My favourite example of an associated mechanic is the to-hit roll: the player rolling a d20 to-hit maps directly to the PC taking a swing at the monster with his weapon. IME it's very immersive.
The only game that even comes close to being immersive in is GURPS IMO - due to the one second combat rounds.
And that doesn't take into account sword and shield combat. My shield is a weapon. If Hammerborg is right about the way the vikings used their shields (and having experience with sword and round shield I believe he is), the weapon you initally attacked with was the edge of your shield - you then followed up with your sword to exploit the opening you had made. Yes, you read that right. Sword and shield fighting by one of the cultures that took it most seriously you'd attack first with your
shield. Edge on. Swinging your sword at someone was to exploit the opening you've made or the opening they've presented you with.
I won't say the swing is the least important part of the exchange because quite clearly it isn't. But it's the smallest part. And I consider the idea that an attack roll maps directly to a swing to be risible. Because I can swing and attack more than once per minute. Are we fighting using stop motion animation here? If you treat the attack roll as an almost complete abstraction of a six second period including an OODA cycle or two it works but the second you try to say that the attack roll is the swing we're into stop motion animation territory and
extremely diassociated.
In combat your goal is first to create then to exploit openings.
For me the most immersive and the most associated form of D&D melee combat is comfortably the 4e version. The only thing that challenges it is the Book of 9 Swords.
For immersion, to think as my character does, I need to replicate the
OODA loop. Observe. Orient. Decide. Act.
Observe. What is going on around me? This is where AD&D breaks down hard. I update my observations and start a new loop
once per minute. Once per six seconds is ... acceptable if not great.
Orient. This is where 4e and the Bo9S blows the competition out of the water and why I really dislike [MENTION=326]Upper_Krust[/MENTION]'s attempts to generalise powers in play (rather than as a dev tool).
The second O, orientation – as the repository of our genetic heritage, cultural tradition, and previous experiences – is the most important part of the O-O-D-A loop since it shapes the way we observe, the way we decide, the way we act.
You are at your fastest, and therefore your most effective, when you are using moves you have practiced to be instinctual. Breaking it down to a list of pre-determined powers and combinations, not all of which will be applicable in any given situation for reasons the rules are too zoomed out to tell precisely is right for this step. To get the Orient step right you need (a) multiple predefined non-trivial options and (b) for not all of them to be accessible at once. AD&D fails here. 3.X makes a vague stab but because it does it with static feats you don't have the unfolding situations allowing different tricks and combinations, and generally just have one best button. And the Bo9S Crusader structure is better than the 4e AEDU structure, but 4e has deeper and richer options for orientation because they include much more movement and positioning.
Decide: From your choice of actions what do you do? In AD&D for a martial character this amounts to "Target him, mash the 'A' button." Great. Once again this fails anything resembling immersion. (That said, 'quick' is a redeeming feature). In 3.X normal combat it's 'move into position if you aren't already there and choose whether to mash button A or button B'. You use your feat chain to weight one of your buttons and then normally just mash that button - and Full Round Attacks seriously cut your options down. In Bo9S and 4e if you build properly, you decide where to move, how to move, exploiting the relative positioning of enemies, and swing at one then turn back to attack the other is entirely possible for fighters. Positioning in a duel is probably as important as swordwork - and in rolling skirmishes it's probably moreso.
Act: Here's where you roll the dice and see what happens. At this point there's little to choose between them. Better systems on the act scale like WFRP 3e or Cortex/Leverage have two axes to play on - did you do what you were intending and were you lucky or unlucky with it.
So as we can see, mapping to the thought processes, the combat cycle should be
OODA. AD&D it's more like ..da. 3.X it's Ooda. 3.X Bo9S is probably O
ODa and 4e is OO
Da or possibly even O
ODa. (So far D&D Next looks to me as if it will end up as OODa at best, and 13th Age is O
Od
a).
So for mapping my thought processes to the thought processes I would use as a warrior in combat, 4e leaves everything except the Bo9S in the dust. Not that there isn't a lot of improvement to be made - a lighter game using the WFRP 3E engine could get up to O
ODA. But as things stand there's just too much to track.