Most US naval combatants use their own crew to provide security. The entire crew is trained to some degree or other in small arms.
In port, those crew assigned the collateral duty of Reaction Force are given much more detailed training, including ship-board tactics and, and then they’re drilled repeatedly to ensure they know how to do their jobs. Rescue and Assistance Detail, at least on the ships I served, was an adjunct to Reaction Force, and formed the core of any boarding or shore team. R&A were also trained in shipboard combat, but had additional duties, such as firefighting, medical assistance, and so on. Basically, if a team had to leave the ship to help another ship or deal with a pier-side situation, the R&A Detail took first crack at it, followed by such duty section as was required. Reaction Force never leaves the ship on their duty days. On sister-section duty days, the sister section Reaction Force might be called off the ship to provide security for such activities as moving ‘Special Weapons’.
I was a member of the R&A detail for years, serving as Counter-Sniper, Hose Team Leader, and Medical Assistance Team Assistant, as required by circumstance. In charge of the R&A detail in my duty section was the Duty Section Leader, in my case Chief Petty Officer Burdette (a real character!), and we had a total force of fifteen bodies on average. Reaction Force was handled by the Duty Weapons Officer, usually a Warrant Officer or Lt (jg), usually with a force of ten to fifteen bodies. Both R&A and Reaction Force respond to the CDO (Command Duty Officer), which is an At-Sea Officer of the Deck officer, and could be as junior as a Lt (jg), or in some cases, as senior as the Senior Watch Officer (usually the Navigator), a full Commander.
Backing all this up is the Duty Master At Arms, and the Duty Waepons Section personnel, another fifteen to twenty personnel.
What does that mean? On the ship I’m discussing, out of a crew af roughly fifteen hundred, in six-section duty (~500 per section), there is aproximately twenty five to thirty immediate responders, able to choose their muster location from the armory, or one of several sattelite armories if the main armory is inaccessable. There is an additional fifteen to twenty immediate reserves, then the rest of the duty section to call upon. Weapons range from light cannon to heavy machineguns to light machineguns to heavy automatic rifles to light rifles to handguns to PR-29s, to firehoses & fire extinguishers (very effective in some cases!), to improvised weapons of opportunity (no shortage of potential bludgeons!).
So: 40 to 50 ready forces, and then ~450 backups, commanded by a experienced deck officer, and two experienced junior officers/senior enlisted. if a special weapons move is planned, there might be an additional thirty armed-and-ready personnel guarding the weapons area as long as the move is going on, supplied from the sister duty section.
Out to sea, it’s rather different. Then, the Weapons Dept is responsible for security, the Master At Arms for internal good order and discipline, and the Flying Squad for immediate medical or fire-related emergencies.
Scale these forces by the size of the ship and crew.
All ships of any appreciable size have some form of medical department, even if it’s only an Independant Duty Corpsman (read: Highly trained, highly skilled, and cabable of handling most any casualty or illness, right up to some simpler surgeries). On the ship I’ve been discussing, we were supporting a full squadron of submarines, so we had a full-up medical staff, about fifteen corpsmen, two dive corpsmen, a half-dozen pharmacist-specialist corpsmen, two full physicians (one a Lt. Commander, one a Lt or Lt(jg)), a dentist (typically a Lt), and half a dozen Dental Techs or so. Now, mind you, as a tender, we were the local clinic for our boats, but we were backed up by a full-scale regional Naval Hopsital. This is similar for the surface fleet, one tender is fairly similar to any other. Aircraft carriers will have larger medical departments, as they have much larger crews, and often serve as the principal medical resource for an entire battle group. A carrier’s medical dept might be commanded by a full Captain. Fleet Marine Force medical depts will be even larger, as each small unit has their own Independant Duty Corpsman, as well as the ships medical dept, which is prepared to recieve & treat significant battlefield casualties.
Hospital ships are only used in support of land-combat operations, and then only when anticipating massive casualties, and when the need is anticipated well in advance, as the hospital ships spend most of their time in stand-down mode.
That help any?
