Since the core of combat works precisely as it does in AD&D, I need not go into too much detail regarding how to hit, how to calculate modifiers to hit, how to do damage and how to calculate modifiers to damage. All weapons cause the damage which the player’s handbook indicates is done to small creatures; damage is not modified in its effect against large creatures. Why this particular rule was ever invented continues to baffle me. If the purpose was to make it easier to kill large creatures, why give large creatures more hit dice?
Regarding hit points and hit dice, I suggest looking up my rules on mass effects on hit points per hit die, which can be found here.
Rules regarding surprise in my world can be found here.
Initiative is very similar to the manner in which it is stated in the DM’s Guide, but for clarity let’s put up a few images. The primary manner in which initiative differs in my world is that it is rolled only ONCE per melee. For clarity, “melee” is here defined as an uninterrupted hand-to-hand encounter between two or more fighters. The key word here is ‘uninterrupted.’
AD&D, as I have played it for a long time, suggests that each “side” rolls a d6 to determine initiative, and that this is done each round. I propose that each side still rolls initiative, but that this needs to be done only a minimum number of times. First, let us consider the following situation:
Albert (white), Bertrand (blue), Calvin (green) and Dennis (orange) have all come together and are about to fight. Let us presume all four men have a movement of FOUR. Let us say each of these men represent a different “side.” All four of them roll a d6, and by chance, three of them roll a “3”; and the last combatant rolls a “2.” Bertrand is the odd man out.
Let us also say that Albert has a dexterity of 16. This gives him a +1 bonus on his die. If his dexterity were 17, he’d get a bonus of +2, and if it were 18, he would get a bonus of +3. In this case, however, he only gets +1 and his initiative roll is “4.” The other three combatants have a dexterity of less than 16, so they do not get a bonus.
Albert has initiative, so he draws his short sword (1 move), takes a step to the left (1 move) and attacks Bertrand (2 moves):
We’ll put an X there for convenience. Because D&D is a turn-based game, it does not matter that the other combatants do not move during this time. It is assumed that no matter who moves and in which order, when Albert moves to his left, Bertrand is there and can be attacked. Albert rolls to hit and misses.
Now it is presumed that both Calvin and Dennis are moving simultaneously. It assumes that no matter what is the result of Calvin’s action, or what is the result of Dennis’s action, both actions will be judged to have happened. Thus, even if Calvin attacks and kills Dennis, Dennis still has the opportunity to attack and perhaps kill Calvin also.
It gets tricky if both Calvin and Dennis want to move into the same hex. There are a number of ways to resolve this: 1) Have them write their actions ahead of time, and have them roll to “win” if the actions conflict; 2) Judge the combatant with the higher dexterity to move faster, and thus enter the hex first. I usually play (2); it is easier. If the dexterities are equal, then I rate them by intelligence; if that is equal, then by wisdom; then by strength, then by charisma, and finally by constitution. Why that order? No particular reason. A different order could be argued, though I imagine most would agree on dexterity being first. It doesn’t matter, really, so long as it is consistent.
If you want to get really gritty, a third method might be to employ the following table, a holdover from long ancient wargames:
If we presume that Calvin wishes to get out a battle axe (2 moves) and Dennis wants to get out his two-handed sword (3 moves), then we can further assume that Calvin can move before Dennis, and would then enter an adjacent hex before Dennis could. Or else, Dennis could enter a hex while Calvin was still getting out his axe, and then get out his weapon. I can tell you, however, it is usually better to get your weapon out before moving.
In this case, Calvin pulls his axe and moves 1 hex towards Bertrand (he really hates the color blue). This takes three moves; he only has 4, and he chooses not to move further, so he stops and ends his turn. Dennis gets out his massive sword, has one move left, and uses it to move towards Calvin.
Finally, Bertrand moves (last). He draws his hand axe (1 move) and attacks Albert (2 moves). He misses. He has one move left, which isn’t enough to break from combat, so he stays put.
Now, at this point AD&D would have everyone roll initiative again, but I say it is not necessary. The original order was not resolved by any of the participants meaningfully changing the combative “initiative” of their opponents. If Albert was pressing the attack before, he should be able to go on pressing it until something happens which ends that initiative - something concrete, not for the sake of its own randomness as initiative works in AD&D rules. My argument is that this can only be done by someone doing damage to Albert. This has not happened, so Albert still has initiative.
HOWEVER, the initiative between Calvin and Dennis was never resolved. We know they both go after Albert. They both go before Bertrand. But since simultaneous movement is interesting only in small doses (which is why we keep it), we have Calvin and Dennis roll initiative against each other. We’ll say that Calvin rolls one better than Dennis, and wins the initiative.
So Albert would go first, followed by Calvin, followed by Dennis and finally Bertrand. And this continues until they quit, they die, or one of them is STUNNED. Stunning rules shall be discussed in the next post.
UPDATE: I've had to write more points on initiative before getting to stunning. These can be read here.