Discovered Attack

A discovered attack happens when a piece moves out of the way and, in doing so, reveals an attack from a completely different piece that had been blocked behind it. The piece that moves doesn't need to threaten anything itself — the entire tactic can be "free," hidden inside a move that looks routine, because the real threat comes from the piece that was standing still the whole time.

Why this is different from every other tactic on this site

Almost every other tactic is about what a piece does when it moves. A discovered attack is about what a piece stops blocking when it moves. That distinction matters for how you look for it: instead of asking "where can my pieces go that attacks something," you have to ask "which of my own pieces is currently blocking one of my other pieces from attacking something." It's a completely different scanning habit, and it's the reason discovered attacks are so often missed by players who are otherwise decent at spotting forks and pins — they're looking at the wrong piece.

Auditing your own pieces for hidden lines

The practical method: before making any move, briefly check whether the piece you're about to move is standing on a rank, file, or diagonal shared by one of your own long-range pieces (bishop, rook, or queen) and an enemy target beyond it. If it is, that move is a candidate for a discovered attack even if the piece's own destination square looks unremarkable. This is worth doing specifically with knights, since a knight's move pattern makes it easy to forget it was ever "in the way" of a bishop or rook in the first place — a knight sitting quietly on a diagonal doesn't look like it's blocking anything until you trace the line past it.

The moving piece gets to do two jobs

The strongest discovered attacks happen when the piece that moves accomplishes something useful on its own — capturing a pawn, developing with tempo, attacking a completely different piece — while the revealed attack lands on yet another target entirely. That's what makes the tactic so hard to defend against: the opponent has to deal with two separate threats that were created by a single move, and they usually only notice the obvious one (the piece that just moved) while missing the piece that was revealed behind it.

Common places discovered attacks hide

• A knight or bishop sitting on a long diagonal in front of your own rook or queen, once the center opens up.
• A pawn that's about to advance, sitting directly in front of a rook on a half-open file.
• A piece that's been developed early and never re-examined for what it might be blocking once the position has changed.

Defending against a discovered attack

Because the moving piece can be doing something else entirely, a discovered attack is genuinely hard to see coming from the defending side. The best practical defense is prophylactic: before the position opens up, check whether any of the opponent's pieces sit on a line with one of their own long-range pieces behind them, and treat that as a standing danger even if nothing is happening on that line yet. Once you've spotted the line, you can often prevent the tactic entirely just by moving your own piece off the far end of it before the discovery happens, rather than trying to react after the fact.

A discovered attack that specifically delivers check to the enemy king is important enough to have its own name — see discovered check — and it comes with sharper forcing power than the ordinary version described here, because the opponent has to answer the check before doing anything about the second threat.