Discovered attacks and double check
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Most tactics are about one piece doing something forceful: a knight forking two pieces, a bishop pinning a knight to its king. A discovered attack is different. The piece that moves is not the one that attacks. Instead, moving it opens a line for a rook, bishop or queen standing behind it, and that hidden piece delivers the blow. The result is two threats from one move: whatever the moving piece does, plus the new attack from the piece behind it. When the hidden attack is a check, the tactic becomes one of the most powerful in chess.
The examples below were checked with a chess rules library, including the lists of legal replies quoted in the text. Our article on forks, pins and skewers covers the other common double-attack tactics; this one adds the discovered family.
How a discovered attack is built
Every discovered attack needs three pieces in a line: the long-range piece at the back (rook, bishop or queen), the piece in front of it that will move out of the way, and the target at the far end. Before the move, the line is blocked by your own piece, so the target looks safe. After the move, the line is open.
The strength comes from what the front piece does when it moves. If it simply steps aside, the opponent can move the target away and nothing is gained. If it moves with a threat of its own, especially a check or a capture, the opponent has two problems and only one move to solve them.
Example 1: a bishop check uncovers the rook
The queen on e8 is lined up with the white rook, but the bishop on e4 is in the way. White moves the bishop off the file with a capture and a check: Bxh7. Now the black king is in check, and at the same time the rook on e1 attacks the queen.
1.Bxh7+ Kxh7 2.Rxe8
Black has exactly three legal replies, all king moves, and none of them saves the queen. White gives up a bishop and wins a queen and a pawn. Notice what made it work: the bishop's move was itself forcing. Had the bishop moved to a quiet square such as d3, Black would simply have moved the queen.
Example 2: discovered check
A discovered check is a discovered attack in which the hidden piece attacks the king. It is especially strong because the piece that moves can go almost anywhere, even to a square where it can be captured, and the opponent still has to deal with the check first.
1.Nc6+ Kd7 2.Nxa7
When the knight jumps to c6, the rook gives check along the e-file and the knight attacks the queen on a7. Black's only legal moves are Kf8 and Kd7: no piece can block the file, because the pawn on d4 shuts the queen's diagonal and Black's own pawn on b7 shuts the rank. Taking the knight with bxc6 is not allowed, as it does nothing about the check. The king moves, and the queen falls.
This is the point to remember about discovered checks. The front piece is free for one move. It can capture anything it reaches, and the opponent cannot recapture or move the attacked piece because the king must be dealt with first.
Example 3: double check
A double check happens when the piece that moves gives check itself and also uncovers a check from the piece behind it. The king is then attacked by two pieces at once. A single check can be answered in three ways: capture the checking piece, block the line, or move the king. Against a double check, capturing one attacker leaves the other, and blocking one line leaves the other. Only a king move can help. That is why double checks so often end games.
The most famous example is the game between Richard Réti and Savielly Tartakower, played in Vienna in 1910. White sacrificed the queen to drag the king into a double check.
1.e4 c6 2.d4 d5 3.Nc3 dxe4 4.Nxe4 Nf6 5.Qd3 e5 6.dxe5 Qa5+ 7.Bd2 Qxe5 8.O-O-O Nxe4 9.Qd8+ Kxd8 10.Bg5+
After 9.Qd8+ Kxd8, the white bishop moves from d2 to g5. The bishop itself attacks d8, and moving it opens the d-file for the rook on d1. Black's king is in check from two pieces and has only two legal moves, Ke8 and Kc7. After Kc7 the bishop goes to d8 and it is mate; after Ke8 the rook goes to d8, also mate.
10...Kc7 11.Bd8#
Look at Black's position before the queen sacrifice. Black had more material, but the king was still in the centre and the d-file was open. Those two facts, not any single blunder, made the combination possible.
How to spot discovered attacks in your games
- Look for your own pieces in front of your long-range pieces. A rook behind a knight, a bishop behind a pawn, a queen behind a bishop: each is a loaded weapon if the line leads to something valuable.
- Check where the line leads. Follow the file, rank or diagonal past your front piece. If it reaches the enemy king or queen, or an undefended piece, there may be a discovered attack.
- Make the front piece's move count. The best discovered attacks combine the hidden threat with a check, capture or second threat from the piece that moves.
- Watch your own lines too. The same pattern works against you. If your king or queen stands on a line with an enemy rook, bishop or queen, with only one enemy piece between them, that piece may be about to move with a threat.
Discovered attacks are rarer than forks and pins in beginner games, which is exactly why they win so much material when they appear: few opponents look for them. Set up the three examples on a board and play them through, then look for the same alignments in your own games.