These rules are changes to allow for a more realistic feel to combat in the AD&D game. They can be used in conjunction with the Armor System in another section, but work very well without them. The Defense Pool, Defensive Combat and Defense Rating rules may be a bit too much for some DMs and players, due to the many possible combinations the player can opt for, and the many numbers involved. For those who enjoy this added versatility, and can handle the math without annoyance, use them as they are explained below. For those who do not want to go through the hassle, I present an easy way to both use the rules as written below, yet prepare beforehand a simple combat sheet for each PC. This sheet will allow quick reference for the DM and player during combat, while still allowing the Combat System to work at full effect. After reading the Combat System below, just click on the link to this easy combat reference sheet.
This combat system uses a few terms I will define below: Base AC, Defense Pool, Defensive Combat, Defense Rating, Opposed Attacks and Unopposed Attacks.
Base AC represents the AC the defender gets without actively defending himself. If you do not use my Armor System, then armor would modify this base AC, as well as defenses that simulate armor, like bracers of defense. Otherwise, only plus oriented protective magic will modify this base AC, so rings/cloaks of protection, displacer cloaks, protection from evil spells, etc. all modify the base AC. Shields, pluses on them and shield like magic defenses, like the shield spell, do not modify base AC, but are a part of the Defensive Pool detailed later. The defender gets this base AC against all attacks, even back attacks. This base AC can be further modified by the Defense Pool below.
Defense Pool represents the defensive bonus a defender has due to his active defense and dodging or blocking. If the defender would not get this AC bonus if attacked from behind, you can bet it belongs to this Defense Pool. Dexterity bonuses, swashbuckler bonuses, monk defense bonuses, single weapon style bonuses, Defensive Combat bonuses(detailed later) and shield bonuses name most of the bonuses that belong here. Add up the total AC bonuses these various defenses would grant the defender normally, not including the Defensive Combat bonus, as it is best to keep it separate and just add its defensive bonuses separately, since it can change from round to round. This total is the Defense Pool of the defender. Each round it is renewed, and each round the defender can allot these points to defend against attacks. None of these points can be applied to flank or rear attacks, thus, these will always strike at the defenders base AC. Each defense pool point must be applied to each attacker the defender faces, as a defense point only works against 1 attacker per round. Thus, if a defender is attacked by 3 orcs, all from the front, he must split his defense pool among them as he desires. In some cases, a single attacker may be so skilled as to count as more than 1 attacker, such is the case when an attacker gains true multiple attacks, due to skill in his weapon. Each attack he has in this way counts as 1 attacker for this purpose.
So, for example, Thor is a warrior with an 18 DEX(4 defense pool points), who is a swashbuckler(2 points to the defense pool) and uses a medium shield(3 points to the pool) in which he is proficient(1 extra point to the pool). Thus, all told, Thor has 10 points in his defense pool. Assuming he has no magic defenses or armor(if not using my armor rules), his base AC is 10. So, if he faces a single orc with 1 attack, he can put all his defense points against it, for an AC of 0(base of 10 - points from pool(10) = effective AC against that attack). If he faces 2 orcs, he would need to defend against each separately, and assuming even defense, he would put 5 points against each, so his AC would be 5 against each orc. Rear or flank attacks allow none of these points to be applied so they all strike the base AC 10.
Defensive Combat bonuses are those granted to skilled combatants. Basically, as a combatant learns to become more skilled in his weapon and combat, he learns an even mix of defensive and offensive fighting skills. Thus, fully half of his training is geared toward defense. This is where the defensive combat bonus comes from. Combatants can opt to use some of their combat skill toward defense rather than offense. The usual AD&D game assumes all is used in offense, but this system gives combatants a choice. To find the maximum defensive combat bonus a combatant can gain, first, find their base THAC0, only modified by any to hit bonus from weapon mastery. Strength, magic or any other bonuses to hit are not counted for this. Find this THAC0, and subtract it from 21. This gives the improvement in skill the combatant has earned. Half of this skill improvement can be used for defense. Just divide this number by 2, rounding all fractions down. This gives the Defensive Combat Bonus the combatant can use. Note this value on the sheet near the weapon THAC0, and then add it to the fully modified normal weapon THAC0 of the combatant. Yes, this makes the combatants THAC0 worse, and this modified THAC0 becomes his new THAC0. The combatant must decide how much of this Defensive Combat Bonus to apply to attack(THAC0) and how much to defense(defense pool). Whatever is applied to attack, reduces his THAC0 by that much for that round and what is left over(if any) is added to his Defense Pool. These left over points, which are added to the defense pool, act just as Defense Pool points, and cannot be applied to flank or rear attacks.
For example, Thor is a 7th level warrior specialist in sword. His STR is 18/00, and his sword is +3. His normal THAC0 is 7. To find his DCB(defensive combat bonus) we find his THAC0 only modified by the +1 from specialization. This is 13. We take this and subtract it from 21, so 21-13 is 8. Divide this by 2 and we get a DCB of 4. We take this and add it to his original THAC0, and we see that Thor now has a THAC0 of 11 with a 4 DCB. Assume he is attacked by 1 orc. He can put all 4 points to defense so his AC against the orc would then be 4 better, and Thor would attack with an 11 THAC0 for the round. Now suppose 2 orcs attack. To defend, Thor decides to use all 4 points for defense, which he spreads evenly among the 2 attacking orcs, so 2 points to each, for a 2 point better AC against each. His THAC0 would be 11 since he chose to use all 4 DCB points for defense.
Defensive Rating this rating determines how effective you are at self defense. To find it, simply find how many attacks you are allowed per round(count only basic number of attacks, off-hand attacks do not count). Add 1 to this rating if you are specialized in a fighting style that gives you a free parry/dodge each round. Martial arts style D, shield/weapon style, and Bladesinging style(if the free parry option is used) are 3 examples of styles that would give this 1 point bonus to defense rating. This number is your Defense Rating. This rating tells you how many attackers your combatant can defend against normally and not be overwhelmed. Every attacker directed at you that exceeds your DR(defense rating) is considered unopposed, and gets a +4 bonus to hit. You can still allocate defense pool and defensive combat bonuses to these unopposed attackers, if allowed(front hexes only) and if you choose, but they still get a +4 to hit due to your inability to actively defend against them properly. This means being outnumbered or outskilled presents a problem to a defender. Another catch to this DR is that to apply a DR point to an attacker so as to oppose him and not give him a +4 to hit, you must use an attack or parry/dodge against that attacker, as many as you wish DR points applied. Because you cannot attack or parry/dodge flank or rear attacks, these attacks ALWAYS act as unopposed attacks, and get the +4 to hit. In addition, rear and flank attacks receive another +4 to hit on top of this bonus, for a total of +8 to hit!
Rear Attacks are special not only in that, as for flank attacks, no defense pool or active defense(defense rating above) can be applied against them, but also in that at the end of any round a foe threatens your back, regardless of how it happened, that foe gets an immediate attack of opportunity(a free attack). This only occurs at the end of the round(very slow phase), so if warrior can get his back covered before the round ends, he can probably avoid having a foe get this free attack on his back. Just remember, foes can move freely when not threatened, so if a warrior simply pivots to turn his back away from an attacker behind him, yet no one threatens the attacker to keep him pinned down, the attacker can simple move over(have such attackers save their half move until the end of the round) and get that free back attack. Being surrounded really sucks!
For example, Thor is now surrounded by 6 pissed off orcs. He has 2 attacks per round, and a free shield parry each round as well, because he is specialized in shield/weapon style. This means he can actively defend against 3 attacks each round(DR of 3) assuming the attacks are in his 3 front hexes, since he can only attack or parry/dodge attacks in these front hexes. Poor Thor has 6 attackers to defend against. He can use his active defense(DR) against up to 3 of them, since they are in his front hexes. So, his DR of 3 allows him to defend against the 3 in front of him, so they will not get the +4 to hit bonus that unopposed attacks get. This means that the other 3 will get the +4 to hit bonus because they are not actively defended against by poor outnumbered Thor. Next, comes the defense pool and defensive combat bonuses Thor will use to defend himself. Regardless of how Thor spreads his defense pool and defensive combat points, these can only apply to the 3 front hexes, so the 2 flank and 1 rear orc only need to hit his base AC, without defense pool or DCB modifications. Thor uses all his DCB for defense, giving him 4 points, these are applied against the front orcs as Thor desires, along with his usual defense pool points. Since he has 10 defense pool points, he has a total of 14 points to divide among the 3 front orcs for his defense. He goes for even defense, so applies 4 points to each orc attack, and decides to apply the remaining 2 against the middle orc, which means each side front orc must hit AC 6, since Thor has base AC 10, minus his defense of 4 against each side front orc. The middle orc has 6 points against it, so it must hit AC 4. The flank and rear orcs only need hit his base AC 10 and get a +8 to hit on top of this because their attacks are unopposed and from the flank/rear. Thor is in trouble. In addition, if an orc can maneuver so as to be behind Thor at the end of the round, he gets a free attack!
Body Shields/Medium Shields these 2 shields can allow the user to apply up to half of his shield defense pool bonus against the shield flank attacker. This is the only exception to the rule that defense cannot be applied to flank or rear attacks. Only the bonus from the shield applies, not any other defense pool or defensive combat bonuses. A body shield always allows this, while a medium shield will also, but only if the user is both proficient in it and in shield/weapon style. These shields also allow parries/blocks to be applied to the shield flank, but are at -4 to hit for the parry attempt.
All Monsters and Dodge/Blocks
All monsters can give up any 1of their attacks(if it is a paired attack, both are given up) to block, but must give up all their attacks(assuming they get only 1 attack sequence per round) to dodge. Some monsters may get a free dodge or block, depending on their martial skill. This is up to the DM.
This is the basic Combat system, and my Armor System goes well with it. If you have questions or want more, go to the rest of my web pages.