How To Play Chess — special moves

Special Moves
There are two special moves that have not been talked about and have to be mentioned. They are en passant and castling.

En passant

En passant, which translates to "in passing" can be performed by white when white's pawn is on the fifth rank and the black pawn, which is on the seventh rank, moves to the fifth rank, trying to pass it without confrontation.

The pawns can only be separated by one column as well. So, for example, if the white pawn is on the fifth rank in column "A" and the black pawn is on the seventh rank in column "C", en passant can not be performed. Now if the black pawn was in the "b" column, en passant can happen. It's important to note that en passant doesn't happen if the opposing pawn moves from the sixth rank to the seventh. Only if the black pawn is on the seventh rank and attempts to move to the fifth, while the white pawn is one column over and on the fifth rank can en passant be performed. In this case, a picture is worth a thousand words and the illustration below shows en passant and the capturing process associated with it. Please note how the pawn captures in this instance because it's not typical of how pawns capture.

Note that if the player who can perform en passant doesn't do so on the very first try, they may not do so later.

Black can perform en passant as well, as you would guess. If a black pawn is on the fourth rank and, for example, in the "c" column and a white pawn is on the second rank and in column "b" or "d" (again, one column over from wherever the black pawn is) and attempts to move to the fourth rank (attempting to pass it and avoid confrontation), black may perform en passant. If white is on the third rank and moves to the fourth, black can't perform en passant. It has to occur when white, on his first move, moves from the second to the fourth rank.

Castling
Castling is a move done between the king and either one of the rooks. It is a special move that allows you to put the king in a very protective position. Since the object of the game is to put the opposing king in checkmate (which means your opponent ultimately will be coming after your king), this move is extremely important. There are two types of castling: castling king side and castling queen side. They're both illustrated in the picture below. Castling king side occurs when the king, which starts on the "e" square, moves to the "g" square. The rook takes the new position shown in the illustration. Castling queen side has the king start on the "e" square and move to the "c" square. Again, the rook takes the new position shown below. There are a few conditions that must be met before castling can occur, however.

Neither the king nor the rook involved in the castling may move before the castling occurs
The king can not castle when in check.
The king can not castle through a check

The first point is simple. For example, if you move the rook on the "h" square, you can not put it back, then perform castling king side. Once the rook on the "h" square has been moved, castling king side is no longer possible for the duration of the game. Similarly, moving the rook on the "a" square makes castling queen side impossible for the duration of the game. If you move the king before castling, castling is simply impossible, both king side and queen side, for the duration of the game.

The second point is also straightforward. If the king is in check, you may not castle to get out of check. You must block the opponen'ts attack or capture the attacking piece, then perform the castle on a subsequent move.

The final point needs a little more explaining and the illustrations below depict a player trying to casle through a check. For example, if a player is trying to castle king side and the opposing player's piece is attacking the "f" or the "g" square on the first rank, then castling is not permitted. Similarly, if a player is trying to castle queen side and the opposing player's piece is attacking the "d" or "c" square on the first rank, then castling is not permitted.