Check (chess) - Types of Checks

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 a check from two pieces to the opponent's king in a single move. This happens when a moved piece attacks the king, resulting in a second piece giving check by discovered check. 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 "++" has been used to indicate checkmate (along with "#"). A double check cannot be blocked, nor can it be met by capturing one of the checking pieces (unless the king itself makes the capture), because there is check from two directions.

• Cross-check – 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.