Poisoned pawn
A poisoned pawn is a pawn that can be captured, but whose capture lets the opponent punish the greedy player with a tactic that costs more than the pawn is worth.
The pawn looks free, and that is exactly the trap. It may be undefended or lightly defended, yet taking it pulls a key piece away from its job. The punishment might be a mate, a trapped queen, or a loss of a larger piece.
The habit that guards against it is asking one question before every capture: what changes if this piece leaves its square? A rook that guards the back rank, a queen that holds an escape route, or a knight that blocks a line can all be dragged away by a tempting pawn. If the capture removes the last defender of something important, look for the refutation before moving.
As the player offering the pawn, you need the follow-up to be forced. If the capture turns out to be safe after all, you have simply given away a pawn. Calculate the line to the end, including the replies that decline it. Takers usually go wrong by checking only whether the pawn is attacked, not what the capturing piece stops protecting. A pawn up is no comfort if the game ends two moves later.
A neighboring idea is Trapped piece. A trapped piece cannot reach safety: every square it might retreat to is covered, blocked or ruinous, so once it is attacked the owner will lose it for little or nothing.
A neighboring idea is Hanging piece. A hanging piece is a piece that is attacked by the opponent and has no defender, so it can be captured for free unless its owner moves it, defends it or makes a bigger threat.
To see how often "Poisoned pawn" or a pattern like it decides your own games, book a first lesson: George Li reviews your games and writes a study plan around what he finds.
Related terms
A back rank mate is a checkmate on a player's first or eighth rank, typically by a rook or queen, delivered when the king's own pawns leave it no square to step to.
Deflection is the tactic of dragging an enemy defender off its post, often by a threat or an offered capture, so that what it was holding together falls apart.
A decoy is a tactic that lures an enemy piece onto a chosen square, usually with a sacrifice it has to accept, so that the piece can be forked, blocks one of its own lines or loses its old job.
A trapped piece cannot reach safety: every square it might retreat to is covered, blocked or ruinous, so once it is attacked the owner will lose it for little or nothing.
A hanging piece is a piece that is attacked by the opponent and has no defender, so it can be captured for free unless its owner moves it, defends it or makes a bigger threat.
A sacrifice is a deliberate decision to give up material, such as a pawn, an exchange or a piece, in return for something else, like mate, a stronger attack, a better structure or a larger gain later.
Guides that go further
What to decide first, the questions to ask, what a first lesson should show and the red flags to avoid.
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A game review, a read on your level and a written study plan from George Li.
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A first lesson starts with your games: George reviews them and builds a study plan around what he finds.