House Rules: Active Combat System for D&D

About three or four sessions into my current campaign, I noticed that my players didn't really like the abstract nature of D&D combat. No matter how much narration and dramatizing I did, combat just felt too passive to them. Specifically, they wanted to do something besides stand there and take it while the enemy rolled against their AC.

Now, one thing I'll say in favor of D&D combat RAW. It's streamlined. And if the players are happy enough to fill in the blanks by imagining feints, dodges, and other maneuvers happening in between declared actions and combat rolls, then it's fine. 

On the other hand, way back when I was a wee player, I had the same reaction. I kept trying to declare dodge or parry on the enemy's turn, and it took a little while for me to get comfortable with everyone rolling against a static number to simulate combat.

Which is probably why I gravitated to Kevin Siembieda's Palladium System games so strongly. Divisive as hell within the RPG community, absurdly crunchy, and badly imbalanced even by early 80's game design standards, the Palladium games nonetheless had a gonzo weirdness to them that I loved. Even though I could never get my early groups to accept a sci-fi/fantasy mashup like Rifts, I bought sourcebooks for everything under the Palladium sun, mining some of the stranger fantasy elements for my own D&D games. 

As I was also getting heavily into anime at the time, I had a special fondness for the Robotech line. At one time I owned every single sourcebook Palladium published for it, despite my regular group having even less interest in it than Rifts. 

Anyway, my old group's strict definitions of what fantasy was and wasn't—and their almost fanatical opposition to genre mixing of any kind—is a subject for another time.

But if there's one thing I always thought Palladium games got 100% right, it was the opposed roll combat mechanic. Yeah, it kind of broke when scaled up to higher levels. Tracking multiple character actions, plus massive amounts of Armor SDC, Character SDC, and Hit Points got to be a pain in the ass. Especially after level five or so. 

But the basic idea of the defender being allowed to dodge by beating the attacker's d20 roll was—and is—gold. And even though I was never able to convince my players to pick up a full Palladium game, a variation on that opposed d20 roll has been a longtime house rule of mine when running D&D.

For one thing, it keeps the players from feeling like combat is just an abstract game of roshambo. Every time I've introduced it at one of my tables, the players get much more involved in the battles. They suddenly feel like they're playing for stakes. 

I also feel it does a better job of simulating the "grit" of combat. Armor as damage reduction just feels more intuitive than armor making someone harder to hit. It also means armor wears out over time. It's an expendable resource that has to be managed, like water, food, and torches. Not to mention the need to find an armor smith in between battles. Suddenly, long journeys into unknown territory become a much more dangerous affair. 

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So without further ado, here's my house-ruled Active Combat System. It's basically a stripped-down, bare bones version of Palladium's more intricate combat mechanics. If you're already familiar with those, then you won't find much new here. 

1. All Players and Monsters get two combat actions per round. 
2. Actions can be used to Attack or Defend, meaning a character can expend both actions on Attack, both on Defense, or one on each.
3. Ascending AC is assumed. Additionally, every type of armor has an Armor Point value (30 for leather, 60 for chain mail, 80 for plate mail, etc.) 
4. Determine initiative as normal.
5. Attacker declares target, rolls d20 to hit.
6. If the target is going to defend, the defense roll (d20) must be rolled AT THE SAME TIME. Otherwise, it's assumed they're just allowing the shot to come in. 
7. Add all bonuses. Attack bonuses are handled RAW. Dexterity bonus is applied to defense rolls, as is any magical bonus. 
8. If the Defense roll is higher than the Attack roll, the defender successfully dodges or parries the attack. Initiative passes to the next player or monster in the sequence.
9. If the Attack roll is greater than the Defense roll, the attack is successful. Additionally, any unopposed roll of 5 or greater (after bonuses) is considered a hit. Much like RAW, a naturally rolled 1 always misses, and a natural 20 always hits, regardless of bonuses or penalties. 
10. If the character or creature is not wearing armor, roll damage and subtract from hit points. 
11. If the character is wearing armor, then the total attack roll (with bonuses) must be higher than the Armor Class to bypass armor and affect hit points (i.e. 14 for leather, 16 for chainmail, 18 for plate mail, etc). Otherwise, damage is subtracted from Armor Points. Note: Creatures with "natural armor" such as a scales or thick hide just use their normal AC.
12. Armor reduced to 0 Armor Points is considered destroyed and worthless. Any character wearing it is considered unarmored for purposes of defense. Unopposed attack roll of five or greater, and all Attack rolls that beat the characters Defensive rolls, will deal damage directly to Hit Points. 

​Once the DM has a handle on it, this system is actually much simpler than it looks. Doing the opposed rolls simultaneously doesn't really take any longer to resolve than rolling against a character's AC. It adds a layer of player participation to the combat round, without adding much more bookkeeping. 

It also affects combat in some interesting ways. With each character only getting one chance to defend in a round (or two, if they forego an attack), mobs of low level enemies like goblins suddenly become a deadly threat to even the highest level characters. Sure, the first twenty or thirty hits will get eaten up by that nice, expensive suit of chainmail. But remember, once it's rendered useless, any undefended roll of 5 or greater is a success. It won't take long for those little bastards to make hamburger out of the toughest warrior under those circumstances. 

It hasn't happened in my current group yet, but as armor gets torn to shreds and healing spells run out, a fighting retreat often becomes the smartest course of action. I've seen the tanks form a barrier, using both actions to defend just so they can buy time for the other PCs to escape. 
  
In short, these rules force the PCs to be much more careful about their tactical situation. It won't be a good fit for everyone's table. Hell, it hasn't even been a good fit for all of my tables. But if your players are starting to see combat as a repetitive slog, then it might be just what your group needs.