Check

This article uses algebraic notation to describe chess moves.

The black king is being checked by the white rook.

In games such as chess, shogi, and xiangqi, a check is an immediate threat to capture the king (or general in xiangqi). A king so threatened is said to be in check. In the following move, the player whose king is in check must get his king out of check, if it is possible. Either the threat must be stopped (by interposing a piece between the threatening piece and the king, or capturing the threatening piece) or the king must be moved to a space where it is no longer in check.

Introduction

A check is the result of a move that places the opposing king under an immediate threat by one (or sometimes two) of his pieces. (In some chess variants, check by more than two pieces is possible.) If the king is in check and there is no legal move which gets the king out of check, the king is said to be checkmated and the game is over. The player whose king is checkmated loses and the opposing player wins the game.

It is against the rules for a player to make a move which puts his/her own king in check. A king cannot directly check the opposing king himself, since this would place the first king in check. (All other types of pieces can check.) A king can make a move which exposes the opposing king to a discovered check.

In this usage, the words "check" and "chess" come via Arabic from Persian shāh, meaning "king".^[1]

Getting out of check

White is in check. He can get out of check by three methods.

There may be up to three possible ways to get a king out of a single check on the following move:

• Capturing the checking piece, with either the king or another piece. If the checking piece is on a square next to the king, the king can capture the piece if the king does not move into a new check, i.e. if the piece is not protected by another enemy piece.
• Moving the king to an adjacent square where it will not be in check. The king is not allowed to castle when it is in check. The king may capture an enemy piece in a move to get out of check, as long as the piece is not protected.
• Blocking the check. This will only work if the checking piece is a queen, rook, or bishop and there is at least one empty square in the line between this checking piece and the checked king. Blocking a check is done by moving a piece (from the checked king's army) to a square in line in between the checking piece and the checked king. The blocking piece is then absolutely pinned to the king by the attacking piece (until it is unpinned).

In the position in the diagram, White can get out of check by three methods:

1. The move Nxa2, capturing the attacking piece
2. Moving the king to any unattacked square (marked with "x"), i.e. Kd6, Ke5, or Ke7.
3. Blocking the check by the move Rc4 or Nd5.

If a king is placed in double check, the king must get out of both checks on the following move. Since it is impossible to capture both checking pieces or block both lines of attack in a single move, a double check can be escaped only by moving the king out of check. The king may, however, capture one of the checking pieces in the process, if that piece is adjacent to the king and not protected by another piece.

If none of these possibilities can get the king out of check, then it is checkmated and the game is won/lost.

Types of checks

A simple and very common type of check is when a piece moves to directly attack the opposing king only by itself. Sometimes such a check is part of a chess tactic such as a fork, a skewer, or a discovered attack on another piece. In some cases, a check can be used to defend against such tactics.

There are also a few more special types of check:

• Discovered check - A discovered check is similar to any other type of discovered attack except that it is a discovered attack on the opposing king. In a discovered check, a piece moves out of the line of attack by another piece so that this other piece (which can be a queen, rook, or bishop) is then checking the opponent's king. The piece that actually moved in the discovered check move could possibly be any type of piece belonging to the same player as the checking piece except queen or the same type of piece administering the check. A discovered check could be a tactic in itself because the piece that moved could attack or otherwise create a threat to another piece on the checked king's side. The opponent has to get out of the discovered check on the following move and may not get a chance to thwart the attack by the other piece that moved.
• Double check - A double check is when two pieces check the opponent's king on the same checking move. This happens when the piece that moved during the checking move attacks the king and another piece checks by discovered check on the same move. It can also happen, though very rarely, when an en passant capture opens two lines of attack simultaneously. In algebraic chess notation, a double check move is sometimes noted with a "++" after the written move in place of the usual "+", although sometimes "++" has been used to indicate checkmate in more modern literature (see here). When "++" is used to indicate double check, "#" is used to indicate checkmate, but using "++" for double check is obsolete.
• Cross-check - In chess, when a check is answered by a check, particularly when this second check is delivered by a piece blocking the first, it is termed a cross-check. In fact, a "cross-checkmate" is also possible in that way (that is, to answer a check with a checkmate) but since no such term exists, it would fall under the definition of cross-check as well. Cross-checks are rather rare but are a popular theme in chess problems.

Notation and announcing check

In algebraic chess notation, a checking move is noted like any other move, except that a "+" is written after the move.

In friendly games, the checking player customarily says "check" when making a checking move. Announcing "check" is not required under the rules of chess and it is usually not done in formal games. Less commonly (and obsolete), the warning garde can be said when a player directly attacks the opponent's queen in a similar way. This was mostly abandoned in the 19th century (Hooper & Whyld 1992:74). The same move can be both check and garde simultaneously. Before the queen acquired its current move (about 1495) the rook was the most powerful piece. At that time the term check-rook was used for a move that checked the king and attacked a rook at the same time (Hooper & Whyld 1992:75).

Checking in tactics and strategy

Sometimes checking an opponent provides no benefit to the checking player. This is called a "useless check" and it may even provide the checked opponent with a tempo (move opportunity) to move his king into a safer position (Hooper & Whyld 1992:437). However, there are many times when checking the opponent's king may be a useful tactic or part of a tactic, either in attacking or in defense. Checking is often used in combinations with many other tactics or simply to force an opponent into a position where the opposing king can be checkmated, otherwise taken advantage of, or is otherwise worse for the opponent. Some attacks involves numerous checks to force an opponent into a losing position, especially when the king is exposed. An unexpected check in a forced combination or an overlooked cross-check in a planned series of checks may serve as sort of a zwischenzug, foiling the plan.

Some uses of checking:

• Repetitive checking to prevent losing a game going poorly (perpetual check)
• Royal fork (knight fork of king and queen) or other forks involving the king.
• Checks to force an exchange.
• A double check could be especially bad for the opponent since there are likely to be fewer options to get out of check. A double check is often more likely to lead to checkmate or loss of material.
• A check might force a king to move so that it cannot castle later.
• Moving a piece to give check can sometimes open a line of attack on another piece. The opponent must escape the check, and therefore cannot (in general) prevent the other piece from being captured (discovered attack).
• Similarly, the piece moved to create a discovered check may attack another enemy piece, leading to the same scenario.
• The king may also, by being forced to move out of check, enable the checking piece to capture another piece (an absolute skewer).
• A check might force some piece to block it and therefore pose an absolute pin on that piece.
• A check might deflect the king from protecting some other piece (particularly in an endgame, to capture opponent's pawns).

See also

• Rules of chess
• Checkmate

Notes

References

• Hooper, David; Whyld, Kenneth (1992), The Oxford Companion to Chess (second ed.), Oxford University Press, ISBN 0-19-866164-9 
• Golombek, Harry (1977), Golombek's Encyclopedia of Chess, Crown Publishing, ISBN 0-517-53146-1 
• Just, Tim; Burg, Daniel B. (2003), U.S. Chess Federation's Official Rules of Chess (fifth ed.), McKay, ISBN 0-8129-3559-4 
• Schiller, Eric (2003), Official Rules of Chess (second ed.), Cardoza, ISBN 978-1-58042-092-1