In chess, an isolated pawn is a pawn that has no friendly pawn on an adjacent . 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 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 and associated opportunities for 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 adjacent pawns may also aid mobilization of 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 good outposts on the c- and e-file squares diagonally forward of the pawn, which are especially favourable for the player's knights. The isolated queen pawn position favours a attack, freeing both the and s due to the absence of friendly pawns on the c- and e-files. Isolated queen pawns, however, suffer from the same weaknesses as other isolated pawns. Several openings can lead to isolated pawns, such as the French Defence, Nimzo-Indian Defence, Caro–Kann and Queen's Gambit. Weakness In the endgame, isolated pawns are a weakness in pawn structure because they cannot be defended by other pawns as with connected pawns. In the diagram, the white pawn on e4 and the black pawn on a7 are isolated. Isolated pawns are weak for two reasons. First, the pieces attacking them usually have more flexibility than those defending them. Namely, the attacking pieces enjoy greater freedom to make other threats, while the defending pieces are restricted to the defense of the pawn. A defending piece is said to be "tied down" to the pawn, since it must stay rooted to the spot until the attacking piece has moved. The second reason is that the square immediately in front of the isolated pawn is weak, often providing an excellent outpost for a knight or other enemy piece, since it is immune to attack by a pawn. Also, an enemy piece on this square cannot be attacked by rooks, since the file it is on is blocked by the