I don't think reaction time has much to do with a proficient knight. Experience, strength, endurance, concentration, decision-making or even strategy are more decisive in a fight.

@Sasugasm I agree- which is why I think that the changes I suggested would help with all of the traits you mentioned. A knight with good experience, concentration, and decision-making could use a superior reaction time to more easily counter attacks. A knight with 'upgraded' muscles would be stronger, faster, and have more endurance. I hope that helps explain my thinking.

@Sasugasm / Onyz - reaction time is critically important because if you don't react quickly enough to an attack you're dead; even if you perform the correct counter. Indeed, one of the things I do with newer HEMA students when they first start sparring is to tell them precisely where I'm going to hit them, make sure they're ready, and then hit them anyway because they didn't react fast enough.

If you recall, Selmy himself died facing an overwhelming number of underwhelming opponents, so even the trope has its limits

@nzaman Fair point

Some Punisher and Batman comics talk about how fear can be used to submit much larger and better equipped force by yourself, a bit of theathric, some firework, and one or two brutal and cruel death can work wonder on anything not having a death wish.

Reaction time can already be trained for, more important to combat is muscle memory, the actions you take without conscious reaction.

@Ash I suppose the idea that I was trying to get across is that in the context of this question reaction time could be improved enough that you would even have time to think if you needed it.

@Sasugasm I suppose I'd defined it as the time taken to react, rather than splitting into thinking and acting times (as it were), but this is the thing: we had trained (at slower speeds) the correct parry for the cut that they knew I was going to make. Their body knew what to do (every time I've done this they've made the correct movement), they were expecting the cut and were concentrating on it. They just didn't react fast enough.

@Onyz Yup, understand that if everyone has the same level of improvement then you just move the goalposts as it were. Muscle memory is still essential past a certain level of skill to compete with others at that level, but that level is now higher for everyone.

@Ash It isn't free improvement- it would require time and training. Like how you were talking about, but multiplicative.

@Onyz It's free potential that they don't otherwise have.

A somewhat similiar use case; 3 Olympian fencing masters VS 50 opponents

"Realisically not possible"? Example from history: the duel/ambush of Miyamoto Musashi by Yoshioka Matashichiro and members of his clan. Yoshioka had challenged Musashi to a duel: however, before the duel members of his clan armed with swords, bows, and rifles had hid themselves around the site, intending an ambush. Musashi killed Yoshioka with a single blow, then cut his way through the ambushers.

@jamesqf According to Wikipedia, it was the other way around: Musashi arrived early to the duel and hid when he saw Yoshioka had brought an army with him, then he attacked by surprise and killed Matashichiro (a 12 year old boy) and fled from the rest of its company. Still bold, but very different picture.

@nzaman And that's in the show. In the books, Barristan Selmy was never the Master Swordman trope. He was an accomplished knight, but he mostly won one-on-one fights. When outnumbered he was easily taken, like during the battle of the Trident. The ice & fire master swordman type is Silvio Forell.

@Rekesoft: Yes, there's only so much that fits in a comment. But the point is that Musashi faced numerous opponents, even having expected that the ambush was planned.

Real life example: en.wikipedia.org/wiki/Pierre_Terrail,_seigneur_de_Bayard - Despite probably some, ah, embellishments, he did apparently manage to defend a bridge alone against 200 opponents. But as this is real life, he ended up killed by a bullet in the back.

This is possible actually. Monante fighting systems rely on this. I also believe Musashi actually won a one vs many encounter handily when he fought through a few of his assassination attempts. There's no need to make your world any different from ours. Additionally, many sword masters/grandmasters have commented on newer swordsmen being fantastic on the attack, but completely unable to defend themselves from incoming blows. Your Swordmaster just needs to be a guy who knows how to block and uses one vs group tactics. No need for anything else. The Master swordsman trope is not a fantasy.