Something Given Back

Against an opponent rated more than two hundred points higher, Cios reached a won king-and-pawn endgame — and then, with the full point there for the taking, let it slip. A study in how little room for error a winning pawn ending leaves.

Notes by Tilburg Chess Notes

AnalysisStockfish 18, depth 30 per position, four candidate lines per move. Evaluations in pawns from White’s perspective; marks and assessments are the engine’s.

☛ Tap any move — or any board — to open the interactive board. It pins to the top and follows along; ←/→ step, × closes it.

1.e4 c5 2.Nf3 a6 — The O’Kelly, a flexible Sicilian sideline that invites White to commit first.¹ 3.c3 d5 4.exd5 Qxd5 5.d4 e6 6.Be2 Nf6 7.O-O Be7 8.dxc5 Bxc5 9.Qxd5 — The queens come off before the middlegame has properly begun — a clean, technical day in prospect rather than a sharp one. 9…Nxd5 10.Nbd2 — White is a shade better.

10…O-O 11.Ne4 Be7 12.c4 Nf6 13.Nxf6+ Bxf6 14.Rb1 Nc6 15.b3 Rd8 16.Bb2 Bxb2 17.Rxb2 e5 18.Rd1 — The pieces come out, and the heavy pieces line up on the d-file — over the next few moves they all come off.

18…Bf5 19.Rbd2 f6 20.Rxd8+ Rxd8 21.Rxd8+ Nxd8 — The rooks are gone. A level minor-piece endgame, bishop and knight apiece.

22.Nd2 Kf8 23.Bf3 Ke7 24.Ne4 Bxe4 25.Bxe4 — The last minor pieces head for the door; if anything Black’s knight is the happier piece here.

25…h6 26.Bd5 Kd6 27.b4 Nc6 28.Bxc6 bxc6 — And now it is a pure king-and-pawn ending, dead level. White’s only winning try is to fix the queenside and manufacture a passed pawn.

— What follows is one idea, missed three times. Everything here turns on a single pawn break — …f5 for Black, f3 for White — and over three moves each player reaches for a natural king or pawn move instead of that break, and hands the advantage straight back.

29.a4 e4?? — Black’s first blunder. The committal push fixes Black’s own e-pawn as a lasting weakness and opens lines for White’s king; 29…f5 instead keeps the pawns intact. After the text White is close to winning — the engine reads about +4.8.

30.Kf1?? — And straight back the other way. 30.f3 was the move: it attacks the e4-pawn at once and opens the f-file for the king, cashing in the weakness Black just handed over. The quiet king step lets the moment pass, and it is level again.

30…Ke5?? — Black returns the favour a third time. Once more the position asked for 30…f5 to shore up the pawns; the king advance ignores it and lets White’s king and pawns take over. Three natural moves in a row, each missing the one structural break the position demanded — a single blind spot, not three separate slips.

31.Ke2 Kd4 — The king strides to d4.

32.b5 cxb5 33.cxb5 axb5 34.axb5 — Four captures empty the queenside and leave White a passed pawn on b5 — outside, and with no neighbour to defend it. It will not promote: in every winning line Black’s king walks over and takes it, and that is what it is for. While Black’s king is away, White’s king goes the other way and takes the kingside pawns. White is winning.

34…Kc5 35.Ke3 f5 36.Kf4 g6 — And here White had one precise win — and a careless near-win that turns out to be only a draw.

37.g4?? — The decisive missed win. The clean path was 37.h4 .

37…fxg4 38.Kxe4 Kxb5 — Now Black is a pawn up, and the position is only equal. 38…Kxb5 recaptures; it is the only move that holds, but an obvious one.

39.Ke5 Kc4 40.Kf6 Kd3 41.Kxg6 Ke2 42.Kh5 Kf3 43.Kh4 Kf4 44.h3 h5 45.hxg4 hxg4 46.Kh5 Kf5 47.Kh4 Kf4 48.Kh5 — The pawns come off, and Black finds the precise hold. The tablebases are blunt: from move 45 it is a proven draw, with nothing left to win.

White reached +9.68 and drew. The win needed one move — 37.h4, holding the h-pawn back as a second threat while b5 kept Black’s king on the wrong side — and 37.g4 traded off exactly the pawns that were doing the work. Against 1979 the half point is a good result on the day. It is also the one that got away.