Explanation

The following diagram illustrates discovered checks. A white rook points on the open e-file toward the black king. White's bishop on e4 is preventing the check. If the bishop moves, it discovers a check by the rook:

The bishop has a "free" move, because Black has to deal with the rook check first and can't immediately react to the bishop's discovering move.

A discovered check can be especially strong if the discovering move is a forcing move, for example a capture, or an attack. In that case, the opponent often cant recaptur, or defend the attack piece and defend against the discovered check at the same time. Let's look at the possible discovered checks by White in this diagram:

• 1.Bd3+? and 1.Bd5+? don't use the free bishop move effectively, as the bishop does not capture or threaten anything. Black can defend against the check with, for example, 1...Be7.
• 1.Bxg6+ uses the free move to capture the knight. White wins the knight, because Black can't recapture and defend against the check at the same time.
• 1.Bf5+ uses the free move to attack the queen. Black must defend against the check and can't save the queen.
• 1.Bxb7+ captures a pawn, attacks the queen and the rook, and gives check. Black again can't defend against all of those threats
• The best move is actually 1.Bc6+! The bishop gives check and discovers a check from the rook, so the king is in check from two directions at once! This is called a double check. Double checks can't be blocked, and the king is forced to move: 1...Kd8 2.Re8# is opera mate.

Examples

Black can win with the discovered check 1...Bc3+.
The rook on e8 gives check, and the bishop on c3 attacks the rook on b4.
White is unable to defend against both threats with one move. Note that 2.Re4 doesn't defend against both threats here, as the rook is unprotected on e4.

Because your opponent has to deal with the check first, the discovering piece gets a free move, and can move to an otherwise inaccessible protected square, as in the following example:

White can win with the discovered check 1.Na7+.
The queen on b5 gives check, and the knight on a7 attacks Black's queen.
Black cannot defend against both threats at the same time. 1...Rxa7 is an illegal move as it would leave the king in check. 1...Qc6 doesn't help as the queen is insufficiently protected on c6.

How to spot a discovered check

You can compare a discovered check with a fork where you attack a piece and give a check. For this kind of fork, one piece attacks and checks. With a discovered check, one piece attacks, and another piece gives check.

Whenever a possible check is blocked by one of your own pieces, think about ways to move that piece and make a discovered check. Your opponent will have to deal with the discovered check first. You get a free move with the discovering piece, and can consider possible sacrifices. With some practice, you will be able to spot blocked checks quickly and grab your chance if a discovered check is possible!

Related motifs

A discovered attack is a move by one piece that reveals an attack by another piece.