Beginning chess players quickly learn the basic moves allowed by each piece and the fundamentals of capturing enemy pieces. But once the basics are learned, there are three special moves in chess that need to be learned and understood—two involving the pawn, and one unusual move that involves both the rook (castle) and the king.
The most common of the three special chess rules is called castling—a move that is normally used to improve the king's safety. Castling is the only move that allows two pieces, the king and a rook to move at the same time.
You can only castle if all of the following conditions are present:
If all of these conditions are met, you can castle:
This may sound confusing, but in practice it is simple. The black kings and rooks are positioned properly after castling.
Castling kingside is more common and leaves the king on the g-file while the rook moves to the f-file. Castling queenside leaves the king on the c-file, while the rook moves to the d-file. Files, in chess, are columns designated by a letter, as displayed in the diagram.
Pawns are the weakest pieces on the board, but they have the potential to become much stronger. Should a pawn manage to make it all the way to the other end of the board, that pawn must be promoted to any piece its player chooses, other than a king.
Generally, you would promote a pawn to a queen; however, you can also promote it to a rook, knight, or bishop. When the pawn is promoted to a queen, the move is often termed queening, and it is allowable for there to be two queens of the same color on the board. Sometimes a rook is used in an inverted position to designate the second queen.
Promoting to something other than a queen is known as underpromotion. Since the queen is the most powerful piece, promotion is for a queen. However, there may be a rare instance where the movement of a knight or other piece might offer an immediate benefit, in which case underpromotion is used.
En passant—a French term that means "in passing"—is probably the most confusing move for novice chess players. Players may not even know the move exists, making it the source of many arguments.
Before the 15th century, most people played by rules that didn't allow pawns to move two squares on their first move. When the two-square-pawn move was added to speed up the opening phase of the game, players noticed that the pawn could now sneak by an enemy pawn on an adjacent—something that was never possible when pawns plodded along at one square per move.
The solution was en passant, a move that allows a pawn that has moved two squares to be captured as though it had only moved one.
The following conditions must all be present for an en passant capture to be legal:
If all those conditions are met, an en passant capture is possible.