Changes

In the terminology used by [[Hans Kmoch]] <ref>[[Hans Kmoch]] ('''1959, 1990'''). ''Pawn Power in Chess''. New York: Dover, 1990. Previous ed.: New York: McKay, 1959. ISBN 0-486-26486-6</ref>, a '''Sentry''' is a [[Pawn|pawn]] controlling the [[Squares|square]] lying on the path or [[Pawn Spans|front span]] of an opponent's pawn, thereby preventing it from becoming a [[Passed Pawn|passed pawn]] <ref>[https://www.chess.com/forum/view/chess-equipment/pawn-power-in-chess-by-hans-kmoch-glossary-of-terms Pawn Power in Chess by Hans Kmoch - Glossary of Terms - Chess Forums] - [https://en.wikipedia.org/wiki/Chess.com [Chess.com]]</ref>.