Fork (chess)

In chess, a fork is a tactic whereby a single piece makes two or more direct attacks simultaneously. Most commonly two pieces are threatened, which is also sometimes called a double attack. The attacker usually aims to gain material by capturing one of the opponent's pieces. The defender often finds it difficult to counter two or more threats in a single move. The attacking piece is called the forking piece; the pieces attacked are said to be forked. A piece that is defended can still be said to be forked if the forking piece has a lower value.

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The white knight forks Black's king and rook. Black's pawn forks the white rooks.

Besides attacking pieces, a target of a fork can be a direct mating threat (for example, attacking an unprotected knight while simultaneously setting up a battery of queen and bishop to threaten mate). Or a target can be an implied threat (for example, a knight may attack an unprotected piece while simultaneously threatening to fork queen and rook).

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

Forking piece

The type of fork is named after the type of forking piece. For example, a knight fork is a knight move that attacks two or more enemy pieces simultaneously. Any type of piece can perform a fork—including the king—and any type of piece can be forked. A fork is most effective when it is forcing, such as when the king is put in check.

The knight is the quintessential forking piece; in fact, some sources only use the term "fork" when a knight is the attacker, while if another piece is the attacker the tactic is called a double attack or similar. A knight fork is powerful in several ways. The piece's unique L-shaped move allows it to attack any other type of piece without being threatened back by its targets, in seven different directions (eight minus the space it moved from). Another advantage of the knight in forking is the ability to jump over any piece freely.

The queen is also often used to fork, but since the queen is usually more valuable than the pieces it attacks, this typically gains material only when the pieces attacked are undefended or if one of them is the king and the other is undefended. The possibility of a queen fork is a very real threat when the queen is in the open, as is often the case in endgames. If a player wants to force an exchange of queens, forking the enemy queen and king (or an undefended piece) with a protected queen can be useful.

Pawns other than rook pawns (those on the a- and h-files) can also be used to fork by attacking two enemy pieces diagonally—one to the left, the other to the right.

Forks made by the king are an important consideration in endgame, where the king's ability to attack multiple pieces at once affects where (for example) a pawn's defenders can be safely placed.

Other terms

If the King is one of the attacked pieces, the term absolute fork is sometimes used. A fork not involving the enemy king is in contrast a relative fork.[1]

A fork of the king and queen, the highest material-gaining fork possible, is sometimes called a royal fork. A fork of the enemy king, queen, and one (or both) rooks is sometimes called a grand fork.[2] A knight fork of the enemy king, queen, and possibly other pieces is sometimes called a family fork or family check.

Game examples
Tissir vs. Dreev, 2004
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Position after 33.Qe5–f4


This example is from the first round of the FIDE World Chess Championship 2004 between Mohamed Tissir and Alexey Dreev.[3] After

 33... Nf2+ 34. Kg1 Nd3

White resigned. In the final position the black knight forks White's queen and rook; after the queen moves away, Black will win the exchange.

Soppe vs. Braga, 1998
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Position after 40.Nxe5


This example is from the ninth round of the Clarin GP Final between Guillermo Soppe and Fernando Braga.[4] After

 40... Qh1+

White resigned. The only move is 41.Ke2 which enables a royal fork with 41...Nc3+, winning the queen.

Example from an opening
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Position after 4.Nc3. Black can play 4...Nxe4 since he has a fork trick.
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After 4...Nxe4 5.Nxe4 d5, White is forked and Black will regain a piece.

In the Two Knights Defense (1.e4 e5 2.Nf3 Nc6 3.Bc4 Nf6) after 4.Nc3, Black can eliminate White's e4-pawn immediately with

4... Nxe4!

due to the fork trick

5. Nxe4 d5

regaining either the bishop or the knight.

Escaping forks

Forks can possibly be escaped. A forked piece such as the queen might check the enemy king, giving time to move the second forked piece to safety on the next move.

See also

References
  1. https://www.chess-game-strategies.com/chess-fork.html
  2. An example of a king, queen and double rook fork can be found in the 9th game in a September 2020 match between IM Eric Rosen and the Botez sisters that ended 9½-½. See Video on YouTube (Rosen's perspective) and Video on YouTube (the Botez' perspective).
  3. "Tissir vs. Dreev, Tripoli 2004". Chessgames.com.
  4. "Guillermo Soppe vs Fernando Braga, (1998)". Chessgames.com.

Bibliography

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