D&D started as a hack on a war game, which is why OD&D depends on, but does not provide, mass combat rules. The original game included kingdom management rules and prices for castles and armies. The first adventure module, in the Blackmoor supplement, had rooms that contained hundreds of soldiers. You were expected to break out TSR’s Chainmail war game to use these things. In fact, as you got higher and higher level, Gygax expected that more and more of your time playing D&D would actually be spent playing Chainmail. That’s sort of like if you went to a Scrabble tournament and they said, “Good news! You guys are such good Scrabble players that now you get to play Monopoly.”
D&D went mainstream because audiences liked the fast, immersive, co-op game of the imagination, and they didn’t latch onto (or even understand the references to) the slow, rules-bound, head-to-head, miniature-requiring war game. So, in later editions, the Chainmail references were cut. Essentially, D&D’s intended end game, conquest and rulership, was removed. The middle of the game, grinding for money, was extended, even though there were now no castles and armies to spend the money on.
And this is a big loss for D&D. In any edition, high level D&D is not a solid product. High level fights are swingy, monster variety is sparse. And, worse, with epic battles and kingdom-building mostly offscreen, characters can’t leave their mark on the game world, except by saving it from ever more powerful dungeon monsters. Players and DMs alike generally try to keep away from war epics, because running big battles isn’t something D&D does.
To fill the hole left by the removal of Chainmail and epic-fantasy play, TSR and WOTC churned out stand-alone battle supplements every few years:
-OD&D introduced Swords & Spells, which was an updated Chainmail with special rules for each of the D&D spells and monsters. It technically allowed battling lone heroes against 10:1 (10 soldiers to a mini) figures, although it recommended avoiding cross-scale combat as much as possible.
-Basic D&D included War Machine: a sort of spreadsheet where you came up with a rating of each army and then rolled a percentile die to decide the battle.
-1e and 2e both published an edition of Battle System. This was another entry in the Chainmail/Swords & Spells tradition, but it came in a box with cut-out-and-assemble peasant houses, which was cool.
-3e had the Miniatures Handbook. Again, its mass combat rules were along the lines of Chainmail, featuring typical war game rules for formations, facing, morale, etc, using d20 mechanics.
-5e has two sets of playtest mass-combat rules, some iteration of which will presumably see official publication some day. The first playtest has traditional wargame-style rules, with frontage, etc. The second boils down every army to a single “battle rating”, in the Basic War Machine tradition.
All of these games perpetuate the flaw that kept Chainmail from catching on in the first place: in order to play them, you have to stop playing D&D.
D&D is not a war game. All the design decisions that make a good war game lead to a bad D&D game, and vice versa.
-Because war games are played competitively, they must be fair. D&D campaigns can only achieve longevity when they are unfair in favor of the players.
-Because war games are fair: war games must have complete rules. You can’t make stuff up halfway through without favoring one of the players. So you can only make a pontoon bridge if there are rules for it. D&D rules are incomplete by design. There are no rules in any edition for making a pontoon bridge, but if you can scrounge up some boats and lumber, the DM will let you do it.
-Because war games are complete: war games must have detailed rules. A good war game models the rock-paper-scissors of archery, cavalry, and spearmen, and provides big bonuses and penalties based on terrain, flanking, morale, fog of war, high ground, and anything else that might conceivably come up. D&D, on the other hand, features abstract combat rules that look nothing like reality. Core D&D combat is a barebones transaction of combatants trading swipes. More important than realism is simplicity, because most of D&D is not in the combat engine but in the DM and player improvisation that happens at the same time.
running an epic battle in D&D
D&D is great at handling small fights – say, five characters fighting a few trolls. Why can’t the same rules handle five characters, the town guard, and a dragon fighting against a skeleton army, a lich, and a dozen trolls?
What if the first edition Monster Manual had contained stat blocks for a skeleton horde, a town watch, and so on? Think of the stories we could have been telling all these years.
My alternate-history army stat blocks are pretty simplistic, but that’s what I like about them. A requirement for war-game standards of rules completeness and detail has been holding back high-level play for years. A D&D combat is great because of all the rules that Gary Gygax didn’t include. Let me talk about the war game rules I think D&D can live without.
Casualties. When half your archers are dead, you can fire half as many arrows, right? Nah. Just as a D&D hero at 1 hp fights at full strength, A 100-soldier army, even at 1 hp, is still a 100-soldier army. After the battle, hit point damage can be translated into some ratio of dead, wounded, and fled, at the DM’s discretion.
Facing, frontage, formation. These rules appear in nearly every war game. We need that level of detail like we need the First Edition grapple rules.
Figure scale. War games are not designed for varying figure scales: every miniature on the battlefield needs to represent, for instance, 20 soldiers. A war-game fight between a lone hero and a 20:1 army unit is usually wonky or impossible. On the other hand, if every army is treated as an individual D&D monster, a tenth-level fighter can battle on fairly even terms with a troop representing 10 first level fighters, which can in turn battle a troll or a unit of 36 goblins.
Time scale. Most war games have realistic but D&D- incompatible turns of ten minutes or more. I’m sticking with D&D combat rounds. If a massive war is over within a few six- second rounds, that’s fine with me.
If anything, D&D-style fights can be too fast. To make it more likely that everyone gets a turn, I’ve added a special rule in my army stat blocks, capping attack damage so that no army can score a one-hit KO. This favors the underdog (and the underdog is usually the PCs). Still, this is a special exception and I wouldn’t be surprised if it were unnecessary.
Leadership bonuses. Many war games assign static bonuses to troops based on the abilities of their commanders. In a war game, which doesn’t allow for referee discretion, this is the best you can do. But in D&D, if a player delivers a speech and leads a charge, or comes up with a clever scheme, the DM can assign appropriate bonuses. The more the players act creatively, the more vivid the scene will be – just as in a standard D&D fight.
Spell rules. We do NOT want a Swords and Spells-style gloss on every spell describing its interaction with armies. Here are my abstractions:
1) Damage spells ignore area of effect. An 8d6 fireball does 8d6 damage.
2) “Condition” spells are all-or-nothing. If a Bless spell can target all the members of an army, it operates normally. Otherwise, it fails.
Morale, flanking, setting ambushes, charging, fighting withdrawal, high ground, and every special case I haven’t already mentioned. First and and Second Edition have explicit morale rules. In other editions, morale failure is by DM fiat. If the local morale rules (or lack thereof) are good enough for 10 goblins at level 1, they’re good enough for 100 goblins at level 10. The same principle, “use existing combat rules”, applies for flanking (present in 3e and 4e), charging (present in every edition but 5e) and so on.
Here are the stat-block templates I’ve used for turning any creature into an army of any size. I’ve done first and fifth editions (my current favorites).
(crossposted/lightly edited from here)