Rook vs Pawn: The Intermediate Check

Watch the method: press play to see the winning idea run, or step through it move by move.

Rook against a passed pawn is decided by tempi, and a check is the cheapest tempo on the board.

Only Rf8+ wins. Not Rg8, not a king move, nothing else. The rook checks first, the black king is pushed off the f-file, and only then does the rook take up its post.

Then block. Rg8 stops the g-pawn dead. The whole point of the check was to reach this square with the enemy king a step further away.

Never trade the rook for the pawn. Rxg4 Kxg4 leaves two bare kings. The rook stops the pawn, the king wins it.

Why an intermediate move. An intermediate check gains a tempo only if it forces a reply. Here it does, and that single free move is exactly the margin between winning and drawing.

Check with a purpose, not by reflex. A check only earns a tempo when every reply worsens the defender's king. If he can answer by stepping to a better square, closer to the pawn or in front of it where he blocks his own runner, the check gave the tempo away instead. And when you are defending: keep the king behind the pawn, never ahead of it, so no check ever finds you on a square you regret.