The isolated pawn is basic to the problem of structural weakness. An isolated pawn is often a disadvantage because it can’t be protected by other pawns and because the square immediately in front of it can be occupied by opposing pieces. Without a friendly pawn to the side to guard the occupied square, there’s no guarantee that an obstructing enemy piece, one stationed in front of the isolated pawn under view, can be driven away. Pieces able to sit in front of isolated pawns are called blockaders, and the concept is usually referred to as the blockade.
