A role system for resolving battles and wars in fantasy settings, with optional PC integration.
INTRODUCTION
The d20 War-Mode System is a simplified combat framework designed to resolve large-scale battles and wars while preserving the tone and tactics of D&D 5e.
It abstracts creatures, heroes, and armies into streamlined ratings—Offense, Defense, Magic, and Steps—allowing quick yet faithful outcomes.
Unlike traditional wargames, War-Mode keeps the fantasy motif alive: giants hurl boulders, wizards rain fire, clerics hold the line, and player characters can meaningfully sway the tide of battle without rolling hundreds of dice.
CORE CONCEPTS
Each unit—whether a squad of soldiers, a band of orcs, a giant, or a dragon—has six attributes rated from 0 to 20 (similar to ability modifiers on a d20 scale).
These numbers replace attack rolls, AC, saving throws, and DCs.
Meaning
Typical Range
Melee Offense (MO)
Attack power in close combat
4–20
Ranged Offense (RO)
Accuracy and impact at range
2–18
Physical Defense (PD)
Armor, agility, toughness
4–20
Magical Offense (MgO)
Spellcasting, breath weapons, divine smite
0–20
Magical Defense (MgD)
Magical resilience, saving throws
4–20
Steps (Durability)
Structural integrity, morale, or HP abstraction
3–10
Movement
Each unit’s movement rate is measured in 50-yard increments per battle turn (30 seconds). • 30 ft speed = 1 Move • 40 ft = 1.5 Move • 50 ft = 2 Move • Mounted +1.5 Move • Tags like Fly X, Climb +1, Swim +1 modify movement by terrain type.
ROLLING COMBAT
All combat uses one roll per attack. The Margin of Success (MOS) determines damage.
1. Choose attack type (Melee, Ranged, or Magical).
2. Roll: d20 + Offense vs 10 + Defense.
3. Subtract to find MOS.
4. Convert MOS to Steps lost:
Margin of Success
Steps Lost
Result
< 0
0
Miss
0–4
1
Light hit / casualties
5–9
2
Solid strike / heavy casualties
10+
3
Devastating blow / rout risk
When a unit loses all its Steps, it is destroyed or scattered.
Losing 2+ Steps in a turn can also trigger a Morale check.
MORALE
Units check Morale whenever they:
Lose 2 or more Steps in one turn, or Their side falls below 50% total Steps remaining.
Roll: d20 + Quality vs 12 + Steps lost this turn
Unit Quality
Bonus
Militia
+2
Trained
+4
Veteran
+6
Elite
+8
Monstrous / Legendary
+10
Fail → Fall Back (disengage, regroup)
Fail by 5+ → Rout (flee or are removed from battle)
COVER & FORTIFICATIONS
Cover affects both PD and MgD equally when applicable.
Cover Type
Defense Bonus
Notes
Light (25%)
+2
Bushes, fences, wagons
Moderate (50%)
+4
Barricades, palisades
Heavy (75%)
+6
Stone walls, parapets
Full
Impassable
Wall of Force, cliff face
Stockade or Stakes: +4 PD front arc; Large/charging attackers −2 Offense. Earthwork / Parapet: +6 PD; ranged attacks limited to 1 Step max. Stone Wall or Keep Gate: PD 18, Steps 6; breached when reduced to 0.
SPECIAL TAGS
These traits modify specific rolls or situations.
Tag
Effect
Leader / Standard
+2 Offense (melee or ranged) to allies within ~50 yards.
Pack Tactics
+1 Offense when two or more allied units engage the same target.
Shield Wall
+1 PD when adjacent to allied unit in formation.
Brace vs Large+
+2 Offense when holding against a charge from a Large+ enemy.
Flank / Rear
+2 Offense when attacking a target engaged on multiple sides.
Evasion
+2 effective MgD vs AoE; MOS 0–4 causes 0 Steps.
Medic / Cleric
Prevent 1 Step of losses per turn across nearby units; +2 Quality on Morale.
Flight / Climb / Swim
Grants movement type and bypasses certain obstacles.
RESISTANCES, IMMUNITIES, AND VULNERABILITIES
This system handles energy types and damage immunities simply and consistently.
Condition
Adjustment
Example
Resistant (Type)
+4 Defense vs that damage type
Fire Elemental vs Fireball
Immune (Type)
No effect from that damage type
Frost Giant vs Cone of Cold
Vulnerable (Type)
−4 Defense or +1 Step when hit
Troll vs Fire
SPELLS AND EFFECTS
Treat spells as templates with one of the following effects:
Blasts & Breaths:
Use MgO vs MgD for each target in the area. Apply resistances/immunities as above.
Walls:
Wall of Force — impassable; blocks line of effect; grants +4 PD/MgD behind it. Wall of Fire — creates a hazard template; crossing or starting in it inflicts one MgO roll per turn.
Control (Fog, Darkness, Fear):
Fog/Darkness → ranged attacks −4 Offense if firing through/into. Fear → immediate Morale check. Slow → target −2 Offense, half movement.
Buffs:
Bless, Haste, Heroism → +1–2 Offense or +2 Quality (morale) to up to three units.
Debuffs:
Bane, Bestow Curse → −2 Offense or −2 Quality to 1–2 units.
Healing / Medics:
Each cleric prevents 1 Step of losses per turn across adjacent allies.
Concentration:
If the caster loses 2+ Steps in a turn, make a check:
d20 + level bonus vs 12 + Steps lost. Fail = spell ends.
DERIVING VALUES FROM THE MONSTER MANUAL
You can create war-mode stats for any creature in 60 seconds.
Step 1: Determine CR → √CR = r
Step 2: Use these formulas:
MO = clamp(4 + 4r, 2, 20) PD = clamp(4 + 3.5r, 2, 20) MgO = 0 if CR < 3, else clamp(4 + 3.8r, 2, 20) MgD = clamp(4 + 3.5r, 2, 20) Steps = max(3, 2 + round(r)) RO = MO − 2 (if real ranged) or MO/2 (if harassing)
Step 3: Adjust ±1–3 for:
High attack bonus (+11 or higher) → +1 Offense High AC (18–20) → +1–2 PD Magic Resistance / Legendary Resistance → +2 MgD AoE breath or Fireball-tier spell → ensure MgO ≥ 12 Vulnerabilities or poor defense → −1–2 PD/MgD
Step 4: Add Tags (flight, reach, pack tactics, etc.)
DERIVING VALUES FROM PLAYER LEVEL OR HIT DICE
Use this table to convert NPCs, classed characters, or troops by level or HD.
Level or HD
Melee Offense
Physical Defense
Magical Offense
Magical Defense
Steps
Notes
1
6
6
0
6
3
Basic militia
2
7
6
2
7
3
Trained unit
3
8
7
3
8
3
Veteran squad
4–5
9–10
8–9
4–5
8–9
3–4
Capable soldiers
6–8
11–13
9–10
6–8
10–11
4
Elite
9–12
14–16
12–13
10–15
12–14
4–5
Heroes / commanders
13–16
17–18
14–16
15–18
14–16
5
High heroes
17–20
19–20
17–18
18–20
17–18
5
Legends / paragons
Use Hit Dice instead of level for monsters or NPCs without CR:
Treat each 2 HD ≈ 1 level for this conversion. A 6 HD creature ≈ level 3; a 12 HD creature ≈ level 6.
UNIVERSAL BENCHMARKS
Use these for sanity checking.
Category
Example
MO
PD
MgO
MgD
Steps
Goblin (CR 1/4)
Weak skirmisher
3
3
0
3
3
Orc (CR 1)
Basic troop
6
4
0
3
3
Veteran Pikeman (level 3)
Human elite
8
7
0
8
3
Ogre (CR 2)
Heavy brute
10
8
0
4
3
Hill Giant (CR 5)
Massive shock unit
16
14
0
6
6
Cloud Giant (CR 9)
Elite brute
18
16
8
12
7
Storm Giant (CR 13)
Legendary elite
20
18
14
14
8
Adult Dragon (CR 15)
Apex threat
20
18
18
16
9
Titan (CR 22)
Demi-god
20
20
18
18
9
BUILDING BATTLES
Use these quick force ratios:
Infantry vs Hill Giants: 40–50 disciplined infantry per giant (pikes + leader). Add 1 mage per 40–50 and 1 cleric per 30–40 for sustainability. Cavalry vs Fire Giants: 6–7 heavy cavalry per giant with charge, leader, and flank bonuses. Dragon Assault: 2 heavy ballistae + 1 mid-tier wizard + 100 veteran troops can repel a single adult dragon. Defensive Fort: Infantry behind 50–75% cover can survive 2–3 times longer against ranged or magical assault.
DESIGNER DIALS
To fit your table’s tone:
Monsters tougher? +1–2 Steps. Shorter battles? Auto-rout at 60% Steps lost. Bloodier? Add a “MOS 15+ → 4 Steps” tier. Low-magic campaign? −2 MgO globally. High-fantasy war? Allow heroes to reroll failed Morale once per battle.
WORKED EXAMPLE: FIREBALL VS OGRES
Wizard (Level 9): MgO 15
Ogre: MgD 4, Steps 3
Roll: d20 + 15 vs 14
Average result (10.5 + 15 = 25.5) → MOS ≈ 11.5 → 3 Steps each.
Each ogre in the blast is destroyed outright.
If resistant (e.g., Fire Resistance), +4 MgD → 18; MOS ≈ 7.5 → 2 Steps (wounded, not destroyed).
WORKED EXAMPLE: CLOUD GIANT VS FORTIFIED PIKES
Cloud Giant (MO 18) vs Veteran Pikes (PD 10 +6 for parapet = 16)
Roll: d20 + 18 vs 26 → need 8+. Average MOS ~2 → 1 Step (glancing).
Pikes with Brace (+2) strike back: MO 10 vs PD 16 → MOS ~0–4 → 1 Step on a hit.
The wall holds for multiple turns; siege equipment or spells are needed.
SUMMARY CHECKLIST
Roll once per attack: d20 + Offense vs 10 + Defense. Margin of Success → Steps (0/1/2/3). Morale at 2+ Steps lost or 50% casualties. Apply terrain: +2/+4/+6 for 25/50/75% cover. Resistances: +4 Defense; Immunity: no effect; Vulnerability: −4 or +1 Step. PCs use simplified war stats by level. You can derive any monster instantly from CR or HD. Keep it cinematic—each roll represents a wave of violence, not a single strike.
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