Am I correct in believing that "Lords of Men" (as an add-on to the ArM5 core) is pretty much the most-complete combat mechanics (barring magical combat) for ArM5? That there are no other sword/bow/brawl/etc/etc/etc rules?
Or have I missed something?
Thanks!
IIRC the brawl manoeuvres were only in the core book, but I might be wrong
I seem to remember hearing the Houses of Hermes: Sociatas has rules for invisibility in combat... but otherwise, yeah, I think everything about combat is in the core rules and Lords of Men. Some of the LoM rules were reprinted in Grogs, but nothing was added that I could see.
Houses of Hermes: Societies has a chapter on spells in combat, with much more detail on invisibility, attacking from stealth, spells that need to penetrate vs. ones that don't, etc.
Lords of Men contains a lot of additional rules for weapon combat, all of which are optional and some of which are even directly contradictory to each other (presented in a 'you could do this... or that' way). It allows for more detail if you want it, but I would caution its use with not letting your players wave it around as 'the combat chapter.'
Grogs contains some useful additional information for things 'around' combat, such as examples of the use of the Concentration ability for people who don't cast spells, or why you want to have a range of abilities rather than just piling xp into single weapon.
In both cases, I'd recommend starting with vanilla ArM5 combat and then deciding which bits irk you and looking at enhancing to those areas.
The Optional Combat Rules chapter of LoM is a bit confusing, with so many... well, options, for delaying and interrupting actions, and things like that. Even though some of them are useful and in general the chapter includes valuable information, you must choose carefully what options to apply, or combat will get quite complicated. (Yeah, I know, that's why they're optional...).
On the other side, I found the information in Grogs very useful, even though it does not apply specifically to combat. I think a summary of the first chapters should be handed to every new Ars troupe to understand that "being a grog" is not "being a bunch of weapon stats"...
Yeah, that's what I'm doing ... 
right here right now. Looking at enhancing those areas. :mrgreen:
I've been in Ars Magica since the ArM3 days, was among the 5e playtesters, have been RP'ing for over 3 decades now, own dozens of systems.
All versions of ArM have had -- to me -- inadequate combat mechanics. It's not enough to chase me away from the game -- hell, it's not even enough to dethrone ArM from the role of "my favorite game EVAR!!!" But some ideas that have been kicking around for a while are finally beginning to coalesce... 
Well, I've always felt that was the point... de-emphasizing combat mechanics in favor of a complex magic system. Make combat simple and generic, so not too much thought or game time needs to go into the grogs holding off the pack of demonic wolves until the magus can cast Demons Eternal Oblivion.
Especially since that magus has Slow Caster or Disorienting Magic flaws, or something that slows him down...