// If the pawn is passed, isolated, or member of a pawn chain
// it cannot be backward. If can capture an enemy pawn or if
// there are friendly pawns behind on neighboring files it cannot
// be backward either.
// If the pawn is passed, isolated, or member of a pawn chain
// it cannot be backward. If can capture an enemy pawn or if
// there are friendly pawns behind on neighboring files it cannot
// be backward either.