult for a lightly armed attacked to gain entry to in the event of those locations being fore-warned of their presence(they'll lock down in advance of their arrival).
Which isn't to mention that in many of those places, having a separate armed security presence on site isn't usual for the more "sensitive" locations, particularly if there is a lot of physical separation between various "Assets" (such as at a military base). Most of the armed security present at most military bases is in the form of security watch standers drawn from the units stationed there, much like the US Navy Warships do to ensure their own respective security bubbles, leaving the base police to oversee overall security and access to the base itself.
I can't really speak to how things work out everywhere, and probably wouldn't even if I could, but the reality is the security situation implemented at every military installation is probably as numerous as there are military installations. Regardless of how much they try to standardize a lot of things. Much like with the Ships in homeport, I imagine there are plenty of comparable situations in Army/Marine Corps/Air Force bases where depending on where you are, the unit assigned to a particular location may also attempt to respond with its own armed response force in addition to anything Base Police may send out to assist.
With almost a 100% guarantee of that in the case of a US Navy Ship being involved, it'll have its own internal response even while the base police are getting contacted to assist, in the event it isn't immediately resolved internally.
But it also goes back to a US Military Base being an Apple and Oranges comparison to the civilian side of things. It would be like setting up a security perimeter around a college campus restricting the number of entry and exit points to campus, with either security screenings or escorts happening prior to even being able to enter the campus. With the further additions of each building on campus having their own additional layers of security to get through, with more than a few departmental buildings containing their own respective (mini)armories and internal "rapid reaction forces"/"security alert team" drawn from staff dedicated exclusively to responding to security threats within their respective buildings.
And actually, for a school shooting situation, that security alert team is kind of what they're talking about when they talk about arming teachers in the classroom. You don't need to arm every teacher, although in some cases that may be a "best" solution as it gives you a greater chance of their being in the same room when the problem starts. You just have to either arm, or make provisions for rapidly arming, several of the teachers in the event of a "situation" developing that warrants that response. Someone already in the building or facility is always going to be able to respond more quickly than someone several miles away.
Yeah, yeah, that's what the (resource) officers in the schools are supposed to be for, but one Cop with a gun is rather limited in their options in comparison to a group of 4+ people with guns tackling the same issue, particularly when those 4+ people are intimately familiar with the general layout of the location in question. But that goes back to things I've alluded to elsewhere, and requires a bit more training than even the NRA has often talked about when they talk about arming teachers.
NRA is more approaching it from a "Warrior" perspective(1 person with the right tools/skills). While I'm talking more from a "soldier" perspective(where a team of people work together to achieve a common objective), and it is that "soldier"/team perspective than even the LEO's would employ once they do get a chance to respond, particularly in the case of SWAT. Which is the thing many people forget about, they get hung up on the "Special Weapons" part of "Special Weapons
And Tactics" the thing that makes SWAT stand above the regular police forces is they typically do additional training beyond just the standard individual training, as they have to train with their fellow SWAT members to learn how to act and react
as part of a unit.