Balbo’s Chess
Balbo's Chess — starting position
https://engine.moddable.games/play/?game=chess&variant=balbos-chess
Balbo’s Chess was invented by M.G. Balbo in 1974 and is mentioned in Pritchard’s Encyclopedia of Chess Variants. It is played on an unusual diamond-shaped board with ten ranks of increasing then decreasing width, all centred on file f. All standard chess rules apply, but the board shape creates unusual opening dynamics and position-dependent promotion rules.
The Board
The board has 10 ranks, each centred on file f. The number of squares per rank (and the files present) is:
| Rank | Width | Files present |
|---|---|---|
| 1 | 3 | e, f, g |
| 2 | 5 | d, e, f, g, h |
| 3 | 7 | c, d, e, f, g, h, i |
| 4 | 9 | b, c, d, e, f, g, h, i, j |
| 5 | 11 | a, b, c, d, e, f, g, h, i, j, k |
| 6 | 11 | a, b, c, d, e, f, g, h, i, j, k |
| 7 | 9 | b, c, d, e, f, g, h, i, j |
| 8 | 7 | c, d, e, f, g, h, i |
| 9 | 5 | d, e, f, g, h |
| 10 | 3 | e, f, g |
Total: 3+5+7+9+11+11+9+7+5+3 = 70 squares. Files a–k (11 files at widest), ranks 1–10.
Starting Position
White:
- King e1 · Queen g1
- Bishop f1 · Bishop f2
- Rook d2 · Rook h2
- Knight e2 · Knight g2
- Pawns c3–i3 (7 pawns)
Black (mirror on ranks 8–10):
- King e10 · Queen g10
- Bishop f10 · Bishop f9
- Rook d9 · Rook h9
- Knight e9 · Knight g9
- Pawns c8–i8 (7 pawns)
Warning: Pritchard notes that both sides have an immediate N×f3/f8 mate in three moves available from the starting position. Players should be aware of this.
Promotion
Promotion rules depend on which square the Pawn reaches:
- Rank 10 (e10, f10, g10), d9, or h9 (the furthest reachable squares on files d and h, which disappear before rank 10): Pawn promotes to any piece — Queen, Rook, Bishop, or Knight.
- c8 or i8 (the furthest reachable squares on files c and i): Pawn may only promote to a minor piece (Knight or Bishop).
Note: Files c, d, h, and i do not reach rank 10 — they end at ranks 8 or 9 as the diamond narrows. Squares on those files at the edge of the board are the promotion squares for pawns on those files.
Rules
All standard chess rules apply (checkmate wins, stalemate is a draw, en passant, castling if reachable). The unusual board shape means there is no central pawn battle in the traditional sense — the two armies meet obliquely as the board narrows toward the centre of each side.
Attribution
Balbo’s Chess by M.G. Balbo, 1974. Documented at chessvariants.com/shape.dir/balbo.html (Hans Bodlaender and Fergus Duniho, from Pritchard’s Encyclopedia of Chess Variants).