A poisoned pawn is a pawn deliberately left capturable because taking it costs the grabber dearly in time, position, or a trapped piece, most often a queen that strays to win it.
Not every free pawn is free. A poisoned pawn is bait: the capture is legal and wins material, but the price is hidden in what happens next, such as a queen dragged offside and hunted for tempi, files opened straight at your own king, or a piece that never gets home. The b2 and b7 pawns are the classic victims, since an early queen grab there strays far from the action.
The most famous example carries the name: the Najdorf Poisoned Pawn, where after 6.Bg5 e6 7.f4 Qb6 8.Qd2 Black plays Qxb2 anyway. Decades of analysis, with Fischer as the line's great champion and Spassky-Fischer 1972 among its landmark games, hold that Black survives with precise play, but a single wrong step leaves the queen trapped or the defense overrun. The French Winawer has its own poisoned pawn line with colors reversed, where White's queen raids g7.
The practical rule: before grabbing a pawn with your queen in the opening, count the tempi you will lose to threats against her and ask what your opponent's lead in development buys during those moves. If you have not checked the concrete lines, decline politely and finish developing. If you set the trap yourself, remember a poisoned pawn only works when the compensation is real.
Because eating it can be fatal. The pawn stands undefended on purpose: capturing it drags a piece, usually the queen, away from the center, and the time spent extracting her hands the opponent a dangerous lead in development or a direct attack.
Modern theory and engines say yes: with exact play Black holds the extra pawn or returns it for equality. The catch is the word exact, since the resulting positions are among the sharpest in all of opening theory, which is why it is a specialist's weapon.
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