Wednesday, December 15, 2010

Mass Combat Rules - the Easy Way!

Mass combat can be as simple or as complex as you and your players would like to make it. The method used to simplify mass combat is scaling into combat units. Combat is then resolved on a unit-by-unit basis. Thus a battle between two 1000-man armies can be resolved as one battle (scaling the unit to be 1000 soldiers each). Or it can be scaled to two battles involving 500 soldiers in each unit, or 10 battles involving 100 soldiers in each unit, etc. It is all up to the GM and players to decide, based on how much effort they want to put into the overall effort of resolving the mass battle.

For simplicity, combat is resolved on a unit-vs-unit basis using the same mechanics as on an individual-vs-individual basis. It only requires one preparatory step, which is making up the statistics for the battling units.

-- # of fighters - the number of individuals making up the unit
-- total HD - the sum of all the hit dice of the individuals in that unit
-- total HP - the sum of all hit points of the individuals in that unit, usually created by using averages, but can be calculated exactly if specifics are known (consider the average HD to equal 5.5 HP for fighters)
-- average HD - found by calculating the total hit dice divided by the # of fighters
-- average AC - found by calculating the sum of individual armor classes divided by the number of fighters
-- average damage - the average amount of damage caused by the weapons used by the fighters in the unit
-- cohesion level - a percentage score measuring the unit's level of tactical skill and morale, checked when heavy damage is sustained or when attempting a change of battlefield tactics
Cohesion level is base 80, with modifiers as follows: lawful +10, chaotic -10, good +10, evil -10, some peacetime unit drilling +5, extensive peacetime unit drilling +10, long-term/professional peacetime drilling +20, each battle previously fought together as a unit +5; all dwarf + 10; all elf +5; all half-orc -5; all humanoid -10; 50% damage sustained -10; 75% damage sustained -20

Resolving mass combat then involves the following simple steps:

1) The unit attacks using a normal attack table, using the average HD as the fighter's level, against the average AC of the opponent.
2) If the attack is successful, a roll is made from the average damage amount.
3) This damage amount is then raised or lowered by the force multiplier. The force multiplier is calculated from the ratio of the # of fighters in each opposing unit. Thus, if Unit A had 15 fighters vs Unit B which had 10 fighters, the force multiplier for Unit A would be x1.5, from 15/10, and the force multiplier for Unit B would be 0.667, from 10/15.
4) This scaled damage amount is then multiplied by the # of fighters, to determine total damage inflicted that round by the attacking unit.
5) This total damage inflicted is then subtracted from the total HP of the damaged unit.
6) Finally, if heavy damage has been sustained, a cohesion level check is made. These checks are required when a unit sustains 50% of total HP damage and also when a unit sustains 75% of total HP damage. Individual units must also check cohesion when their army as a whole has sustained 50% and 75% casualties.

Example A:
Unit A - twelve first level fighters in chain mail wielding swords, Unit B - ten second level fighters in leather wielding clubs
total HP: A --> 12 x 5.5 = 66; B --> 10 x (5.5x2) = 110
average HD: A -->1; B --> 2
average AC: A --> 6; B --> 8
average damage: A --> 1-8; B --> 1-6
force multiplier: A --> 1.2; B --> 0.833
Each round, the units roll for initiative and roll using the combat tables just as individuals.

Round 1
--Unit A wins initiative, so attacks first, and rolls a successful hit as a first level fighter vs AC 8. Damage is rolled as d8, resulting in a 5. That 5 is then multiplied by 1.2 (their force multiplier) to give 6, then by 12 (the total number of fighters), to produce a total damage of 72.
--Unit B then attacks, a rolls as a 2nd level fighter vs AC 6, also hitting. Damage is rolled as d6, resulting in a 2. That 2 is then multiplied by 0.833 (their force multiplier) to give 1.666, then by 10 (the total number of fighters), to produce a total damage of 17 (rounded to the nearest whole number).

Note: both units get to attack before cohesion checks are made, as the attacks are more or less simultaneous. Unit B has sustained 50% of their total HP as damage, so they must roll a cohesion check. If they fail, they are considered a broken unit, and they would roll on the cohesion failure table. Their cohesion score is calculated, and let us assume they roll under that numbers using d100, so their unit is not broken.

Round 2
--Unit B wins initiative, so attacks first, rolling a successful hit as a 2nd level fighter vs AC 6. Damage is rolled as d6, resulting in 6. That 6 is multiplied by .833 (force multiplier) and 10 (# of fighters) to give 50 total damage.
-- Unit A then attacks, but rolls a miss, so no damage is taken by Unit B.
-- Total damage sustained by Unit A is now 67 (17+ 50), which is above their HP total, so their unit is broken automatically. They then roll on the broken unit table to determine results, which will determine what percentage of the unit is slain outright, and what percentage retreats in a rout.

Cohesion Check table

Unit Damage vs Individual Damage Explained

--At 50% and 75% unit damage, it is assumed that damage is being sustained across the unit, but no individual casualties have been sustained, as long as cohesion is maintained. However, if the cohesion fails, the unit is broken, and casualties could occur as the unit is routed (roll on Cohesion Failure Table).

--At 100% damage, unit cohesion is automatically broken, and casualties occur (roll on table to determine exactly how many). Surviving fighters all take some damage (as indicated on the table) and will attempt disorganized retreat.

--Commanding officers are always considered to be among the survivors of a broken unit. Their HPs are modified downward by the same percentage as the other surviving members of the unit.

--Under special circumstances, when a unit cannot or will not retreat (trapped, under mind control, undead, suicidal), they can continue fighting in a weakened condition. At 125% damage, the unit is wiped out totally.

Cohesion checks must also be made by individual units considering the state of the army as a whole, at 50% and 75%. Thus, if an army is made of 10 units, when 5 of those units are broken, the remaining five must immediate make cohesion checks. When 8 of the original 10 units are broken (passing the 75% mark), the remaining two units must make cohesion checks again. If the cohesion checks fail, no casualties are sustained, but the unit is broken and retreats.

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