AD&D 2e combat

It feels high time to get a revision of this post up to overview how combat works in our AD&D 2e campaign. Here are the key points/rules I want to highlight:

• Surprise. Determined by rolling 1d10 for each side (as deemed necessary by the DM) at the start of an encounter; a result of 1-3 means that each opponent gets to make a free round of attacks (using melee weapons, missile weapons, or magic items, but not spells) against the surprised party. Various modifiers can be applied, for example a +2 bonus to account for a cat familiar’s keen senses around a camp at night.
• Initiative. Determined by rolling 1d10 for each side at the start of each combat round. Lower roll wins, with the results indicating the count on which each side will begin its actions during the round.
• Melee and missile attacks occur on the initiative count. Combatants with multiple weapon attacks (e.g., missile weapons with a high ROF and Fighters with weapon specialization) take any subsequent attacks at the end of the round; monsters with multiple natural attacks (such as claw/claw/bite) and PCs/NPCs with two-weapon fighting make all of their attacks immediately. (Note that, if we used weapon speed, the speed factor would be added to the initiative count for each combatant.)
• Movement and charge attacks begin on the initiative count and consume a number of “segments” necessary to complete the associated movement.
• Spellcasting begins on the initiative count and completes after a number of segments equal to the spell’s casting time. If the caster is damaged while the spell is in the process of being cast, the caster’s concentration is lost and the spell is thwarted.
• Other single-round combat actions include turning undead, lightning a torch, drinking a potion, binding wounds, etc. (also see the 2e PH, p 93).

Other/special combat actions and modifiers:

• Attacking from higher ground grants a -1 bonus to initiative and a +1 bonus to attack rolls.
• Charging allows an attacker to increase his or her movement by 50% and make a single attack against an opponent at +2 to hit. In return, the defender gains a -2 bonus to initiative and the attacker suffers a -1 penalty to armor class in addition to losing his or her Dexterity bonus to AC for the round.
• A critical hit occurs when a combatant rolls a “natural” 20 on an attack roll. In these cases, maximum damage is awarded without rolling.
• Firing into melee results in a -4 penalty to attack rolls to account for the difficulty of avoiding one’s allies. (Note that this is not, in fact, “by the book” for 2e. Per the PH, p. 99, ranged combatants firing into melee do not take a penalty, however targets are chosen at random and being hit by friendly fire is possible. This rule probably warrants further discussion.) This post provides details on how firing into a melee actually works.
• Melee combatants may select specific targets for their attacks when the ability to distinguish one opponent from all others is practical (this is up to the DM’s discretion). When it’s not, the opponent being attacked is determined at random. 
• Withdrawing allows a combatant to disengage from melee at 1/3 speed. Fleeing allows the combatant to run from melee at full speed but draws a free attack from each engaged opponent. (In either case, the combatant exiting the melee may be pursued, unless each pursuer is explicitly blocked off by an ally.)
• Invisible opponents can be attacked with a -4 penalty to hit, as long as the attacker is aware of the opponent.
• Prone opponents can be attacked with a +4 bonus to hit. Only sleeping, held, or fully immobilized opponents can be slain automatically.
• Cover and concealment make it more difficult to hit an opponent with missile fire. Cover (or “hard cover”) means that an obstacle (like a wall or boulder) is blocking the intended target; concealment (“soft cover”) means that the target is obscured by entities (such as fog or foliage) that hide the intended target. (See the 2e PH, p. 99 for details and modifiers.)
• A called shot may be made against a target in an attempt to achieve a specific result, such as forcing an opponent to drop an item. Called shots are made with a -4 penalty to hit, and a +1 penalty to initiative.

In closing, while the above points cover the majority of combat situations in our games, I highly recommend that each player read the full “Combat” chapter in the 2e PH (pp. 89-106) prior to our next session.