Mastering Discovered Attacks: Two Threats in One Move
Contents
The pin and the skewer exploit an alignment of enemy pieces. The discovered attack flips the perspective: it is an alignment of YOUR pieces that strikes. Your long-range piece stays still, lying in ambush; a piece of yours, placed in front of it, steps aside and unmasks the attack. The effect is devastating, because the move produces two simultaneous threats — the moving piece’s own and the unmasked piece’s — and the opponent can only parry one. It is the richest of the line tactics, and the one that demands the most craft: this lesson takes it apart piece by piece.
The mechanics: a screen piece and an ambush piece
Every discovery rests on a battery of two of your pieces in line: behind, a long-range piece — bishop, rook or queen — whose line is obstructed; in front, a screen piece doing the obstructing. As long as the screen does not move, the battery sleeps. The moment it steps aside, the ambush piece strikes.
What separates the discovery from the pin and the skewer fits in one question: who moves? In the pin and the skewer, your attacking piece places itself on the line. In a discovery, your attacking piece does not move — it is the screen that withdraws.
The motif’s power comes from the double threat. The screen piece does not merely clear the line: it plays its own move, with its own threat — a capture, an attack, a check. At the same instant, the unmasked piece creates a second one. Two threats, one enemy move to answer them: the arithmetic is merciless.
Rank the motif’s forms. The simple discovered attack creates two ordinary threats. The discovered check turns one of them into a constraint: one of the two threats is a check, which the opponent must answer first. The double check, finally, is the absolute form: the screen AND the unmasked piece give check together — no interposition, no capture can parry two checks at once, and only the king may move.