Isolani

In chess, an isolated pawn is a pawn that has no friendly pawn on an adjacent file. Isolated pawns are usually a weakness because they cannot be protected by other pawns. The square in front of the pawn may become a good outpost or otherwise a good square for the opponent to anchor pieces. Isolated pawns most often become weaker in the endgame, as there are fewer pieces available to protect the pawn.

Isolated pawns can, however, provide improved development and associated opportunities for counterplay that offset or even outweigh their weaknesses. The files adjacent to the isolated pawn are either open or half-open, providing two lanes of attack for the rooks and the queen. The absence of pawns adjacent to the isolated pawn may also benefit the player's knights and bishops.

An isolated pawn on the d-file is called an isolated queen pawn or simply an isolani. In addition to the open or half-open c- and e-files, the isolated queen pawn can provide a good outpost on the c- and e-file squares diagonally forward of the pawn, which are especially favorable for the player's knights. The isolated queen pawn position favors a kingside attack, freeing both the light and dark-squared bishops due to the absence of friendly pawns on the c- and e-files. Isolated queen pawns suffer, however, from the same weaknesses as other isolated pawns.

Many "textbook" openings lead to isolated pawns, such as the French Defence, Nimzo-Indian Defence, Caro–Kann and Queens Gambit.

In the endgame, isolated pawns are a weakness in pawn structure because they cannot be defended by other pawns as with connected pawns. In this diagram, the white pawn on the e4-square and the black pawn on a7 are isolated.

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