Tuesday, February 5, 2013

Mass Combat Rules, Take 1

I've been working on some mass combat rules over the last six months or so, with the general aim of having them as a resource in case I get the chance to run a Birthright style game sometime down the road. They might be of interest to other GMs.

Note "drawing for initiative" refers to my earlier posts about savaged initiative. The "Vis", "Unit Maintenance", and "Mustering Costs" refer to my as-yet-unfinished domain management rules.


The Rules

These rules assume that the PCs are commanders with authority over a large number of troops. 

Combat Units:  Combat units are defined by a battle die (ranging from 1d4 to 1d12), an Encounter Power, a movement speed (in 100' increments), and a pool of Morale Points (ranging from 1 to 3) to represent durability.   (Units also have muster and maintenance costs, but these do not affect mass combat.)  Units do not have their own initiative; instead, they act on the initiative of the PC or NPC who commands them. 

Initiative: Commander initiative is determined by base THAC0.  Commanders with THAC0s of 15 or greater draw two cards and take the worst; commanders with THAC0s between 14 and 10 draw a single card; and commanders with THAC0s of 9 or less draw two cards and take the best.  Certain backgrounds and items may improve this draw by up to one step.

The mass combat is played out on a hex grid.  Each hex is about 100' across.  Generally, terrain is divided into clear terrain (units may move full speed); moderate terrain (units move at half speed); difficult terrain (all units move one square per round); and impassible terrain.  Unit markers are longer than they are wide to represent column facing.

Mass combat occurs in one-minute combat rounds.  As with small-scale combat, commanders declare their actions before drawing initiative.   On their initiative counts, commanders may (1) issue movement orders, (2) order a unit to use an "on command" encounter power, (3) rally their troops , (4) cast spells, or (5) take some other player-defined action.  Commanders who draw the joker may take two actions in a mass combat round, but this does not confer upon any troops the ability to act twice.

  1. Command Units to Move:  The commander may issue a single command to any number of unengaged units on the field.  Only unengaged units may be designated (see below for engagement rules).  Every designated unit receives the same command, which it follows to the best of its ability.  Example  commands include "advance at your maximum speed", "wheel 90 degrees to the left", and "advance 100 feet".  If, during its movement, a unit becomes adjacent to an enemy unit, it immediately stops moving and becomes engaged (see below for engagement rules). Once a unit has been commanded, it cannot take any further actions in this combat round.

  1. Command troops to use an "On Command" encounter power:   Some Encounter Powers have the trigger “on command”.  A commander may order any number of units to use a single Encounter Power.  The commander may choose only one Encounter Power that is to be used.  Any number of units having an Encounter Power by that name may then use the power.  If the Encounter Power allows a choice in targets, the commander is free to designate each unit’s target. Once a unit has been commanded, it cannot take any further actions in this combat round.

  1. Rally Troops:  On their initiative count, commanders may attempt to rally their troops, causing them to regain the use of an expended Encounter Power.  Engaged units and units that have already been commanded this round may still be rallied.  To rally their troops, the commander simply makes a charisma check.  If the check is successful, make note of the amount by which the check was passed--this is the number of Morale Points worth of units that the commander may rally this round.  Rallying a unit does not take up its action for this round--it still may be commanded.

  1. Cast Spells:  The results of spell casting will be adjudicated on the fly, taking into account the effect the spell would have on a representative member of the target unit.   As a rule of thumb, the total area affected by a spell must be equal to at least 1/2 the size of the target unit  in order to have any appreciable effect on the mass combat.  Typical outcomes may be the loss or gain of morale points; restricted, impeded or enhanced movement; a bonus or penalty to the unit's battle die rolls; or the creation of new units on the field of battle. In addition, powerful spell casters may gain access to battle spells.  Battle spells cost vis and require access to a Battle Magic Supply Train.

  1. Player-Defined Action: Nothing prevents players from taking other actions not listed above.  Note that any commander in proximity to his own troops benefits both from concealment and good cover, as if he was hiding behind an arrow slit.

Engaged Units: If a unit enters a square adjacent to an enemy unit, both units stop moving and become engaged in combat.  Engaged units may not move until the enemy unit has been destroyed.  Apart from certain encounter powers, there is no option to disengage once a unit has been committed to combat.

Ending the Round: After the last commander has acted, engaged units roll their battle die to determine the result of their combat this round.  A unit deemed to have a minor disadvantage (such as fighting from lower ground) takes a -2 penalty to its roll.  A unit flanking another unit rolls two battle dice and takes the higher roll.

Compare the rolls of each opposed unit.  If any unit's roll exceeds that of its foe by 3 or more, the winning unit inflicts one point  of morale damage, plus one additional point for every additional +2 by which the winning roll exceeds the losing roll.  If a unit's morale point total drops to zero, it is routed from the field and removed from the mass combat.

Once all engaged units have rolled their battle dice, the combat round is complete, and play continues with commanders declaring actions and drawing initiative for a new combat round.

Sample Encounter Powers

Launch Volley: On command, inflict 1 morale damage on an unengaged unit within 10 squares.

Feast on the Weak: On engaged with a unit that has 2 or less morale, the opposing unit is destroyed.
Spirited Charge: On engaged, the opposing unit suffers 2 morale damage.
Receive Charge: On engaged with a unit of large creatures, the opposing unit suffers 3 morale damage.
Sow Confusion: On engaged, the opposing unit’s encounter power is expended with no effect.
Shatter Arms: On engaged, the opposing unit’s battle die is reduced by one step for the remainder of the encounter.
Raise Shield Wall: On command, all damage suffered this round is reduced by 1.
Cast Pilum: On engaged, the opposing unit’s speed is reduced by 2 for the remainder of the encounter.  Optionally, may also become disengaged and move backward 2 squares.
Gout of Flame: On command, all units within a forward-facing line 5 squares long take 4 damage.

What's influencing me right nowBirthrightA Song of Fire and IceXCOMArs Magica

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