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