Perpetual check — the only rescue for the weaker side

Draw Black to move · Queen endgames · Difficulty about Elo 1500

The plan

In the queen endgame the eternal check series is the standard rescue for the weaker side — but it is not a stopgap, it is a technique with a clear condition. The right check is always the one that also keeps an eye on the queening square; all the others give the opponent a free move and lose. In the starting position this is brutally clear: of twenty-five moves exactly one holds, and even after that the defender repeatedly faces a position with exactly one correct move. The mechanism behind it is easy to remember. The queen looks for a diagonal that runs through the queening square, and swings back and forth on it: sometimes with check, sometimes quietly, but never in a way that leaves the diagonal. Two things are forbidden — capturing the pawn while it is defended by the king, and giving some pretty check that gives up the coverage. And when the opponent offers the queen, it is taken: queen against queen is a draw, even if a pawn promotes.

Rule of thumb: perpetual check only saves you if every check also covers the queening square — a check into the blue loses.

Why this level: Perpetual check as the only rescue; exactly one move holds

The solution, move by move

1. 1… Qd6+ The ONLY move that holds — twenty-four lose. The queen goes with check onto the diagonal that runs through the queening square. Capturing the pawn costs the queen (first sideline).
   Sideline 1… Qxb7+ Greed: the pawn is the whole danger, so away with it — and even with check. 2. Kxb7 It was defended by the king. Queen against bare king, lost.
2. 2. Ka8 The king dodges; it has three squares, all equally good.
3. 2… Qd5 Again the ONLY move, and this time without check. The queen stays on the diagonal and from there covers the square on which the pawn wants to become a queen. The obvious check from the back rank loses at once (second sideline).
   Sideline 2… Qd8+ The check from the back rank covers the queening square too, after all — it looks just as good as the quiet move of the main line. 3. b8=Q Except White promotes anyway, since he still has his first queen. 3… Qxb8+ Black has to take, 4. Kxb8 and the king recaptures. One queen against a bare king — lost. The quiet move in the main line covers the same square without offering its own queen.
4. 3. Ka7 White tries it with the other square.
5. 3… Qc5+ And again the ONLY move — the same diagonal, one square further, again with check.
6. 4. Ka8
7. 4… Qd5 The ONLY move. You can see the pattern: the queen lives on this one diagonal and never leaves it.
8. 5. Qd4+ The best try White has: a check that attacks the black queen at the same time.
9. 5… Qxd4 The ONLY move — and it is easy to miss because it looks so harmless. Dodging costs the queen (third sideline).
   Sideline 5… Kg3 Dodging the check is the natural reflex — and a mistake here. 6. Qxd5 Because the check was also an attack on the queen. Taking was compulsory, however inconspicuous it looked.
10. 6. b8=Q The ONLY move that still keeps White in the draw. The pawn must promote at once, otherwise the black queen catches it.
11. 6… Qd5+ Queen against queen. Black keeps giving check and needs nothing else at all any more.
12. 7. Ka7
13. 7… Qa2+ A draw. The pawn has indeed become a queen — that changes nothing, because both sides now have the same thing.

More in Queen endgames

• Queen and pawn against queen — the knight pawn jams Draw
• Queen against two bishops — won, but not within fifty moves White wins
• Queen and pawn against queen — the rook pawn isn't enough Draw
• Queen against two knights — the king step decides White wins
• Queen and pawn against queen — the bishop pawn wins White wins
• Queen against rook and bishop — both on a knife's edge Draw