Passed Pawns
A criminal that must be kept under lock and key
A passed pawn is a pawn with no enemy pawn in front of it (on its own file or either adjacent one) between it and promotion. Nothing but pieces can stop it, and pieces hate the job. Every endgame plan begins with the question: who has the passer, and who has to babysit it?
Play this ending (free)The square rule: catch it or don't bother
The instant test for a footrace between king and passer: build the square of the pawn: one corner on the pawn, the diagonal running to the promotion rank, and the box completed from there (for the a4-pawn above: a4–a8–e8–e4). If the defending king, on its move, stands inside the square or can step in, it catches the pawn. Outside, it never will; don't waste the moves.
Two footnotes worth points: a pawn still on its starting square gets a two-square first step, so build the square as if it stood one rank further; and check the king's path for obstacles: a square-rule “catch” fails if the king's diagonal route is blocked by its own pawn or bends around your king.
The outside passed pawn
In king endgames, the outside passed pawn, the passer furthest from the main pawn mass, is one of the most reliable wins in chess, and it wins by dying. The plan: push it. The defending king must trek to the rim to stop it; the moment he arrives, you let him have it, and your king turns and devours the abandoned pawns on the other side. The passer costs one pawn and buys the whole board.
The same decoy logic ranks all passers: the further your passed pawn stands from the main theater, the more of the defender's attention it hijacks. Its close cousin, the protected passed pawn (guarded by a neighbor pawn), doesn't even need to run: it paralyzes the enemy king forever, since taking the guard or leaving the square both lose on the spot.
Handling passers: both sides of the argument
With the passer: passed pawns must be pushed: every rank gained multiplies the decoy pressure and shrinks the defender's square. Support it from behind with rook or king; in rook endings, remember the rook belongs behind its passer.
Against the passer: blockade first. Park a piece, ideally the king or a knight, directly in front of the pawn; a blockaded passer is a wall your opponent built for you. Then keep the square rule arithmetic alive on every move: each pawn trade and king step changes whether you still catch the runner. Endgames are lost in one careless tempo of forgetting to recount.
Questions
What is a passed pawn?
A pawn with no enemy pawn ahead of it on its own file or the two adjacent files. Nothing can stop it by pawn means; only enemy pieces or the king can prevent its promotion.
What is the square of the pawn rule?
A visual shortcut for the king-versus-pawn race: form a square with one corner on the pawn and the far side on the promotion rank. If the defending king is inside the square (or enters it on its move), it catches the pawn; otherwise the pawn promotes. Remember the two-square first move of unmoved pawns.
How do you stop a passed pawn?
Blockade it: plant a piece, ideally the king or a knight, directly on the square in front of it, and in rook endgames put your rook behind it. A blockaded passer stops being a threat and becomes a fixed weakness to attack.
Why is an outside passed pawn so strong?
Because it wins as a decoy: the defending king must leave the main pawn mass to stop it, and the attacking king invades the abandoned side. The pawn itself is usually given up, in exchange for every other pawn on the board.
Don't just read it, play it
Every position below is playable right now, free, no signup, against a tablebase-perfect opponent that never gives up and explains every mistake.
The Square of the Pawn
Black to play and draw
The Outside Passed Pawn
White to play and win
Winning the Pawn Race
White to play and win
Rook vs Advanced Pawn
White to play and win
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