[Icelander]

Sentry removal has happened in the real world, but like many other swashbuckling tricks that WWII commandos were fond of, it is much, much rarer now.

Part of it is that we no longer have hundreds of thousands of soldiers in lines of battle facing each other, with nightly raids on the enemy lines. Running the numbers, it is very probable that both WWI and WWII each had an order of magnitude (or more) more commando raids on static posts patrolled by regular soldiers than the half-century since they ended.

Another part is that with new technology, it is become increasingly unlikely that even a perfectly successful use of Stealth + combat skills to disable a sentry will actually allow a team to infiltrate what he is guarding. It is much easier now to hide static sentries with NVGs where they see other guards, use video cameras to the same end, have sentries periodically check-in with an all-clear sign and so on.

In fact, against any kind of competent opposition, it is very dangerous to assume that stealthy infiltration will even be possible. If at all practicable, an assault with overwhelming force is simply a better choice, as it doesn't rely on superior individual skill or even luck as much. If you have the men and technology, just go in with speed and firepower and you won't have to take the same kind of risks as with sentry removal.

Because it is a very risky thing to do. Even if you have reasonable confidence that the Stealth skill of your operator will be superior to the Per or Observation of any sentries*, you also have to be confident that your Observation skill is so much better than the Tactics of the defending commander that you will spot all defenders whose field of view the stealthy operator has to cross.

And it is a lonely and terrifying job to crawl over the no-man's land, syncronising your movements with the glances of your target, while hoping to hell that your intel is good enough so that no one is drawing a bead on your back as you do so.

Miss one hidden guard or even just a concealed camera, and you can have an operator as far as he can get up the proverbial creek without a paddle as the alarm is raised by means of an aimed burst of fire at him as he moves into position behind the targeted guard. Even if no one manages that, just the lights going on and more guards coming running while he is forward of any support can be scary enough.

Even with ultra-competent characters in games set in the real world with magic, 500-600 points of facing the Unknown and living, the PCs generally shy away from that kind of stuff. Observation and Stealth at 18+ might allow them to move into position and a grappling skill and knife skill at 16+ are probably enough to successfully perform one of the sentry removal techniques from Fairbairn Close Combat Systems, but no amount of awesomeness on their part can really insure against such things as hidden cameras, sensors or just really good radio discpline on the part of the defenders.

By contrast, awesome PCs in lower tech settings do it all the time, because the risk is just not the same. If they get detected while moving into position, guards will have to charge into position and then their back-up can do them same. And being caught with a knife in your hand is not as terrible against a sword that the opponent still has to draw as it is against an assault rifle in his hands.

*Which really requires Stealth 15+ and can go up to Stealth 18+ if you think that any of the sentries might be very competent.