The Evolution of D&D Core Mechanics
Most people credit 5th edition for being the reason that D&D is so incredibly popular, and they wouldn’t be wrong. Access to the game has never been easier. You see D&D being played in mainstream forums and references to the game abound in pop culture. You can start playing with little to no knowledge of the game rules. Most importantly, the game rules are easy to learn, easy to follow…especially compared to the AD&D and 2nd edition.
This isn’t a post to rant about why 2nd edition is better than 5th edition, how 1e purists have it right, or why 4e is either an abomination or stroke of genius. Everyone has their opinions on such matters and we don’t need another floating around the internet. I am going to talk about something that many new players have heard of but don’t understand. This is the same something that old-timers will either say saved or ruined D&D. It’s the d20 system, and my thoughts about it can be put simply:
Without the original d20 system, we wouldn’t have 5th edition.
In the Beginning
It’s small, but here’s all the class attack matrices. Dungeon Master’s Guide, AD&D 1st edition (1979)
In the early days of D&D, you had charts upon charts, all crammed with the information you needed to make an attack, a saving throw, ability check, so on and so forth. It was a maddening process. Let's take a look at 1e to get a better understanding. When you were looking at your ability scores, you'll notice right away things are going to be a little wacky. Strength scores went up to 18, then increase by percentile dice. Fighters with an 18 strength got to roll percentile dice to give them an additional bonus. A base score of 18 Strength provided you with an attack bonus of +1 and a damage bonus of +2. Now you roll percentile dice. 01-50, and your attack bonus remains at +1, but your damage bonus increases to +3. Why? I have no idea. If you rolled well and got a 96 on the dice, your Strength was listed as 18/96, and you got a +2 attack bonus and +5 damage bonus. A +3 increase in your damage all came down to a great roll on 2d10's.
When combat started, the DM had their hands full. The DMG has four matrices for the various character classes and an additional one for the monsters you'd be dueling to the death. The fun isn't over yet, though. In the PHB, there is a matrix that lists the to hit adjustments for each weapon for each armor class. A club has a -4 attack modifier against an AC 3, but +1 to an AC 10. A halberd meanwhile, has a +1 against AC 3 and a +0 against AC 10. There is a matrix for assassins trying to assassinate someone, a matrix for a cleric trying to turn undead, and don't even get me started on all the psionic charts. None of this includes all the random modifiers found throughout the DMG. For example, a large shield, such as a Norman kite shield, was a +1 to your armor class rating, but the DM could allow the same shield to add +2 to this armor class rating against missiles. Saving throws had their matrix, but I think you get the point.
The Amazing THAC0
THAC0 isn't the mysterious, impossible to understand the system that some people would like you to think it is. Both THAC0 and the d20 system are mathematically equivalent. People also forget that it was a considerable improvement over the previous editions that had combat tables out the wazoo. That doesn't mean that THAC0 didn't take time to learn; it just took a lot less time than the previous system…if you want to call dozens of matrices a system. Here's a quick rundown on how the THAC0 system worked, and you can decide for yourself it was the big bad boogyman people make it out to be.
For those that don't know, THAC0 is the abbreviations for To Hit Armor Class Zero. A character's THAC0 is a fixed number for a given level. It never changes except when your level changes. Just look it up on the chart at first level and adjust it accordingly as you level up. When you attempted to hit something in the earlier editions, you had to follow this system:
Roll a d20 - Simple so far, right?
Add or subtract bonuses or penalties. - What's all the fuss all about?
You then subtract that number from their character's THAC0 value to find the strongest armor class (AC) the attack hits. In AD&D, armor classes range from 10 at the worst to -10 at best, meaning a lower THAC0 value will yield better hits. Ummm, ok?
The Ormyrr - What is that little stick for? Monstrous Manual, 2nd Edition (1993)
So, if the player's character has a THAC0 of 12, and they roll a 13 on the dice (with no bonuses), the formula for figure out how the best armor class is THAC0 (12) - The Player's Roll (13) = Best Armor Class Hit (-1). Here's an example; your 6th level Fighter encounters an omyrr. The ormyrr has an Armor Class of 5, and a 6th level fighter has a base THAC0 of 15 (you can find this information on page 91 of the 2nd Edition Player's Edition, 1989). Using the formula above, you'll need to roll a 10 (15 - 5 = 10) or higher to hit Jabba the Hut's little cousin. Once again, the better the Armor Class, the lower the AC is, which is the opposite of the 5th edition.
Are we having fun yet? Because not all the crazy charts have gone away. Now the 2nd edition makes these charts optional, but they still exist and haunt many a DM's nightmares. One example is the Weapon Type vs. Armor Class chart found in the DMG. Each type of weapon damage (slashing, piercing, and bludgeoning) had a modifier based on the kind of armor the weapon was hitting.
So while THAC0 was a simplification of the rules when compared to combat tables, the d20 system represented a seismic shift in the game's mechanics and their simplicity.
The d20 system
The d20 system came about in 2000. Wizards of the Coast had purchased TSR three years earlier and wanted a return on their 25 million dollar purchase. The problem was that D&D was stagnant at the time, and growth had slowed to almost nothing. WotC wanted to keep the game intact, but make it easier to understand and more comfortable for beginners to play. With the release of the 3rd edition, the d20 system was introduced to the world of tabletop roleplaying games.
So how does the d20 system work? As we all know, each character has six attributes, which are Strength, Constitution, Dexterity, Wisdom, Intelligence, and Charisma. Now, the player would roll a d20 based on one of these attributes, and the roll would answer the magical question of whether or not you were successful in whatever insane action the player was attempting to pull off. Ok, hitting a monster isn't crazy, but trying to run up the side of a wall, lunge at the creature, a sword above your head, and attempting to skewer it is, and we all know as players that is how we describe our "to hit" actions. When you roll a d20, it determines if you were successful with your action based on the roll in relation to the related attribute. Let's make it even easier to understand. The d20 rule system works on this simple core mechanic, so all you had to do is roll the die and follow these simple rules.
Roll a d20.
Add any relevant modifiers.
Compare the result to a target number.
If your roll equals or exceeds the target number, your character succeeds. Lower, you fail. The simplicity is astounding when compared to previous systems. If you want to character to do anything in the game, you now had a straightforward way of figuring out whether or not you were successful in your endeavors. Want to pickpocket the wealthy noble or break down a door or hit that angry troll in front of you? Roll a d20, add the appropriate modifiers, and if you beat the DC or AC, you are successful. Just like that, the d20 system was born, making the game much more inviting to new players. With this system, the DM now had a way to account for and figure out an incredible number of actions.
There are plenty of articles on the internet that will talk about the rise and fall of the d20 system, the WotC Open Gaming License (OGL) for the d20 system, d20 Modern, and all the RPG's that incorporated it into their games. That's more history and company politics than I'm willing to get into. The super short description is the OGL caused a large number of RPG's to be developed using the system, and the overabundance was a big part of why it fell out of favor. Wizards also created d20 Modern, which is the d20 system with laser guns. And of course, people got pissed at WotC when they made all sorts of changes to the OGL.
So if the d20 system fell out of favor, are we still using it today, and why? We are, but the d20 system has undergone several changes since the introduction of the system. The core basics remain the same, but the 5th edition streamlined the rules more than ever. No more worries about getting a +1 when you do that, or a +3 if you attempt this. Now you roll at advantage or disadvantage, making the number of modifiers you need to worry about much fewer, and your ability to roll more dice higher. Does it make for a more accessible game to play? Sure does. Does that make the game easy, almost boring? It depends on who you ask. New folks to the game are introduced to a friendly system, making it easy to learn, and in turn, they will continue to play, bring their friends into the fold, and expand the popularity of the game. For some, especially the old grognards, the game has become dull and stale. Being one of those older people who are still playing the game, I would argue that the game hasn't become stale at all people aren't looking in the right places. Sure the core mechanic of the game has been slimmed down, but that only speeds up the game, which in turn leads to more time playing the game versus trying to figure out the math. There's still plenty to keep track; whether your movement has been slowed, your AC was buffed via a spell, or you can use a modifier die thanks to bardic inspiration. The game has evolved, and the beauty of it is, if you don't like evolution, you can still play 1e and bury yourself under the warmth a million charts.
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