Muster Chess

Muster Chess is a variant that allows players to construct their own armies and to penalise opponents whose armies are much stronger than the regular army from Orthodox Chess.

Each game begins with a phase called a Muster, after which the rules are the same as Orthodox Chess, although the rules for castling and pawn movement are adapted for different armies.

Setup

Before the game, each player must construct an army that fits on the first four ranks of the board: it may have any number of Queens, Rooks, Bishops, Knights, or pawns, but must have exactly one King. One player should construct a White army (with the King on their right side of the board) and the other a Black army (with the King on their left side of the board). There are no further restrictions on the army’s strength or formation: an army with a King and 31 Queens is permissible.

The Muster begins with the players revealing the armies they have mustered (brought to the game). Players have a set period of time to assess the two armies and choose which they would prefer to use, and then both choices are simultaneously revealed. If both players have chosen the same army, it is assigned to the player who did not muster that army, and their opponent is assigned the regular army of the opposite colour. If the players choose different armies, they are assigned the army of their choice.

Rules

After the Muster, play commences as per Orthodox Chess, with the White army moving first. The modifications to the rules for castling and pawn movement are described below.

Castling may occur under the following conditions: the player’s King and Rook started the game on the same rank or file, neither have moved, and they are separated by nothing but empty squares. To castle, the King moves towards the Rook, which moves to the square adjacent to but on the other side of the King. The King moves one, two, or three squares, depending on how far he is from the Rook. If he is adjacent to the Rook, he moves one square; if he is two, three, or four squares from the Rook, he moves two squares; if he is more than four squares from the Rook, he moves three squares†. The King cannot castle while in check, nor can he pass through or into check.

Pawns may move forward any number of empty squares if they remain on the player’s half of the board, even if they have already been moved. Pawns on the first rank may move forward up to three squares; pawns on the second rank may move forward up to two squares; pawns on other ranks may only move forward one square. Pawns that move forward more than one square in a turn are vulnerable to capture en passant at each intermediate square by enemy pawns on the opponent’s next turn.

Notes

Effects on Gameplay

Muster Chess substantially changes chess openings and game preparation. Players will not know which army their opponent will muster, so opening preparation consists of:

• carefully constructing or choosing an army to muster

• preparing against a variety of armies, or against one your opponent is likely to muster

• preparing to play against the army you muster using the regular chess army

Players tend to muster armies that are equivalent in strength to the regular chess army, although better prepared players are able to muster slightly stronger armies. To understand why, let us consider three scenarios in which Player A musters an army with the same strength as the regular army as she faces three opponents: Players X, Y, and Z.

Player X musters an army that is weaker than the regular army. Both players are likely to choose Player A’s army, as it is the stronger of the two, so Player X is assigned the army Player A mustered, and Player A is assigned the regular army. These armies have equal strength, but Player A has the advantage, as she has been able to prepare for this situation, whereas Player X has not.

Player Y musters an army that is considerably stronger than the regular army, which is likely to be chosen by both players. So Player A is assigned the considerably stronger army, and Player Y is assigned the regular army. While Player Y has been able to prepare for this situation, he is still disadvantaged by facing an army which is considerably stronger.

Player Z musters an army that is slightly stronger than the regular army, and he has thoroughly prepared for playing the regular army against the army he is mustering. When the Muster begins, Player Z chooses the army he mustered, as it is slightly stronger than the alternative. Player A’s decision is more difficult: if she chooses the army she mustered she faces an army that is slightly stronger than her own, but if she chooses the army mustered by Player Z she will have only a slightly stronger army but she will be unprepared against an opponent who is thoroughly prepared for this situation. Whichever choice Player A makes, she is at a disadvantage.

Therefore, players who are ill-prepared should muster an army that is equivalent in strength to the regular army, but well-prepared players should muster an army that is slightly stronger. If two well-prepared players face each other with armies that are slightly stronger than the regular army, both will need to consider choosing the army mustered by their opponent, risking a situation in which they have a slight advantage in army strength but for which they are completely out-prepared.

Rationale

Many games of Orthodox Chess are won by whoever has memorised more openings. As a result, games often follow familiar paths for the first dozen turns or more, and in order to be competitive, players must prepare for games by memorising trees of openings, an activity that few enjoy. Muster Chess, however, has trillions of possible armies, resulting in unique games for which memorisation is not the primary form of preparation.

The goal of removing the drudgery of memorisation has driven the creation of various forms of Baseline Chess, in which the back rank of the chessboard is randomised in some way. In Fisher Random Chess, each game begins with one of 960 configurations being randomly selected. This removes the need to memorise openings, but it also deprives players of any sense of ownership: they must spend the first minutes of each game trying to understand the configuration of their own army. In Muster Chess, on the other hand, players will know the strengths and weaknesses of the army they bring to the table: they just won’t be able to prepare for how it interacts with the enemy. In Pre-chess, the pawns start as they do in Orthodox Chess, but players take turns placing the regular chess pieces on the back rank of the board. While this allows for players to choose their own armies, it suffers from the same problem as Orthodox Chess: good players must memorise the pre-game sequence of piece placement in order to be competitive. While Muster Chess players must learn how to choose an effective army, evaluate an opponent’s army, and be prepared to play against their own army using the regular army, players no longer have an arms race in which they must out-memorise their opponents.

Muster Chess can be combined with High Chess to make Freestyle Chess or Royal Chess. In the latter, players may muster and promote to Princes (R+N) and Princesses (B+N).

Muster Chess was originally published here on Reddit.

† When castling, the King moves the ceiling of the square-root of his distance from the Rook. If Muster Chess were being played on a larger board and the King and Rook were separated by 10 squares, the King would move four squares to castle.

Last revised by Grant Sinclair.