Doubled pawns are two pawns of the same colour placed on the same file after a capture has occurred. For instance, if White has pawns on both e3 and e4, those are doubled pawns on the e-file.
This pawn structure is generally considered a structural weakness: the two pawns cannot protect each other (unlike adjacent pawns), the leading pawn advances at the cost of exposing the one behind, and the shared file can become an easy target for the opponent’s rooks once opened. In endgames, doubled pawns often struggle to create a passed pawn or provide adequate king support.
In practice, doubled pawns should not always be avoided at all costs. They frequently come with concrete compensation: an open file for a rook, the bishop pair, or a development advantage. The key question is whether the dynamic or material gain outweighs the structural cost.
