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This page is written by both of the game's inventors, Michael Nelson and Peter Aronson.

# Separate Realms Chess

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## Introduction

In Separate Realms Chess, the standard 8 x 8 chessboard can be viewed as being broken into multiple sets of squares or "realms" depending on which pieces can get to them. Pawns, for example, are limited to a realm of six squares (seven counting the moment of promotion) unless they make a capture. The usual FIDE Bishops, being colorbound, are limited to realms of 32 squares. All of the pieces in Separate Realms Chess are limited to realms of 32 squares or less, except when they capture. Some pieces, such as Pawns and Bishops, are limited to realms of a lot less. All pieces can also change realms by capturing.

## General Rules

The rules of Separate Realms Chess are identical to those of FIDE Chess, except where noted below. The major difference in rules is that stalemate and three-times repetition are not draws, but loses for the stalemated or repeating player. The rest of the differences in rules have to do with the moves of the pieces.

## The Pieces and their Movements

All of the pieces in Separate Realms Chess have at least partly divergent moves; that is, at least some of the time they capture differently than move without capturing. This divergence between their capturing and non-capturing moves leads to them changing realm at least some of the time when they capture.

### The King

The King moves and captures by taking a single step diagonally, and can also capture (but not move without capturing) by taking a single step orthogonally. Its funny notation is FcW. This limits the King to the squares of one color -- a realm of 32 squares -- unless it captures. Opposing Kings start in different realms. Castling works as usual, and will cause the Rook to change realm when performed on the Queen-side.
 ``` +---+---+---+---+---+---+---+---+ | |:::| |:::| |:::| |:::| +---+---+---+---+---+---+---+---+ |:::| |:::| |:::| |:::| | +---+---+---+---+---+---+---+---+ | |:::| |:::| |:::| |:::| +---+---+---+---+---+---+---+---+ |:::| |:*:| ! |:*:| |:::| | +---+---+---+---+---+---+---+---+ | |:::| ! |:K:| ! |:::| |:::| +---+---+---+---+---+---+---+---+ |:::| |:*:| ! |:*:| |:::| | +---+---+---+---+---+---+---+---+ | |:::| |:::| |:::| |:::| +---+---+---+---+---+---+---+---+ |:::| |:::| |:::| |:::| | +---+---+---+---+---+---+---+---+```
The black circles/'*'s indicate where the King can both move and capture, the red circles/'!'s indicate where it can only capture.

### The Knights

Of the usual eight Knight's moves, the Separate Realms Chess Knight may make four of them -- the narrow forward and back ones -- with or without capturing. But the other four -- the wide forward or back moves -- may only be made when capturing. Its funny notation is fbNcsN. This limits the Knight to every other square on every other rank -- a realm of 16 squares -- unless it captures. The opposing Knights start in different realms.
 ``` +---+---+---+---+---+---+---+---+ | |:::| |:::| |:::| |:::| +---+---+---+---+---+---+---+---+ |:::| |:::| |:::| |:::| | +---+---+---+---+---+---+---+---+ | |:::| * |:::| * |:::| |:::| +---+---+---+---+---+---+---+---+ |:::| ! |:::| |:::| ! |:::| | +---+---+---+---+---+---+---+---+ | |:::| |:N:| |:::| |:::| +---+---+---+---+---+---+---+---+ |:::| ! |:::| |:::| ! |:::| | +---+---+---+---+---+---+---+---+ | |:::| * |:::| * |:::| |:::| +---+---+---+---+---+---+---+---+ |:::| |:::| |:::| |:::| | +---+---+---+---+---+---+---+---+```
The black circles/'*'s indicate where the Knight can both move and capture, the red circles/'!'s indicate where it can only capture.

### The Bishops

Bishops in Seperate Realms Chess while capturing and moving without capturing differently, capture and move without capturing in the same directions. The Bishop moves without capturing like an Alfil-Rider, making repeated two square diagonal jumps until reaching the edge of the board, an occupied square, or the player decides to stop. The Bishop captures like a FIDE Bishop, sliding diagonally. The piece's funny notation is mAAcB. This move limits the Bishop to 1/8 of the board -- a realm of 8 squares -- unless it captures. All four Bishops start in different realms.
 ``` +---+---+---+---+---+---+---+---+ | ! |:::| |:::| |:::| |:::| +---+---+---+---+---+---+---+---+ |:::| ! |:B:| |:::| |:::| ! | +---+---+---+---+---+---+---+---+ | |:::| ! |:::| |:::| ! |:::| +---+---+---+---+---+---+---+---+ |:+:| |:::| ! |:+:| ! |:::| | +---+---+---+---+---+---+---+---+ | |:::| |:::| B |:::| |:::| +---+---+---+---+---+---+---+---+ |:::| |:::| ! |:::| ! |:+:| | +---+---+---+---+---+---+---+---+ | |:::| ! |:::| |:::| ! |:::| +---+---+---+---+---+---+---+---+ |:::| ! |:::| |:::| |:::| ! | +---+---+---+---+---+---+---+---+```
The uppermost Bishop is demonstrating the non-capturing moves, the lowermost the capturing moves. The green circles/'+'s indicate where the Bishop can move without capturing, the red circles/'!'s indicate where it can only capture.

### The Rooks

Like the Bishops, the Rooks in Seperate Realms Chess while capturing and moving without capturing differently, capture and move without capturing in the same directions. The Rook moves without capturing like an Dabbabah-Rider, making repeated two square orthogonal jumps until reaching the edge of the board, an occupied square, or the player decides to stop. The Rook captures like a FIDE Rook, sliding orthogonally. The piece's funny notation is mDDcR. This move limits the Rook to 1/4 of the board -- a realm of 16 squares -- unless it captures. All four Rooks start in different realms.
 ``` +---+---+---+---+---+---+---+---+ | |:::| |:!:| |:::| |:::| +---+---+---+---+---+---+---+---+ |:+:| |:R:| ! |:+:| |:+:| | +---+---+---+---+---+---+---+---+ | |:::| |:!:| |:::| |:::| +---+---+---+---+---+---+---+---+ |:::| |:+:| ! |:::| |:::| | +---+---+---+---+---+---+---+---+ | ! |:!:| ! |:R:| ! |:!:| ! |:!:| +---+---+---+---+---+---+---+---+ |:::| |:+:| ! |:::| |:::| | +---+---+---+---+---+---+---+---+ | |:::| |:!:| |:::| |:::| +---+---+---+---+---+---+---+---+ |:::| |:+:| ! |:::| |:::| | +---+---+---+---+---+---+---+---+```
The uppermost Rook is demonstrating the non-capturing moves, the lowermost the capturing moves. The green circles/'+'s indicate where the Rook can move without capturing, the red circles/'!'s indicate where it can only capture.

### The Queen

The Separate Realms Chess Queen moves like a combination of the Separate Realms Chess Bishop and the Separate Realms Chess Rook. Its funny notation is mAADDcQ. This move limits the Queen to 1/4 of the board -- a realm of 16 squares -- unless it captures. The Queens start in different realms.

### The Pawns

Separate Realms Chess Pawns move just like regular FIDE Pawns. After all, they already are divergent and confined to a realm of consisting of a file minus the first and last squares.

## Variant

The Pawns can be moved forward to the 3rd rank (no double-move and no en-passant). This slows the game down and creates dynamic tension in pawn play (allow development vs. create weakness).

## Notes

This game was created in the Chess Variant Pages' comment system. Peter Aronson posted an idea for a piece (the Separate Realms Chess Rook), and Mike Nelson created equivalent pieces for the rest of the array except the Pawns (which are already limited to a realm and divergent, anyway) and the King, and created a game from it. Peter then built a ZRF and worried out loud about drawishness, so Mike made the King colorbound and divergent like everything else. Peter continued to worry and suggested win by stalemate, and here the game is! Jörg Knappen and Jared B. McComb added some useful comments too.

A game that takes the theme of colorboundness even further and which served as a partial inspiration for this game is Ralph Betza's Colorboundmost Chess.

Some other variants built around divirgent pieces are Frank Maus's game of Thinktank Chess, A.J. Winkelspecht's game Divergent Chess, Michael Howe's game Biform Chess and Christian Freeling's game Loonybird.

An alternate way of looking at realms. We can think of the board as having four realms:

1. White squares on odd ranks.
2. Black squares on odd ranks.
3. White squares on even ranks.
4. Black squares on even ranks.
Considering only non-capturing moves, the Queen, Rooks, and Bishops are confined to their starting realms (in the case of the Bishops, to half of it.) The Knight alternates between two realms with opposite colors and the same parity (odd/even). The King alternates between two realms with the same color and opposite parity. The Pawn (disregarding the double step) alternates between two realms of opposite color and parity. This is an interesting symmetry: the long range pieces are confined to a single realm, the short range pieces alternate--with each short-range piece type having one of the three possible alternation patterns.

With every piece able to jump the pawn line, development is fast and furious (and more than a little dangerous). Pawn play is nothing like FIDE chess, as a pawn can help development by standing still!

## Computer Play

An implementation of Separate Realms Chess has been written for Zillions of Games. You can download it here:

Written by Peter Aronson and Michael Nelson.
WWW page created: August 3rd, 2002.
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