How realistic is it for the retired agent/spy/assassin to come back and kick just as much butt as they did years before? Does such training come back to you easily if you haven't used it in a long while or will you be rusty enough to get killed?
Parts of this are realistic, others not so much.
If you’ve spent enough time training techniques, this stuff gets baked into the way you move. It’s not, “oh, I’ll do this to someone;” it’s just there. Training can also affect how you look at the world; this is true as a general statement on life, but it also applies here. Again, as with muscle memory, this is always there, always affecting how you view your surroundings and the people in them.
So, in that sense, yes. A veteran character coming back after years away from the job will still have their skills and training. Some of that will be rusty, but this stuff sticks with you. Especially if you were maintaining your training for years. That said, they’ll still get their teeth kicked in.
Ironically, one of the more realistic takes I’ve seen on this was in the middle seasons of 24. In the early seasons, the protagonist, Jack Bauer, is a federal counterterrorist agent. After the third season he’s basically on his own, and no longer a part of the agency that trained him. By the fifth season (about 3 years later) he’s at a point where he’s getting his ass handed to him by a security guard.
The problem is something we’ve explained, repeatedly. Hand to hand combat is not static. The training I got 20 years ago doesn’t apply now. It will work against untrained opponents. Basic physiology doesn’t change. However, going up against opponents who’ve been keeping their training up to date, (or are some of the people responsible for updating the techniques in the first place), is not going to end well.
Something I know we haven’t discussed on this subject is how this updating happens. It requires contact with people who are actually using their training practically. Seeing what people are doing isn’t something that you can do sitting on a mountain top. You need to actually be immersed in the community. You look for how people are adapting to the techniques you’re training others in, and look for ways to get around those counters.
In the case of law enforcement, one major source if intelligence to guide updates is watching what criminals are teaching each other in prison. Career criminals will look for ways to counter police hand to hand, and once they have that, will (usually) share it with people they work and/or socialize with.
A veteran coming in after years away may be able to execute their training perfectly, and still get taken down by a rookie who received their training last year, because they were trained to counter the veteran’s approach.
Updating is about looking for the things that are most prevalent, and finding ways to defend against them. It’s very likely your veteran will understand this concept. Whether that affects their behavior is more of a characterization question.
Incidentally, this doesn’t just apply to hand to hand, it’s also a relevant concept when you’re talking about things like tradecraft.
Tradecraft is the shorthand for techniques used in intelligence gathering. It’s (somewhat) all encompassing. So, anything from social engineering to dead drops or even the way you set up surveillance could be lumped in under this header.
Just like hand to hand training, this stuff does go out of date. Usually once someone’s actually exploited a method and gotten caught doing it. Though, sometimes it’s preventative.
The irony is, when it comes to being a spy, the biggest problem is being a veteran, not being out of practice. It’s being a veteran. When a spy starts their career, no one knows who they are, they have no reputation, they’ve never turned up in strange places, they’re just someone walking around, taking in the sights, maybe doing a job for some NGO.
Even if a spy is never caught, as they work, their name will start ending up on desks, in lists of witnesses, employees, or whatever. Once is not a pattern, but as their name keeps coming up over the years, it becomes easier to identify them. Potential enemies start keeping files, and gradually filling them with what they know. This means it is much harder for a veteran spy to operate in the field undetected, than it is for a rookie.
There’s a similar issue for assassins. Either they’re a complete ghost, no one knows who they are, and may not even believe they ever existed, or (more likely), if they were working for a government (or any other large, overt organization, like a corporation), they’re in the same boat as a veteran spy. People may not know your character is an assassin, but they will know that they worked for someone. Which in turn, will put them on guard, and make your character’s life much harder.
There are concepts a veteran will have internalized, which someone without training won’t understand or grasp. Thing that just don’t go out of style. For example, bullets will blow through most residential walls and furniture. So, if someone’s taking cover behind a couch, kitchen wall, or car door, it’s far more expedient to simply shoot through whatever’s in your way. Another concept is one I’ve mentioned recently, you reload when you have the time, not when you’ve run your gun dry.
Similarly, experience they’ve learned from may still be relevant. Being able to read someone’s intentions, know when they’re about to resort to violence, or simply knowing the value of good intelligence aren’t going to go away because your character spent the last five years pretending to be a well-adjusted human being.