The Discovered Attack

A discovered attack is what happens when you move one piece and reveal an attack from a second piece that was standing behind it. The moving piece makes its own threat, the unveiled piece makes another, and your opponent gets exactly one move to deal with both. Usually that is not enough.

The anatomy

Every discovered attack has three parts: the battery (a bishop, rook, or queen aimed down a line), the screen (your own piece standing in the way), and the unmasking move (the screen steps aside). The magic is that the screen does not have to move anywhere useful for the battery. It moves wherever it hurts the most, because the piece behind it does the heavy lifting either way.

That is what makes discoveries nastier than forks. In a fork, one piece has to attack two things by itself, so the geometry is strict. In a discovery, the front piece is temporarily free. It can capture something, attack the queen, or give a check of its own, and the battery still fires. The front piece is functionally invincible for one move: capturing it does nothing about the attack behind it.

Discovered check

When the unveiled piece attacks the enemy king, you have a discovered check. Now the front piece has a full turn of total immunity. It can grab a defended pawn, a defended rook, even sit on a square covered by three pieces, because your opponent is legally required to answer the check first. A knight that unveils a bishop check can eat its way across the board and come home fat.

Double check

The special case that ends games: the front piece ALSO gives check as it unveils the second one. Two checks from two different pieces at the same time. Blocking answers one check but not the other. Capturing removes one checker but not the other. There is exactly one kind of move that can answer both at once: the king moves. That is the whole rule, and it is why double check is the most forcing move in chess. If the king has no safe square, the game is simply over, regardless of how much material is hanging or how many defenders are standing around looking useful.

Spotting and building them

Scan for any bishop, rook, or queen of yours that has one friendly piece between it and something juicy: the enemy queen, a rook, the king. That piece in the middle is a loaded spring. Then ask the only question that matters: where does the front piece go to cause maximum damage on its own? Knights make the best screens because their exit squares are weird and hard to cover. If you do not have a battery yet, build one. Sliding a rook or bishop behind a knight is a quiet move that creates a threat your opponent often cannot see.

How to avoid being the victim

Treat any enemy line piece pointed at your queen or king as loaded, even with a piece in the way. Especially with a piece in the way. The blocked line is the trap; players relax because “the bishop isn’t doing anything.” It is doing something. It is waiting. When an enemy piece stands between a slider and your big material, calculate every square that piece can jump to before you assume you are safe.

The classic

Torre versus Lasker, Moscow 1925: the famous windmill. Torre’s bishop sat on f6, aimed at the black king. His rook captured on g7 with check, then lifted off g7 again with discovered check from the bishop, grabbed a piece, returned to g7 with check, lifted again, grabbed another. The rook toured the seventh rank devouring material, and Lasker, a former world champion, could do nothing but shuffle his king back and forth and watch. One battery, one screen, half an army gone.