|Circe chess (or just circe) is a chess variant in which captured pieces are reborn on their starting positions as soon as they are captured, based on the following rules:|
- Pawns return to the start position on the same file they are captured on.
- Rooks, knights and bishops return to the starting square which is the same color as the square they are captured on.
For instance, a white pawn captured on b4 is reborn on b2; a black knight captured on f6 is reborn on b8; a black rook captured on the same square is reborn on h8. Castling with a reborn rook is permitted.
If the square that the rebirth should take place on is occupied, either by a friendly or enemy piece, the captured unit is not reborn--it is instead removed from the board and takes no further part in the game (like a capture in orthodox chess).
The rules of circe chess were first detailed by P. Monréal and J.-P. Boyer in an article in Problème, 1968.
These are the most usual rules employed in circe - there are numerous other forms of the game in which the rules of rebirth may vary.
When notating a circe game in algebraic notation, it is conventional to place details of where a captured piece has been reborn in brackets following the move. For example, if in the diagram to the right, white were to take black´s knight, this would be notated Rxe8(Ng8).
The position to the right demonstrates a couple of unusual effects which can occur in circe. It is black to move. White is threatening checkmate with 1.Re1#. Black would not be able to defend with 1...Kxe1 after this move, because the rook is instantly reborn on a1 from where it gives check (the fact that black´s bishop defends a1 is of no consequence - after Kxe1 it will be white´s move). It might appear that there is nothing black can do to prevent this threat, but in fact he has 1...Ba1! - if now 2.Re1+, Kxe1 is possible because the rook is not reborn owing to its rebirth square being occupied.
Circe is rarely played as a variant game (when it is, it is usually combined with progressive chess), but very often employed in composed chess problems.