Special Moves




Castling

Castling is a special move in the game of chess involving the king and either of the original rooks of the same color. Castling consists of moving the king two squares towards a rook, then moving the rook onto the square over which the king crossed.
Castling is considered a King move. Castling is permissible only if all of the following conditions hold:

  1. The King must never have moved.


  2. The chosen Rook must never have moved.


  3. There must be no pieces between the King and the chosen Rook.


  4. The King must not currently be in check.


  5. The King must not pass through a square that is under attack by enemy pieces.


  6. The King must not end up in check.


  7. The King and the chosen Rook must be on the same rank.


Pawn Promotion

If a Pawn advances all the way to its eigth rank, it is then promoted to a Queen, Rook, bishop, or Knight of the same color, the choice being at the discretion of its player. The choice is not limited to previously captured pieces.

Check

When a player makes a move that threatens the opposing King with capture (not necessarily by the piece that was moved), the king is said to be in check. If a player's king is in check then the player must make a move that eliminates the threat(s) of capture; a player may never leave his or her king in check at the end of his or her move.
The possible ways to remove the threat of capture are:
  1. Move the King to a square where it is not threatened.


  2. Capture the threatening piece (possibly with the King, if doing so does not put the King in check).


  3. Place a piece between the king and the opponent's threatening piece. This is impossible if the threatening piece is a Knight or Pawn, or if a checking Queen, Rook or Bishop is adjacent to the checked king. In the case of double check, when there are two pieces attacking the King, only a King move will get out of check; the King may capture an enemy piece.
In the case of double check, when there are two pieces attacking the King, only a King move will get out of check; the King may capture an enemy piece. A player may not make any move which places or leaves his or her King in check, even if the checking piece cannot move due to a pin, i.e. moving it would expose his or her own King to check. This also means that a player cannot place his King on any square adjacent to the enemy King, because doing so would leave his or her King able to be taken by the enemy King and therefore in check.


Checkmate

If a player's King is placed in check and there is no legal move that player can make to escape check, then the King is said to be checkmated, the game ends, and the checkmated player loses. Unlike other pieces, the king is never actually captured or removed from the board because checkmate ends the game.