I haven't read The Riddle of Steel -- I've only read about it -- but I was under the impression that it was fairly involved, and that there was quite a bit to learn about the system before you'd be effective in combat.
It really wasn't that complicated, at least not initially. The paradigm of it was a radical departure from most rpgs so that took some doing to get used to, and toward the end they started adding more and more variant rules and stuff, kind of how DnD evolved from 1E to 3.5E
The biggest holdup on it was that they made the magic system too freeform for most people, and the company Driftwood Press which bought the game never finished the redesigned Magic supplement they were supposed to do.
The thing I did is designed for 3.5 OGL, I think it's fairly easy to understand for people who play DnD, though there is still a slight paradigm shift. I started a thread on the most radical aspect of the combat mechanic
here.
Or would a HEMA hobbyist immediately know what tactics to choose?
The designer, Jake Norwood, is one of the top longsword fencers in the world, (though he hasn't done it in a while he's on his second tour in Iraq right now) but by my estimation 95% of the people who played didn't know the first thing about HEMA or any martial art, the logic of the game just happened to be based on HEMA techniques. So they kind of picked it up the way we all picked up the idea of a saving throw or a cure light wounds spell playing DnD.
The HEMA part was pretty easy to pick up. The weirdest aspects of TROS (like the magic system) came from the indy game design scene at the Forge wherin the game incubated.
G.
FULL DISCLOSURE: I was involved in TROS about midway through its life cycle, I wrote the weapons encyclopedia in
The Flower of Battle which was the third (?) book for The Riddle of Steel, and part of another book they did. I know Jake Norwood personally and consider him a friend. We've fenced together several times.