Hidden passed pawn

A hidden passed pawn is not yet a passed pawn. It is usually advanced in enemy territory and blocked by an opposing pawn, but the surrounding pawn group contains a sequence that can remove that obstacle. After the transformation, the advanced pawn has no enemy pawn able to stop it on its own file or either neighboring file.

The typical mechanism uses another pawn as a decoy. That pawn advances and is offered to force the blocker to capture or move away; the pawn that appeared immobile is then released. The material given up may also let the opponent create a passer, so the idea works only when the hidden pawn is far enough advanced or wins the promotion race.

Hans Kmoch called this pawn a Sneaker. It differs from an ordinary candidate because its strength is concealed: the sequence reveals the already advanced pawn as the passer. It may grow out of a healthy majority, but the result must be verified by concrete calculation rather than assumed from a general rule.