The Rule of the Square and Its Exception
White to play and win, after Bianchetti
PlayThe rule of the square says the black king catches your a-pawn: it stands on f3, comfortably inside. It still cannot stop the pawn, and the reason is that its own pawns are in the way.
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Inside the Square and Still Too Slow
White to play and win · Win against perfect defense
Waking the engine…
The theory
Watch the method: press play to see the winning idea run, or step through it move by move.
Check it honestly. The square of the a2 pawn is a2-a8-g8-g2, and the black king on f3 is inside it. Push straight away and he does catch it: 1.a4? Ke4 2.a5 Kd5 and the pawn is stopped.
The rule of the square is a shortcut: draw the square whose side is the path from the pawn to its promotion rank, and if the enemy king cannot get inside it, the pawn queens by itself.
The exception. The rule quietly assumes the king has a clear road. When its own pawns occupy the squares it needs, the king can be inside the square and still too slow. Bianchetti showed this in 1925.
The deflection. 1.d5! is the only move. Black takes with 1...exd5 and his pawn now blocks d5. Then 2.a4! (again the only move), and after 2...Ke4 3.a5 the king would love to play Kd5, but the square is taken by his own pawn.
In this drill the defender never stops racing. Play the deflection first, then run.
Keep going
Stop the Runner First, Then Queen
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Mined Squares: c4 and b6
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Winning with a Frozen King
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All 68 king & pawn positionsFollow the full curriculum (free)