Diceless 8x8 Chessgammon

Bear With Me

In order to understand this game, you need to know a few words from the language of Backgammon.

The object of the game is to move all of your pieces off the end of the board. Moving off the end is called "bearing off".

When a piece is captured, it is placed "on the bar", and must be brought back into the game. In backgammon, if you have a piece on the bar, but can't bring it in, you cannot move.

Backgammon is different from chess. In Backgammon, you can have more than one piece at the same board location, and a stack cannot be captured. A single piece is called a "blot" and can be "hit" (captured). Most of all, backgammon uses dice.

The Rules of Diceless Backgammon

The standard rules of Chess apply in the few cases not covered by the following rules.
There is no check. There is nothing special about the King.
The object of the game is to move all of your pieces off the end of the board. For the purposes of notation, "bearing off" is written as a move to the 9th rank, even if you are playing Black.
Note: a Bishop on h1 cannot be borne off in one turn because there is no imaginary square to the left of a9.
When a piece is captured, it is placed "on the bar". A piece on the bar needs to be brought back into the game. For the purposes of notation, "bringing in" is written as a move from the 0th (zeroth) rank, even if you are playing Black.
If you have a piece on the bar, you might not be able to move. If you have a piece on the bar, there are only three ways you can move:
1. You can bring the piece back from the bar onto an appropriate square,
2. You can make a capture,
3. Only if you can do neither of the other two things can you make a move that vacates an "appropriate square" that you need for bringing-in.
Further on, there's a paragraph called "design notes", which might help clarify this rule.
Appropriate Square: When you bring a piece back from the bar, it must be placed on a square which is currently empty, and on which a piece of the same color and type started the game.
For example, a White Rook can be brought back only to a1 or h1, a White Pawn can be brought back to any square on the second rank, and a White King can only be brought back to e1.
There is no such thing as stalemate. If you cannot move, the other player goes again. If neither player can move, the game is a draw by repetition!
If both players bear off their last piece on the same move number, the game is a draw.
Pawns on the 8th rank are not promoted. A Pawn on the second rank can always make a two-step move.
Castling would be silly. It's not permitted.
The author would prefer that you play this game with different armies.

Design Notes

One critical thing about Backgammon is that you can sometimes hit a few blots and then bear off all your pieces while the opponent is unable to move.

In Backgammon, you protect your pieces from being hit by piling many pieces up on one board location, but an unlucky roll of the dice may force you to break up your formation and leave a blot. This probably wouldn't work in Chess, because there are no dice. If you want to try it, I'd suggest Diceless 4x8 Chessgammon, with two pieces per square in the initial setup:

 rnbqkbnr
 pppppppp
 . . . .
 . . . .
 . . . .
 . . . .
 PPPPPPPP
 RNBQKBNR

In Chess, you protect your pieces by mutual destruction: if one of your pieces is captured, you recapture. Therefore in Diceless Chessgammon you are permitted to make any capturing move you wish, even when you have pieces on the bar. If you allow multiple pieces per square, discard this rule.

In Backgammon, you can have many pieces on the same board location, so your own pieces do not prevent you from bringing captured pieces back in from the bar. Therefore in Diceless Chessgammon you are permitted to move any piece that occupies a square you need for bringing-in, even when you have pieces on the bar. If you allow multiple pieces per square, discard this rule.

In Backgammon, all the pieces move the same way, but the distance is determined by dice; and you get two moves per turn. The different moves of the chess pieces correspond to the different rolls of the dice, and you could consider playing Doublemove Diceless Chessgammon. If you allow multiple pieces per square, playing Doublemove is probably a bad idea.

Strategy

It would be foolish to bear off all your long-range pieces and leave your Pawns and King on the board.

It seems like this game could go on for a long time. You advance a Pawn, trying to bear it off, it gets captured, you have to start all over. In fact, what I think must happen in this game is that you play for paralysis above all else: for example,

 r n b q k b n r
 p p p p p p p p
 . . . . . . . .
 . . . . . . . .
 . . . . . . . Q
 . . . . . . . R
 P P P P P P P P
 . N B . K B N R

1. Qh4:h7 Rh8:h7 2. Rh3:h7 Rh0-h8 3. Rh7:h8 h0-h7 4. Qd0-d1 5. h2-h4 6. Rh1-h3 7. Rh3-a3 8. e2-e3 9. Qd1-g4 10. Qg4-a4

Even with Black unable to move, progress is slow. Capturing on h7 would allow Black to move a Pawn off the second rank; capturing anything else allows a recapture. It is very possible for you to stalemate the opponent and lose anyway.

Partial immobility of the opponent is achieved by "winning a piece" in the traditional way, and thereby putting more enemy pieces on the bar than friendly ones. When the captures are finished, you get at least one free move with which to advance your development. For example, 1. e4 e5 2. Nf3 Nc6 3. Bb5 a6?! 4. B:c6 d:c6 5. N:e5 Nb0-b8 6. Bf0-f1 e0-e7 7. Ne5:f7!? Ke8:f7 8. Ng0-g1 d0-d7 9. Ng1-f3; Black was forced to block his own development with Pawns at e7 and d7, White must have some degree of advantage, and this advantage grew from the diminished choice caused by "winning" the Pawn at e5, at which point Black had two pieces to bring in but White had only one.

Evidently, the strategy of this game must be to develop your pieces and try to immobilize the opponent, either completely or partially. The game might take a large number of moves (making it unsuitable for postal or email play), but the same is true of all games that allow pieces to be reincarnated -- at least this game *can* be finished, unlike Mangiasputa!

Variants

The spirit of V. R. Parton whispered a suggestion in my ear, so here is

Racing Kings Chessgammon

The rules of Diceless Chessgammon and Racing Kings are mixed together.

The King may not be checked, nor may he move into check.

Chessgammon capture and rules of bringing-in are used.

You win by bearing off all your pieces.

Racing Kings Chessgammon is bound to be a shorter game than the other variation, and the strategy of when to bear off the King looks interesting.

Hans Bodlaender's Chessgammon

Pieces that are captured are counted as borne off.

I haven't studied this closely, but it's an interesting idea because capturing pieces is very undesirable. However, it isn't really Chessgammon because there are no pieces on the bar to be brought back in.

I think this should be seen as a form of Giveaway Chess, but without forced capture. As long as there's a way to force your own pieces off the board, forced capture is not needed.