Textbook Ending

 In today's Morning Membership tournament on Chess.com, two players found themselves in a difficult pawn ending with under a minute remaining. The time control was game in five minutes with a two second increment (5+2). White had 18.5 seconds and Black had 38 when Chris started showing the game on Twitch. Chris Bird is the tournament director and streams these weekly events.

Both players shuffled their kings back and forth until a repetition occurred. When players are premoving, as they seemed to be doing, draw offers are often refused even as they are made. It was not clear from Chris's discussion whether he knew that White had a winning position.

In the screenshot, White has just played 51.Kd4.

There was an alternative.

51.Kb5 wins.

After 51.Kb5!

This move can be frightening with less than twenty seconds left, but it is the correct move. White has stepped out of the square of Black's pawn. If White fails to promote first, or set up a checkmate, Black will also promote.

After 51...Kc8, White has two ways to proceed.

52. Kc6, or 52.a6. I played the latter against Stockfish 11, which replied 52...e3.

White to move

Now, only one move wins for White. All others lose.

After 53.b6+, 53...Kc7! leaves White lost. However, 53...Kb8 allows 54.Kb6 and 55.a7#. In one of the textbook lines beginning with 51...Kb8, Black promotes the pawn just before getting checkmated.

53.a6 allows 53...Kb7 and White can make no further progress, while Black's e-pawn cannot be stopped.

53.Kc6! e2 54.b7+

Black to move

54...Kb8 55.Kb6 e1Q Black promotes first, but White checkmates with pawns. Stockfish chose a longer checkmate.

54...Kd8 55.b8Q+ Ke7 56.Qe5+ and White wins.

While watching the Twitch stream, I saw a familiar pattern. After the tournament, I out that my belief that White was winning was indeed correct. Although as a practical matter, with less that twenty seconds remaining, I, too, might have taken the draw.

The textbook position appears in Dvoretsky's Endgame Manual. Consequently, it is a position that I have played out several times with my students (see "Pawn Ending Flash Cards").

White to move

I know the technique through training with positions from Dvoretsky. Likely other books have the position as well, and it appears in Harold van der Heiden's Endgame Study Database. Heiden credits Reuben Fine, Basic Chess Endings (1941), while Dvoretsky credits the nineteenth century composers J. Kling and B. Horwitz.*

In any case, the first critical position is reached after the moves:

1.Kd4 Kg4 2.h4 Kh5 3.Ke3 Kg4 4.Ke4 Kh5 5.Kf4 Kg6 6.g4 Kg7

White to move

7.g5 is a mistake. White can move the king, but the way forward is 7.h5!

7...Kh6 8.Kf3

Heiden has 8.Ke4 here. Dvoretsky's solution is three moves longer, so seems to offer better defense by Black. Both 8.Kf3 and 8.Ke4 have the same number of moves to mate, according to my chess engine.

Dvoretsky points out the importance of triangulation for White.

8...Kg5 9.Ke4 Kh6 10.Kf4 Kh7 11.g5 Kg7 12.g6 (12.h6 loses) 12...Kf6 13.Ke4 Kg7 14.Kf3 Kf6 15.Kf4 Kg7

White to move

Now, White's confidence comes into play, as it is time to leave the square of Black's passed pawn.

16.Kg5 c3 17.h6+ Kg8 18.Kf6 (see the critical Kc6 in my analysis of what might have been above).

18...c2 (so close to becoming a queen!)

19.h7+ Kh8 

White to move

20.Kf7 c1Q

Black promotes, but White will promote with check.

21.g7+ Kxh7 22.g8Q+ Kh6 23.Qg6# 

This ending is worthy of study. Perhaps if your nerves are calm, you can win with a quarter minute and a two second increment should you find yourself is a comparable position.


*Fine, on my reading presents a similar position that is a draw. He does mention winning chances, though, if the pawns on the left are another row to the right of the position illustrated here. There seems some room for some historical research.