Strategic Mass Combat
The Player’s Handbook combat rules are designed to model small fights with less than twenty combatants. These rules provide a framework to extend D&D combat to model larger-scale conflict with dozens or hundreds of soldiers on either side, while still leaving room for individuals to turn the tide of battle.
Rolling Large
These rules scale up many things in combat. Hit points represent not just an individual's mettle and health, but casualties and fatalities amongst a numerous cohort. An attack roll is not just a single swing, but a massed attack from twenty allies. Distances are abstracted even further than normal, and dozens or hundreds of creatures act at once.
Scale
These rules assume the use of a grid with miniatures or tokens. Each round of combat represents six seconds, as normal. Distance, however, is scaled differently:
Squares. A single square measures 30 feet on each side.
Diagonals. Squares that only touch at a corner (touch diagonally) are not considered adjacent; each is 1 square away from the other.
Ranges. The normal rules for ranges apply, simply on a coarser grid, with the exception that a range of less than 30 feet can reach into an adjacent square.
The Combatants
Under these rules, an army has two kinds of elements:
- Units, which each represent twenty creatures of the same kind, and act as a single entity.
- Commanders, which are the important individuals, such as adventurers or generals, who act alone.
Units
A unit consists of twenty identical creatures that move and fight as a single entity. A unit of creatures occupies the same space on a 30-foot grid as a single one of those creatures would on a 5-foot grid.
| Creature Size | Space |
|---|---|
| Medium or smaller | 1 square |
| Large | 2 × 2 squares |
| Huge | 3 × 3 squares |
| Gargantuan | 4 × 4 squares |
Statistics
A unit has identical statistics and abilities to a single one of the creatures it represents, such as Armor Class, hit points, attacks, and so on, except for the following changes:
Falling to 0 Hit Points. Units don’t make death saving throws and are eliminated if they reach 0 hit points.
Reach. Unit melee attacks can reach targets in adjacent squares. If a unit takes the Attack action with a melee attack that has a reach longer than the size of the individual creature, it can make another such attack as a bonus action.
Speed. The speed of a unit is equal to the speed of the individual creature. Moving one square costs 30 feet of movement, with the exception that creatures with a speed above 0 and below 30 feet can use all their movement to move 1 square, which can be into difficult terrain if they took the Dash action this turn.
Commanders
A commander is a significant single creature on the battlefield, usually a player character or a powerful NPC or monster. Each side in a mass combat will nearly always start with at least one commander.
A commander has the following characteristics:
- It occupies one square, regardless of the creature’s size.
- It can move through and end its turn in allies’ space at no extra cost.
- It can give orders (see orders, below).
Because of the difference in number and scale, whenever a commander interacts with a unit:
- The commander has disadvantage on attack rolls and saving throws.
- Attack rolls against it have advantage.
- Damage it deals is halved and damage it takes is doubled, with the exception of large area effects (see area effects, below).
- It can’t apply conditions or any other non-damage effect to units, with the exception of through large area effects.
Combat Procedure
Mass combat is much like normal combat, except that the commanders control the flow of battle through giving orders.
In a normal round, commanders act on their own initiative and give orders to their units. Units act as soon as they are ordered to, and can only receive one set of orders in a round. At the end of the round, units that haven’t received orders this round take a default action based on their situation.
Initiative
Each commander rolls for initiative normally. Units don’t roll for initiative; they act when their commanders order them to, or at the end of the round otherwise.
Rounds
Mass combat is organised into discrete rounds, from the highest initiative count to the lowest. Units that have not received orders in a given round act after the lowest initiative among combatants.
Commanders and units can be surprised as normal. Surprised units don’t act in the first turn they normally would and can’t take a reaction until that turn ends.
Commander Turns
Commanders take their turns as they normally would. They can attack and interact with units and other commanders.
Orders
Commanders have a special action they can take: the Give Orders action.
They can take this action when they are adjacent to or in the same space as an allied unit. They order that unit and any number of contiguous units they choose (units adjacent to the first one, and units adjacent to those, and so on) to take a turn to do a certain set of things.
Decide what actions the units will take, what their targets will be, and how they will move. Units can take any action that would be available to the individual creature they are composed of. The same action is chosen for all the units ordered, though they may have different targets and paths chosen. Units can’t break up their movement, but otherwise have a normal turn, including taking a bonus action if one is available and/or interacting with an object, all of which is decided during the order.
After giving orders, the commander continues their turn.
Unit Turns
Immediately after a commander’s turn, if that commander gave orders during their turn, the units that were given those orders take a shared turn to execute those orders.
The units act simultaneously. Execute the first action or movement in the orders, then the next, and so on. Resolve each in its entirety, including any reactions taken by any combatants, before moving on to the next part of the turn.
A unit that has been given orders can’t receive new orders in the same round.
Invalid Orders
If an action or move is invalid by the time a unit reaches it, the unit does as much as it can, but doesn’t change any targets or paths. Units ignore any part of an order that they are completely unable to execute.
Reactions
Units take reactions individually. The turn in which they act counts as their turn for reactions and other effects. Whenever a unit can take a reaction, it does.
An Example of an Order
A commander orders a set of units to move and then attack, choosing paths and targets as he does so. He proceeds to use his own movement and ends his turn.
During the turn for those units, they will first all move as ordered, then all attack the targets the commander chose. None of them can move after attacking, nor attack before another unit in the turn moves, nor switch the target of their attack after another unit in the turn hits or misses. All the choices are made when orders are given.
Units Without Orders
At the end of the round, after all other combatants have acted, units that have not received orders this round act based on their situation.
Unordered units take the first course of action that applies to them out of the following:
- Break. If they're at 5 HP or less, they take the Dash action and move, seeking a safe path away from enemies.
- Skirmish. If they're adjacent to an enemy, they take the Attack or Multiattack action to make melee attacks, and don't move.
- Regroup. If they're not connected to an allied commander that they're aware of by contiguous allied units, they take the Dash action and move towards the nearest allied unit that is so connected.
- Continue. Otherwise, they attempt to continue or repeat their most recent orders, standing idle if their orders are explicitly completed or if they have none.
Group unordered units by which of the four above courses of action they take. Starting with Break, resolve the turns of the units taking that course and any relevant reactions, before moving on to Skirmish, and so on.
If more than one side in the combat has unordered units taking the same course of action, group and resolve them in order based on their dexterity modifiers, from highest to lowest, breaking ties randomly.
Area Effects
Spells and other abilities that affect more than one target creature act differently depending on whether their extent is less than a single square, or equal to or more than a single square.
Small Areas
A small area effect is one with an extent of less than one square. Cones and cubes of less than 30 feet in size, and spheres and cylinders of less than 15 feet radius are examples.
This category also includes effects with a fixed number of targets from two to nineteen.
Units
A unit targeted by a small area effect is affected as if it were the primary target, and as if it were one secondary target as well. In most cases, this will mean saving throws are made twice and/or damage is taken twice.
Commanders
A commander using a small area effect on a unit or targeted by one from a unit is subject to the normal commander penalties of dealing half damage and taking double damage.
A commander in a willing unit’s space can affect that unit with a small area effect as if it were a large area effect if the area is at least three times wider than the space an individual creature in that unit would occupy. Essentially, a unit can 'cluster around' a commander to best utilize such an effect.
Lines
Long lines narrower than 30 feet but at least 60 feet long and other similar shapes may affect multiple squares, but still apply to each of them as a small area effect.
Large Areas
A large area effect is one with an extent equal to or greater than one square. Cones and cubes of 30 feet or more in size, and spheres and cylinders of 15 feet or more in radius are examples.
To evaluate which squares are included in such an area, choose a corner or center of a square as the point of origin of the effect, then follow its rules as normal. If the area covers at least half a square, it affects that square.
This category also includes effects with twenty or more discrete targets.
Units
Units should almost never be able to use large area effects. When they do, treat those effects as twenty simultaneous and independent effects, targeted at the same locations or different ones.
Commanders
Commanders suffer no penalties when using or targeted by large area effects. Using large area effects enables commanders to have a massive impact on the battlefield, affecting one or more full units at a time.
Terrain
Rubble, forests, and water are examples of terrain that can substantially alter the battlefield. The DM designates areas of significant terrain, which will usually have an effect on units and commanders occupying squares in those areas.
- Forest areas provide half cover and heavy obscurement to occupants, and are difficult terrain.
- Defensive fortifications provide half, three quarters, or full cover to their occupants, depending on their construction. Units cannot cross walls without climbing, breaking, or otherwise bypassing them.
- Shallow water, between knee- and waist-deep, is difficult terrain and attacks against units in shallow water have advantage.
- Deep water can only be occupied by units and commanders that have a swim speed.
- High ground, if particularly defensible against its surroundings, grants advantage on melee weapon attacks by occupants.
Other simple obstacles, like loose sand, deep snow, or thick mud, are difficult terrain. In most cases, creatures with a speed of 55 feet or less can't enter a square of difficult terrain unless they take the Dash action.
Appendix I: Optional Rules
Solos
Some large battles contain individuals that have a substantial effect on their own but aren’t an authority over any troops. For those individuals, simply use the commander rules, but remove the ability to give orders, and the DM decides whether or not unordered units treat them as a commander when they Regroup.
These powerful individuals, called solos, will still interact on the correct scale with the units around them, but are no longer tightly linked to their allied troops. This is appropriate for spellcasters, giant monsters, and so on. You can also use this rule for player characters if they are participating in a battle but not in a position of authority.
Siege Weapons
Siege weapons are treated as solos, but they don’t have a turn in the initiative order. Instead, a unit that shares a space with one or more siege weapons can use its action to operate them.
When a unit takes this action, it can either:
- Move any siege weapons sharing a space with the unit along with the unit’s movement later this turn; or
- Load, aim, and fire any number of such siege weapons as if the unit had twenty actions with which to do so.
No siege engine may be loaded twice, aimed twice, or fired twice this way in a single turn.
Ending the Battle
The encounter continues until the fighting stops. Most commanders will not continue a lost battle to the point of total elimination, instead opting to retreat, surrender, or otherwise cease fighting.
Each side entering a battle goes in with a goal in mind, whether that goal be simply killing as many of the enemy as possible, or some particular objective that the opposing force happens to be an obstacle for. If you can’t think of any, consider why that side is engaging in costly battle at all.
If you need a concrete way to decide when a side gives in, use these goals and objectives to define victory conditions for the fight.
Victory Conditions
A victory condition is any situation that, once achieved, will cause one or more sides in a battle to no longer have a reason to keep fighting. This is usually because one or both sides can no longer make progress towards their goal, either because they have achieved it, it is impossible, or continuing would be too costly.
Victory conditions can include:
- The destruction of an important structure such as a bridge.
- A side achieving a defensible position that another cannot effectively assail.
- A force successfully crossing a chokepoint.
- The elimination of certain important commanders or units.
- The acquisition and extraction of an object or resource, such as a siege engine.
Determine which victory conditions are possible before a battle begins. When one of them is achieved, determine which sides, if any, no longer have a goal they can effectively fight for. The commanders of those sides, when they recognize the situation, will try to retreat or surrender unless both of those options are untenable.
If a losing side does fight to its last member, consider stopping the encounter early and narrating the remaining combat, to reduce how much time is spent on the encounter after the outcome is aready decided.
Calculating Casualties
A unit being eliminated doesn’t mean its members are all dead, just that it is sufficiently disabled physically or psychologically to no longer function on the battlefield. After fighting ceases, if allies have time to safely access the battlefield, survivors can be recovered.
Able Survivors. For each eliminated unit, roll a d10. The total is the number of able survivors, who can recover to fighting condition in 10 days of rest without travel if food, water, and medical help is available.
Permanent Casualties. For each eliminated unit, roll another d10. The total is the number of alive but permanently disabled casualties. Some of these are physically disabled, while others are victims of the psychological consequences of war.
Hits-to-Drop Instead of Hit Points
In particularly large battles, it can get harder to manage the dice efficiently. To aid this, one can replace the Hit Points of each unit with hits-to-drop.
Divide the hit points of each unit by the average damage dealt by the most common attack amongst that unit’s enemies, and round up to find that unit’s hits-to-drop. Mark this number with a die on or in place of that unit’s miniature or token.
Whenever a unit takes a hit, rather than roll damage, simply reduce the hits-to-drop by one (or two for a critical hit). For unusually strong attacks, such as from a siege engine, subtract two or more points instead proportional to how much more damage those attacks deal. At 0 hits-to-drop, a unit is eliminated.
Lastly, units at 1 hit-to-drop, rather than 5 hit points or less, will Break if lacking orders.
Uniquely Scaled Units
There’s no reason five or so powerful creatures can’t be represented by a unit. Simply divide the hit points of the creature by the appropriate factor (in this case, four), and do the same for damage. Five is about the lower limit where the advantages of being a unit are maintained; below that, use one or more commanders instead.
The reverse can be done to represent more than twenty creatures with a single unit, which is useful for particularly small or weak creatures.
Initiative. You can also place such a unit in the initiative order like a commander. If you do, it can’t receive orders, but the DM may allow it to give orders if it is in a position of authority.
Alternate Actions for Unordered Units
The list of courses of action under Unordered Units (see above) applies to most intelligent units, but should be modified for units that usually act in a very different way.
The simplest way to do this is to remove actions from the list. For example, religious zealots may never Break, even when near death.
You can also change the order of the existing actions. For example, independent scouts may Continue their last orders even when disconnected from a commander, only choosing to Regroup if their orders are complete.
You can also replace the whole list with one or more new actions. For example, mindless undead will always walk towards and try to attack the nearest living creature they can see unless magically ordered otherwise.
Special Weapons
The rules for attacks with a long reach represent how units with such attacks can bring more of their weapons to bear at a time. If a more accurate simulation of special weapons is wanted, use these rules.
Lances. Lances are most useful during the initial charge, becoming less useful as the melee develops.
Attacks with lances are at disadvantage unless the wielder entered reach with their target earlier on the same turn. This replaces the Special property of the lance.
Siege Weapons. Body armor is normally ineffective against heavy projectiles such as rocks from a mangonel or trebuchet.
To reflect this, replace the attack roll from such a weapon with the target making a Dexterity saving throw with a DC of 10 plus the attack bonus of the siege weapon, taking the damage on a failed save.
Awareness
Usually, it's okay to assume that units are aware of all friendly commanders that have not taken the Hide action. To introduce communication as a complication, limit commanders to only giving orders to units that can see or hear them.
Line of Sight. Units of a given size category obscure commanders of the same size category that are behind or in the same space as them. For example, a human general on foot can't be seen behind human footsoldiers, but that general on a horse can.
Hearing. A creature can shout to be heard over battle noise within 90 feet. War horns, drums, and similar instruments can be heard within 1 mile.
Playing on Hexes
If the battle is run using a hex grid rather than a square grid, the rules for opportunity attacks should be changed to retain the character of engagement and disengagement.
When playing on a hex grid, units and commanders provoke opportunity attacks from an enemy whenever they move from a hex within that enemy's reach, even if they're moving to another hex within that reach.
Appendix II: Player Options
Feats
A DM can allow players to take these feats in a campaign that focuses on mass combat, to help meet the demands of such a a campaign that aren't present in a traditional adventure.
These feats can help distiguish the styles of different commanders and ensure that players feel like their characters are uniquely capable in a mass battle context.
Frontline Commander
You excel in leading troops right from the thick of the fray. When you’re a commander, you gain the following benefits:
- When you share a space with an allied unit, your AC is always at least equal to theirs.
- You can take the Give Orders action as a bonus action instead.
- Whenever a unit you are sharing a space with moves, you can use your reaction to move along with it to its new location.
Figurehead General
You are adept at managing and inspiring the troops around you. When you’re a commander, you gain the following benefits:
- You can Give Orders to a unit and its contiguities at a distance of sixty feet.
- Allied units Regrouping toward you don’t provoke opportunity attacks.
- Allied units that can see you never Break.
Lone Champion
You have learned how to best fight when enemies abound. When you’re a commander or a solo, you gain the following benefits:
- Damage units deal to you isn’t doubled.
- You don’t provoke opportunity attacks from units.
- You can enter the space of a hostile unit. Their presence does not cause their space to be difficult terrain for you. Additionally, being a commander or solo doesn't grant you disadvantage on attacks against them while you’re in their space.