Circe chess
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. The game was invented by French composer Pierre Monréal in 1967 and the rules of Circe chess were first detailed by Monréal and Jean-Pierre Boyer in an article in "Problème", 1968. Circe is rarely played as a variant game (when it is, it is usually combined with progressive chess), but very often employed in composed fairy chess problems. Rules. 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. 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. A reborn pawn regains its initial two-step move option. A captured promoted piece is treated as a piece (not a pawn). 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). If a pawn captures via "en passant", it would be immediately in front of the reborn opponent's pawn, thus preventing either pawn from moving. Philip Cohen has suggested that a move that simply reverses the opponent's previous move should not be permitted. (For example, White Qd1, Black Bg4: if White plays Qxg4, the bishop is reborn on c8, and Black should not be permitted to immediately recapture Bxg4.) Example. The position illustrated 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 (Black's bishop does defend a1, and the black king is free to move to e2 or capture at d2, but this is of no consequence as 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 because its rebirth square is occupied. Notation. When notating a Circe game in algebraic notation, it is conventional to place details of where a captured piece has been reborn in parentheses following the move. For example, if in the example diagram, White were to take Black's knight, this would be notated Rxe8(Ng8). Circe variants. There are many variants of Circe, especially in chess problems. Instead of being reborn on their starting positions the pieces may be reborn on other locations. References. Bibliography