The same as anyone else, based on their hand to hand training. I’ve had an answer kicking around the draft pile for a couple weeks, that just won’t come together talking about stealth in more detail. But the short version is a kind of, “there is no spoon,” mess.
Stealth is one of those things that gets horrifically misrepresented in media. It’s not about being invisible, or simply staying out of sight, it’s about tricking other people into not noticing you. This sounds like an academic distinction but it’s really not.
Stealth comes in basically one flavor; camouflage. From a hunter playing pretend soldier with their .308 rifle, to actual snipers in ghillie suits, to ninjas in their black garb… actually, the there’s a joke with ninjas, so we’ll get back to that in a bit.
Camouflage in rural environments works off a simple concept: your brain processes where objects are by finding the outline. It doesn’t matter how smart you are, it’s our visual Achilles heel, like animals that can’t see non-moving objects, if something doesn’t have an outline, our brain can’t figure out what we’re looking at.
Camouflage, normal “I spilled paint and coffee on myself” camouflage, works by messing with your outline. Modern digital camo designs do the same thing, incidentally. Outside of the intended environment, it won’t work, but when some of the colors start getting close to the colors around it, the person becomes substantially harder to pick out. It’s basically just an optical illusion armed with high powered weaponry.
Now, when someone moves you’ll still see them, camo or no, because movement is still a pretty solid way of identifying objects in your environment as something that wants to eat you, and your brain is hardwired to react to that, but even then, camo will make it harder to accurately shoot someone. Simply because it’s harder to judge distance and exact position.
Which brings us to the other kind of camouflage, looking like you belong there. Ghillie suits are those swamp mops that you’ll see snipers wearing in some media. The trick is, in these suits, properly outfitted, a sniper actually looks like part of the environment. You can see them just fine, but you don’t notice them (unless you’re looking for “tree tumors”), because they actually look like something that belongs there.
For reference: tree tumors are snipers that have nestled themselves up against trees, and are trying to blend into it. From what little I know on the subject, I’m guessing the major risk is that they won’t actually match to the tree’s outline, or soldiers patrolling the area are more likely to notice that the tree doesn’t look right anymore and investigate. Either way, it’s something that instructors drill out of their trainees.
I said the “other kind of camouflage,” because, really, this is stealth. In an urban environment, being invisible is more about looking like someone who’s supposed to be there, than pulling on a skintight leather outfit, strapping IR goggles to your head, and hanging from the ceiling with oddly brand coordinated firearms.
Infiltration is about looking like you belong until the last possible moment, and then getting out before anyone realizes something’s off. You can’t do that in a catsuit, but you can do it in a regular suit and tie, or a maintenance jumpsuit, or a lab coat. It’s all about looking like you belong. Tragically, there are few places your characters will want to infiltrate where disguising themselves in an S&M outfit will work.
I mentioned ninjas earlier, because there is a joke there. Actual ninjas would disguise themselves as laborers, farmers, servants, or other peasants and would sneak in that way. The black garb you probably recognize would have been a fantastic disguise if they were assassinating an actor in a play, but would have had limited utility outside of that. But, that’s also the joke.
The black garb is actually a Japanese stagehand’s outfit. These are the people who would be on set moving stuff around, and adjusting the scenery in a play. That was their job, and it was understood that you weren’t supposed to be watching them because they weren’t actually part of the play. So, as a viewer, you’d filter them out, and ignore them. And then one of them would stab a character, because it was a ninja, in the play, who had disguised themselves as something you’d never suspect; one of the stagehands.
Somewhere in the transition to film and TV, the stagehand outfit came along, either as a gag or an homage, and spilled over into more and more media. The actual black backdrops of the stage productions were gone, it wasn’t actually camouflage anymore, but the outfit had become a visual shorthand for, “you can’t see me, I’m a ninja.”
Anyway, apologies about running late on this one tonight.