mass combat: chess-based, Mosaic Strict-complaint

Use cases

These are most relevant for big battles in cod-medieval fantasy settings that your guy is commanding as a general, and which you might plausibly win or lose. Skirmish-level fights, the logistics of military campaigns, surviving or winning renown as a warrior in the midst of mass-battle-as-dangerous-environment, and the like are better served by different rules or none at all.

Physical materials

You'll need

1. A pair of timers, such as exist on your phone, or a chess clock if you want to get fancy.
2. A chess set, or a customizable online version of chess such as protochess.

Army construction

If your army contains...

1. ...seige equipment or fortifications, get a rook. If they occupy a permanent fortification or have the high ground, get another rook.
2. ...a renowned warrior or super tough guy like a giant or something, get a knight. If they contain a whole company of such, get a second knight.
3. ..a powerful wizard or creature with neato abilities like a basilisk or something, get a bishop. If they contain a whole cabal of the bastards, get a second bishop.
4. ...a really powerful wizard, or a dragon or archangel or something, get a queen. 
5. ...a PC who isn't one of the above, get a king for each. (If PCs do fall into these categories, designate the relevant pieces as PCs.)
6. ...x random weaklings, get ln x pawns.

Army placement

Place the GM's screen over the middle of the chess board, then each army is placed however their commander likes... unless they've been caught with their pants down, in which case their pieces are placed randomly (but still secretly.) Pieces representing PCs can be placed deliberately (if the battle commences by enemies hacking at the PCs in their tents you probably want to use a different system). If you're placing randomly on a physical board I suggest literally dumping all the pieces on it and standing them up as close to where they fall as you can manage as a sort of premonition of the disaster that's about to be-fall them.

The "pants down" clause can apply to both parties, as with two armies randomly bump into each other en route and start confusedly fighting.

Timer

Each side operates on a ten minute timer by default. Double that if the fictional general you're playing is decent at being a general, and triple it if they're a brilliant general (half it if they're actively incompetent.) If you, the player, suck at chess, double it, but if you're pretty good, halve it, and if you're actively great, halve it again. (All the same applies to the GM and the NPC general they're playing.)

If the timer runs out, the other side gets three free moves and then you start again.

The battle itself

Play chess like normal, with the following changes:

1. The pawn promotion rule does not apply.
2. Neither do lame made up rules like en passant or castling.
3. Kings can enter check.

There are no victory conditions. Instead, battle ends when one side has had enough and decides to flee, surrender, or otherwise not engage in the kind of mass combat represented by this minigame.

After the battle

Pieces captured in game represent casualties, but casualties need not represent death. Flight, wounds of various levels, shell-shock, and literally being captured are all possibilities. If GM doesn't have any diegetic intuitions for some particular case - which may not be clear until well after battle in the confusion of regrouping - roll a d6:

1. killed
2. mortally wounded
3. wounded, will be fine with proper care, but won't be able to keep up with a march
4. fled
   
5. captured
6. shellshocked
   

Attestation (and the relevant rules of chess)

These are rules compliant with Mosaic Strict, meaning they're compliant with everything. 

 

Unless referring externally to the rules of chess compromises the independence of these rules? Okay, here's how chess works: the game is played on an 8x8 board of squares, each occupied by pieces owned by a player. Players take turns moving pieces from one square to another per the following rules:

• Pawns move one or two squares on their first turn if moving into a square not occupied by another piece, or diagonally one square if moving into a square occupied by an enemy piece. They can only move away from the side of the board on which they were placed
  
• Rooks move any number of squares horizontally and vertically.
  
• Knights move two squares in one direction and then one square in a direction orthogonal to that.
• Bishops move any number of squares diagonally.
• Queens move any number of squares horizontally, vertically, or diagonally.
• Kings move one square horizontally, vertically, or diagonally.

You can't move into a square occupied by one of your own pieces. If you move into a square occupied by another player's piece, that piece is "captured" and removed from play.