Seirawan chess

Seirawan chess uses the standard 8 by 8 board and begins from the normal position. Each side also receives two pieces that wait off the board: a hawk and an elephant. Yasser Seirawan and Bruce Harper created the variant in 2007.

The two new pieces

• The hawk combines the moves of a bishop and knight. It may slide any distance diagonally without crossing pieces, or jump in the knight's L-shaped pattern.
• The elephant combines the moves of a rook and knight. It may slide any distance along a rank or file without crossing pieces, or jump like a knight.

They are compound pieces because each combines the powers of two familiar pieces. Their movement matches the archbishop and chancellor in Capablanca chess, although Seirawan chess gives them different names and a different method of entering play.

Entering from reserve

The defining mechanism is called gating, meaning that a reserve piece enters through a newly vacated square. When a piece that began on the back rank, the row where the king and other non-pawn pieces start, moves from its original square for the first time, the player may place an available hawk or elephant on the square just vacated. The placement is part of the same move.

This is not a free drop onto any square. The opportunity exists only when an original back-rank piece first leaves its starting square. If those pieces move or are captured without admitting the reserves, the corresponding gates disappear. A hawk or elephant that never enters may remain out of play for the entire game.

During castling, the special joint move of a king and rook, the player may gate one reserve piece onto the king's original square or the participating rook's original square, but not both. A pawn reaching the last rank may also promote, meaning be replaced by a stronger piece, to a hawk or elephant in addition to the usual choices.

What it adds to play

Developing a piece, meaning moving it away from its starting square so it can participate, may simultaneously introduce a powerful new unit. Move order therefore manages gating opportunities as well as ordinary development. Keeping a reserve preserves flexibility, but waiting too long can close every available gate.

The familiar opening position makes the game approachable, but the compound pieces quickly alter attacking geometry. A rook, bishop, or queen leaving the back rank can open a line and receive immediate support from the newly gated piece.