A simple, Risk-inspired, mass battle system for D&D-type games
For the final climactic battle scene in a D&D 5e campaign that concluded late last summer, I wanted a simple mass battle system that would make the PCs' actions count, but that also would also include elements of randomness.
It was a Pelennor Fields-type scenario, with a big army of bad buys attacking a walled city with a smaller number of defenders.
The broader arc of the campaign as a whole had acquired a structure similar to that of the story in the video game Dragon Age: Origins, wherein the protagonists endeavour to build a coalition to oppose evil. In this case, the PCs had undertaken various quests to earn the friendship of a city of Dwarves, of the Elves of a particular forest, and of another human kingdom in addition to the trust of the city's inhabitants. I wanted their successes to matter, mechanically, in the final battle where all these allies would show up and fight together.
But I also wanted to keep things simple and not have to deal with the endless series of circumstantial modifiers and general complexity that plague most mass combat rules. (I had already rejected various TSR-era and recent WotC mass combat systems for that very reason.) At the same time, I wanted something more elaborate than a single die roll.
I wanted to PCs to continue to be able to shape the circumstances of the final battle up to the last moment, as well as play a role in the battle itself. While I was fine handling some pre-battle action using the normal D&D roleplaying systems, I didn't want the resolution of the final battle to get bogged down in the details of a standard D&D combat. The latter typically lasts seconds or minutes in game time, but tens of minutes or even hours in real time.
The solution was Risk--with a few elements inspired by the mass combat rules in Savage Worlds. The opposing forces are represented by pools of tokens, as in Risk. One side is attacking and the other defends. As anyone who has played the board game knows, the attacker should enjoy a significant numerical advantage if they plan on winning because the dice-rolling system holds built-in advantages for the defender. This handily modeled the underdog situation of the heroes and their allies. But the key about Risk is that when dealing with sizeable armies, the system breaks the battle down into stages by placing limits on the number of tokens that can be risked with each dice roll. Things can see-saw back and forth dramatically rather than being over in a single cast. And by tweaking the Risk system to create opportunities for the players to gain further mechanical advantages, it serves to model the classic trope of heroes succeeding against overwhelming odds.
Prior to the battle proper, the PCs had a chance to collectively do one thing to alter the course of events, which we would play out using the usual game systems. Mechanically speaking, the objective was to reduce the strength of the opposing force by lowering its Hit Dice total. At one level, it meant a choice between trying to take out large numbers of low-Hit Dice creatures or one or two "boss"-type creatures. At another level, there were in-world strategic factors to consider. There were three obvious threats: the huge army of gargun (goblinoids) approaching the walls; some black-sailed airships, and a kraken. The PCs chose to deal with the kraken. (A wise choice, since its ability to bring down the city's walls would have made the gargun army that much more formidable and exposed the innocent non-combatants to danger.) After several rounds of normal combat (if you can call fighting a kraken "normal"), the PCs eliminated that threat through a combination of enchantment and physical attacks, driving the sea monster away. In fact, they did it so easily that I felt no guilt whatsoever about then revealing a kaiju-sized automaton that was the bad guys' secret weapon. This enemy was a bit tougher, but they managed to win out.
When they were done, I quickly determined the relative strengths of the two sides, and we proceeded with the final battle, Risk-style. (I had previously set up a spreadsheet to do this. The spreadsheet wasn't absolutely necessary, but was helpful to quickly re-calculate the relative strengths of the armies. One could just as easily come up with a determination on the fly.) In this new phase of action, the PCs could still act, but according to the mass battles rules below, which gave them a chance to affect the outcome of the Risk-combat while exposing them to some danger in the form of lost hit points.
Despite eliminating the kraken and the colossus as threats, the enemy forces still outnumbered the defenders, but during the mass combat the PCs were able to earn a number of re-rolls that decisively turned the tide. (In normal Risk, of course, no one gets to re-roll anything.) In real time, the entire affair lasted one and a quarter sessions -- a bit over 3 hours of time at the table. (Or, in our case, at our computers, since we were social distancing by necessity.) Most of that time was spent resolving two fights (kraken and automaton) that lasted only a minute in the game world -- such is the reality of D&D 5e with 20th-level PCs. It's slow-ish to run. But in the second phase, the ensuing struggle on the battlefield representing several hours of desperate back-and-forth, was resolved very quickly with fewer than a dozen Risk rolls. PC actions in each round of the mass battle could be narrated as a montage of slow-motion sequences that suitably represented their efforts.
I felt it was, overall, a satisfying pacing that combined in a meaningful way (1) the long-term consequences of the PCs' efforts over a five-year campaign to cobble together a coalition; (2) the players' mastery of their PCs' individual abilities, deployed according to the game's normal systems; and (3) the uncertainty and peril of a massive battle whose outcome the PCs could shape but not dictate. The d6 Risk rolls during the mass combat segment were full of genuine suspense for us. They could have lost.
Here are those rules--well, guidelines really--for your perusal, commentary, and perhaps even enjoyment.
Simple Mass Battle System
Setup
Determine the total strength of each side. (In
D&D, the easiest way of doing this is to add up the number of character
levels or Hit Dice in each army.) Give the force with the larger total 10
tokens and the other force a proportionate number of tokens. Don’t forget about
mounts, animal companions, etc.
Decide which side is attacking and which
side is defending.
Example: Five 8th-level PCs join
the city guard to defend against an attack by giants. The guard (most of whom
are 1st-level fighters) and their officers have 447 levels among them
and the PCs an additional 40, for a total of 487. The 52 attacking giants (a combined force of
Hill, Frost, and Stone Giants) represent a total of 571 levels. The giants have
10 tokens, the defenders 9. (Those aren't good odds for an attacker in Risk.)
Combat
Play Risk.[1]
The following sequence represents one round of battle.
1. The attacker announces the number of dice they wish to roll: 1, 2, or 3. The attacker must have at least one more token in their[2] army than the number of dice to be rolled. E.g., the attacker must have at least 4 tokens to roll 3 dice.
2.
The defender will roll either 1
or 2 dice. They must announce their decision before rolling. To roll 2 dice,
the defender must have at least two tokens.
3.
Attacker and defender roll dice
simultaneously.
4.
Compare the highest die each
side rolled. If the attacker’s is higher, the defender loses one token. But if
the defender’s is higher, the attacker loses one token. In the case of a tie,
the defender wins.
5.
If both combatants rolled more
than one die, compare the next-highest dice in each pool and repeat the process.
If the attacker has at least two tokens
remaining, they may decide to attack again. If they choose to pause and regroup
or withdraw, the defender may decide to counterattack, in which case they
become the attacker during the next round of combat.
Lost tokens represent fighters that are
killed, wounded, or routed. There is no need for a separate system to check
morale; any remaining tokens are assumed to be combat-ready.
Note: because the defender never rolls more
than 2 dice, the attacker can never lose more than 2 tokens on a single roll. For
the same reason, the defender can never lose more than 2 tokens in a single
round of battle.
PCs during the battle
Have PCs outline how they will contribute
to the current round of battle and then make an appropriate ability check: STR
for attacking in melee, DEX for archery, spellcasting ability for magic, INT
for a pursuing a tactical advantage, CHA for inspiring troops, etc. (Note: this
is NOT a skill check—this roll abstractly represents a protracted series of
actions of various kinds, not a single action or use of a specific ability or spell. Choose the dominant
ability related to whatever the PC wishes to do.)
Make an appropriate test according to whatever
D&D system you use. The difficulty should be modified by the relative sizes
of the opposing forces. For example, in 5th ed., the target number
or DC could be 10 plus the number of tokens representing the enemy force. In B/X, a PC
rolls under the relevant ability score, which could be adjusted up or down
depending on the difference between each side’s number of remaining tokens.
Failure means the PC suffers bad fortune on
the battlefield and loses 2d4x10 % of their maximum hp. (This could reduce a previously wounded PC’s
hit points to zero, meaning they have fallen on the field of battle.) Success
means the PC suffers 2d6 hp damage and their side is granted a re-roll of any
one die during the next round of mass combat.[3]
This is a huge advantage in Risk, and should motivate the PCs to act
each round, even if it imperils them as individuals!
Aftermath
If the defender runs out of tokens, it
means their forces are dead, wounded, or routed (see below for survivors). The
attacker can occupy their position and pillage their gear, etc. If the attacker
is reduced to a single token, they can no longer attack and may be vulnerable
to a counterattack.
When one side runs out of tokens, it’s
defeated: that side’s combatants are wounded, dead, or fleeing. If it’s
important, determine the survivors by rolling 1d6 for each token lost during
the battle. On a 1 or 2, that token is lost forever; on a 3-6, the token
represents survivors, included wounded combatants and routed and leaderless
units. Compare the surviving post-combat tokens to the pre-combat figure to
determine how many levels/Hit Dice worth of combatants perished during the
fight and distribute losses accordingly. Whatever the result, the surviving
tokens will not be able to form a cohesive army for a considerable time.
[1] See full rules at https://www.hasbro.com/common/instruct/risk.pdf.
[2] ‘Their’ is used here as a gender-neutral singular pronoun.
[3] This section, along with the idea of ten tokens for the larger force, was inspired by Savage
Worlds Deluxe Explorer’s Edition, pp. 106–107.
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