Fork (chess)

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The white knight forks the black king and rook. (It is particularly effective to fork a king and another piece: the rules require immediate attention to a check to the king.) Black cannot choose to defend another piece, nor can he make an intermediate move (zwischenzug) to complicate the situation; the king must move, after which White can capture the rook. In return, Black's pawn on g4 forks the white rooks. But White can escape loss of material, since after Black's king moves out of check, one of the rooks can deliver check again, allowing the other rook to escape next move.

In chess, a fork is a tactic that uses a single piece to attack multiple pieces at the same time. The attacker usually hopes to gain material by capturing one of the opponent's pieces. The defender often finds himself in a difficult position in which he cannot counter all threats. The attacking piece is known as the forking piece. Conversely, the pieces that the forking piece is attacking are said to be forked.

A piece that is defended can still be forked. In this situation, material gain is still possible, if the forking piece has lower value.

Forking piece

The type of fork is commonly named after the type of forking piece. For example, in a knight fork, a knight moves to attack two or more opponent's pieces in the same move. Any type of piece may perform a fork, including a king, and any type of piece can be forked. A fork is most effective, when it is forced or when the king is under attack.

Knights are often used for forks; they jump to a position where they simultaneously attack two pieces and cannot be counterattacked.

A queen move also often attacks two pieces at the same time, but this typically gains material only if both pieces are undefended, or if one is undefended and the other is the opposing king. Since the queen is usually more valuable than the pieces it is attacking, it usually only gains material forking undefended pieces. The possibility of a queen fork is a very real threat when the queen is out in the open, as is often the case in an endgame. A fork by a protected queen of the opposing queen and king (or an undefended piece) can be useful if the forking player wants to force an exchange of queens.

Pawns can also fork enemy pieces. By moving a pawn forward, it may attack two pieces: one diagonally to the left and the other diagonally to the right. In the diagram to the upper-right, the black pawn is forking the two white rooks.

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The white queen is forking the black king, rook and bishop. The white pawn is forking the black knights. The black queen is forking the white rook, bishop and knight. The black pawn is forking two of White's minor pieces.

Forked pieces

The term royal fork is sometimes used to describe the situation where the king and queen are forked  – thus being the highest material-gaining fork possible. Another term, the grand fork, is sometimes used to describe the situation where the king, queen, and one (or both) rooks are forked.

Tissir–Dreev 2004

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Position after White's 33rd move

The example to the right is from the first round of the FIDE World Chess Championship 2004 between Mohamed Tissir and Alexey Dreev. After 33... Nf2+ 34. Kg1 Nd3, White resigned. In the final position the black knight forks the white queen and rook, so that after the queen moves away, White will lose the exchange.

Forks are often used as part of a combination which may involve other types of chess tactics as well.

Forks can be escaped when the king is not under attack. A forked piece such as the queen could check the enemy king. Afterwards the second forked piece could be moved to safety.

See also

• Skewer

References

• Golombek, Harry (1977), Golombek's Encyclopedia of Chess, Crown Publishing, ISBN 0-517-53146-1 

• Hooper, David; Whyld, Kenneth (1992), The Oxford Companion to Chess (2nd ed.), Oxford University Press, ISBN 0-19-866164-9 

External links

• Chess Tactics Repository - Forks - Collection of chess problems involving forks