Discovered Attack Explained. Stepping Aside to Strike
You followed the bishop. Understandable, it was the one moving. But the rook behind it just became dangerous without moving at all. That is a discovered attack, one of the most useful tricks in chess. This page shows how it works and how to use it.
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The idea. Move the blocker
In chess, a discovered attack happens when one piece moves out of the way, revealing an attack from another. The setup has three parts. A long range piece, such as a rook, a bishop or a queen. A friendly piece blocking its line. And an enemy target beyond the blocker. Move the blocker, and the hidden attack becomes a direct threat.
The important question is where the blocker goes. It can step aside quietly, or it can do something useful on the way. If it makes a threat of its own while it opens the line, one move creates two problems.
One move, two jobs
Here the bishop leaves the file with check. At the same moment the rook's attack opens, so Black faces two threats and one of them demands an answer right now.
Black cannot simply rescue the rook and ignore the king. In this particular position there is no way to block the check or to capture the bishop, so the king has to move. Once it does, the white rook takes the black rook. The bishop did two jobs. It cleared the file and it forced Black to spend a move on the check. That is why its destination mattered.
Be careful with a simpler version. If the bishop only attacks a queen and the rook attacks a rook, that does not automatically win material. Sometimes one reply solves both problems. Always check the captures, the escapes and the counterattacks, because a clever looking move needs a real payoff.
Discovered check. The piece behind gives the check
There is a closely related idea called discovered check. The difference is which piece gives the check. In the last example the moving bishop gave check. In a discovered check the piece behind it gives the check, and the moving piece is free to do something else.
Here the bishop captures the black rook on h8. That uncovers check from the white rook, so Black must answer the check, and the bishop has already collected something. Before choosing such a move, check that Black cannot answer the check and recover the material.
Double check. Two pieces at once
Ready for the bigger surprise? Change the bishop's destination again. This time it attacks the king while uncovering the rook's attack on that same king. Two pieces give check at once. That is a double check.
Against a double check the only legal reply is to move the king. Blocking one attack leaves the other, and capturing one attacker with another piece leaves the other too. The king needs a safe square, or it is checkmate.
How to defend against it
Notice the lineup before it opens. You might move the target, interrupt the line, or remove the blocking piece if the resulting position is safe. Always check what becomes exposed when you move.
When your opponent moves a piece, look again at the square it left. The surprise might be behind it.
The pattern to remember
- Find the piece behind the blocker.
- Find its target.
- Ask what the blocker can accomplish by moving. A check or a capture makes the discovery much stronger.
Sometimes stepping aside is how you make your biggest impact. For a close cousin of this idea, read how pins, skewers and x-rays use the same lines.
Watch Discovered Attack in motion
The same ideas as an animated video, once as the full lesson and once as a 45 second teaser.
The three and a half minute version. The same lesson as an animated video. Watch on YouTube
The 45 second version. Watch on YouTube
Sources for Discovered Attack
- The positions shown are simplified teaching positions, each checked with a chess program.
- Chess.com, Discovered Attack