For a long time, I think I've harbored a fundamental misunderstanding about how D&D combat works, or at least was mostly designed to work. It's taken me a while to put together all these pieces into a coherent theory, but (I hope) I finally have a good enough handle on it to explain it now.
It's never explicitly stated in B/X that an attack roll doesn't represent one discrete swing of the sword. In fact, there are a lot of factors that mistakenly imply that one attack roll does in fact represent a single attempt to do harm. There's the terminology of "hit" and "miss." There are monsters with multiple attacks, explicitly labeled "claw, claw, bite," implying that the creature attempts to strike exactly once with each of them during a round. Even the initiative roll implies individual blows, with one combatant taking a swing at the other, and then the other counterattacking.
Of course, ten seconds is quite a long time in the frantic scuffle of combat. Go ahead, count it out - one-thousands or Mississippis or whatever method you favor. While you do this, imagine a sword fight in real time. I'll wait right here...
Did you imagine one person swinging a sword, and then the other swinging in return? Of course not! You probably imagined a complex dance involving many thrusts, slashes, and parries, circling and jockeying for position, ducking and weaving, tripping, shoving, stumbling, off-hand punches, and dirty tricks. In D&D combat, all of this is neatly subsumed in a minimal number of die rolls: a d20 attack roll vs. a static Armor Class number to determine if each combatant was able to effectively wear down his opponent, and if that succeeds, a damage roll to determine by how much. A successful attack doesn't even necessarily mean that the attacker "hits" or threatens the opponent once and only once with his primary weapon. A fighter with sword and shield who scores a successful attack may do damage by thrusting with his sword, but also by bashing with his shield, kicking his opponent in the knee, tripping his opponent to the ground, ramming him against a wall, or some combination of these and other possible moves.
The upshot of all this is that not only is B/X combat abstract, it abstracts by aggregating actions within a unit of time. It does not attempt to narrate a blow-by-blow of combat through game mechanics; it resolves the general outcome of ten seconds of battle and leaves any narration to be done on a post hoc basis. The dice tell you how much attrition of stamina each combatant inflicted on the other, but the precise "how" can only be explained after game mechanical resolution. Choices consist of broad tactical options rather than discrete maneuvers - to fight, retreat, or flee rather than whether to attack with primary or secondary weapon, parry, feint, or trip the opponent.
In contrast, many rules, both official and house, have been put forth with the goal of increasing the range of choice and the excitement of combat. A large number of these add options to perform specific actions and maneuvers and resolve them game mechanically within the combat round. For example, BECMI D&D (the heir to B/X) introduced a weapon mastery system that allowed characters wielding certain weapons at a high enough level of master to deflect attacks by making a saving throw vs. death ray. This certainly can be exciting, rolling to escape all damage from an attack in the moment as it occurs, but it also violates the basic assumptions of the abstract ten-second round by correlating each attack roll with a single discrete attempt to do harm.
This sort of granularity can be a slippery slope indeed. Are we to assume that unless a character has and uses the deflect ability no parrying takes place during a combat round? Or are we arbitrarily singling out one parry of many in the round for mechanical resolution, and if so what is the justification for hand-waving the rest? To move to a system of individual maneuvers rather than an abstract aggregate requires a lot of arbitrary decisions or assumptions as to where each action begins and ends and which ones are significant enough to warrant their own mechanical resolutions. Since these determinations are necessarily arbitrary, it opens up the possibility for all kinds arguments unresolvable by mere reason, and the ugly head of DM fiat must be reared. A combat round is, of course, also a purely arbitrary interval of time, but the potential for argument is limited to how long it should be. I imagine there are plenty of players prepared to go to the mat over their characters' signature combat moves, but very few who would bother to protest vociferously that the combat round is the wrong number of seconds.
It actually is possible to increase the range of player choice and agency in combat without short-circuiting the abstraction of the ten-second round or increasing the granularity of combat. Tactical options can apply to the entire round, and are best done with flat modifiers rather than additional dice-rolling. For example, an option to fight cautiously might grant a bonus to AC and a penalty to the attack roll. This simulates the character taking a conservative approach, passing up questionable opportunities for offense in order to concentrate on defense and deny offensive opportunities to the opponent. Reversing the modifiers simulates an aggressive approach, in which the character presses any perceived advantage at the cost of possibly leaving himself open or falling for a feint. Even though the choice only modifies two die rolls (character's attack roll and
opponent's attack roll) - in fact, because it only modifies the standard die rolls of a combat round rather than adding more - it applies to everything that character and his opponent do in that round. The round is still resolved abstractly and in aggregate form; the players aren't calling specific maneuvers, but they do have a little more say-so in the outcome.
Telecanter's simple combat maneuvers can fit neatly into this framework as well, by interpreting the player's declaration of intent not as a specific maneuver but as a desired goal of a round of combat. It doesn't violate abstraction, because the player is not choosing simply to do a single maneuver, but integrating a goal into the cut and thrust of the combat round. Even if the character doesn't accomplish that intent, normal damage my still be inflicted by all . The round is not assumed to be taken up by a single action. If Bob the fighter wants to disarm his opponent, he isn't making a roll specifically to disarm; he is declaring that he wishes to make that one of the possible outcomes of the round's combat. He's stating that if the opportunity arises he would prefer to disarm the opponent than to inflict damage. Whether or not that opportunity does arise in a form which Bob can capitalize on is determined by the attack roll; if it doesn't, Bob hasn't necessarily done nothing else in the round. He has ranked his priorities, and taken whatever his opponent and his own level of skill allows him to take in that round.
I have some more thoughts on the implications of the abstract ten-second round on multiple attacks, damage, initiative, and monsters with more than one attack form, but those are probably best saved for the next post.