# Sharp pawn endgame - can it be calculated to the end? With Computer engine?

White to move, here is a brief summary of my analysis where I attempted to determine exact evaluation. Number of pawns is equal but White's 2 pawns on the queenside are held by one Black's pawn, so in a sense Black has an extra pawn on the rest of the board.
`1. a4` with pawn breaks on both sides of the board by both White and Black (!) leads to a difficult queen endgame for White.
`1. Kc3` (played by me in the game) is a blunder that should lose after 1...f4! since then Black puts pawns on e4 and f4 and goes to the kingside with his king to pickup White's pawns.
`1. Kd3` is possibly best as now `1...f4` is met with `2.Ke4`. But Black instead plays `1...Kf7` and manoeuvres, waiting for zugzwang. Can Black win? Can a computer engine be used in this day and age to determine exactly if this position is a draw or win for Black?

This is a pawn endgame - which are supposed to be evaluated precisely... I feel this is likely a draw, but can't prove exactly. Is there Mr. Grigoriev in the audience?

``````8/7p/4k3/1p2ppP1/1P5P/8/P1K5/8 w - - 0 38
``````
• This endgame can be calculated to the end with an engine if tablebases are provided as well. White can force a draw in this position. If you are interested I could post an answer. Best regards. Commented Mar 1, 2014 at 20:15

It's clear that Black has the following advantages:

1) His king is better centralized.

2) He has two connected passed pawns.

3) White has no passed pawns because one Black pawn holds up two White ones on both the queen and king sides.

White's main advantage is that he has two rook pawns, which could lead to "outside" passed pawns. Even so, it might take the sacrifice of a pawn for White to get a passed pawn.

So I would give Black the advantage overall, and say that he should win with proper play. White should draw with great difficulty if at all.

I'm basing this judgment on "pattern recognition," because I am a only a 1500 player.

• White can potentially create two passed pawns - if he plays h5 and g6, or if he plays a4. In most lines - only one pawn needs to queen.
– Joe
Commented Nov 3, 2012 at 23:03

This is actually a drawn position with correct play. As expected, the two sides with pawns are actually more important in the end-game than the center pawns (because the center pawns can be effectively barricaded.) Here is a full analysis done GNU chess (your move kd3 is correct, however, the difficult moves come later on in the game when there are two queens on the board.)

GNU Chess comes up with this:

``````[fen "8/7p/4k3/1p2ppP1/1P5P/8/P1K5/8 w - - 0 38"]

1. Kd3 f4 2. h5 f3 3. Ke3 e4 4. g6 hxg6 5. h6 Kf7 6. a4 bxa4 7. b5 a3 8. b6 a2 9. b7 a1=Q 10. b8=Q Qe1+ 11. Kf4 Qh4+ 12. Ke3 g5 13. h7 Qxh7 14. Qb7+ Kg8 15. Qc8+ Kf7 16. Qd7+ Kg6 17. Qe6+ Kh5 18. Qh3+ Kg6 19. Qe6+ Kh5 20. Qh3+ Kg6 21. Qe6+ 1/2-1/2
``````
• awesome, is there a way to get this as pgn? Another question is - did you just plug it into this engine and that's what it came up with? How much time per move was it given? The big dilemma I have is how much to trust engines and which ones ...
– Joe
Commented Nov 11, 2012 at 16:22
• @Joe: This is GNU chess, and although it has never been given an official rating, according to the FAQ gnu.org/software/chess/chess_faq.html#B.2 it was rated ~2200 over 10 years ago. On the advent of modern PCs, it has a much higher rating. I've seen it playing on FICs games with a rating over 2800. The time thinking per move is actually not a parameter in GNU chess, but the depth of search was set to the default (which is 20 I think.) It has horizon expansion I think so that is a soft limit.
– ldog
Commented Nov 13, 2012 at 7:07
• @ldog: I agree that this position looks like a draw after 1 Kd3 e4+. But the line given by GNU Chess looks suicidal for White! Instead of 2...f3, why doesn't 2...Kf5 win quickly? If 3 g6 hxg6 4 h6 Kf6 wins. Commented Sep 16, 2013 at 23:35

Black needs four moves to promote the black f-pawn, if white doesn't stop it with his king. White needs also four moves to promote. I.e.,

``````[Variant "From Position"]
[FEN "8/7p/4k3/1p2ppP1/1P5P/8/P1K5/8 w - - 0 1"]

1. h5 f4 2. g6 hxg6 3. h6 f3 4. h7 f2 5. h8=Q
``````

But, black stands in its square and in reality this would happen:

``````[Variant "From Position"]
[FEN "8/7p/4k3/1p2ppP1/1P5P/8/P1K5/8 w - - 0 1"]

1. h5 f4 2. g6 hxg6 3. h6 Kf7 4. Kd3 Kg8 5. Ke4 Kh7 6. Kf3 Kxh6
``````

where black simply picks up white's free pawn and then goes on to assist his three connected free pawns.

Fortunately, white also has a pawn majority on the Queen's side, which also costs four moves to promote:

``````[Variant "From Position"]
[FEN "8/7p/4k3/1p2ppP1/1P5P/8/P1K5/8 w - - 0 1"]

1. a4 bxa4 2. b5 f4 3. b6 f3 4. b7 f2 5. b8=Q
``````

But black also stands in that square. Black can not stop both, the b-pawn and the h-pawn however:

``````[Variant "From Position"]
[FEN "8/7p/4k3/1p2ppP1/1P5P/8/P1K5/8 w - - 0 1"]

1. a4 bxa4 2. b5 f4 3. b6 Kd6 4. h5 f3 5. g6 hxg6 6. hxg6 f2 7. g7 f1=Q 8. g8=Q
``````

That is the best computer line and now it is a draw due to infinite check.

Note that black must play 1... bxa4 or white simply promotes the a-pawn, stopping blacks pawns with his king: also black needs the threat of two pawns promoting.

On top of that, white must play 2... hxg6 and not h6 as before. For example (the best computer line):

``````[Variant "From Position"]
[FEN "8/7p/4k3/1p2ppP1/1P5P/8/P1K5/8 w - - 0 1"]

1. a4 bxa4 2. b5 f4 3. b6 Kd6 4. h5 f3 5. g6 hxg6 6. h6 f2 7. h7 f1=Q 8. h8=Q Qf2+ 9. Kd1 Qd4+ 10. Ke1 Kc6 11. Qb8 Qxb6 12. Qe8+ Kd5 13. Ke2 Qc6 14. Qd8+ Kc5 15. Kf2 Kc4 16. Qd1 Qc5+ 17. Ke2 a3 18. Kf1 e4 19. Qc1+ Kb5 20. Qa1 Qc4+ 21. Kg1 a2 22. Kh1 e3 23. Kg2 Ka4 24. Qd1+ Ka3 25. Qd6+ Kb2 26. Qb8+ Kc2 27. Qa8 e2 28. Qa5 Qe4+ 29. Kf2 e1=Q+ 30. Qxe1 Qxe1+ 31. Kxe1 a1=Q+ 32. Kf2 Kd3 33. Kg3 Qd4 34. Kh3 Qg1 35. Kh4 Ke3 36. Kh3 Kf3 37. Kh4 Qg3#
``````

where white avoided queen trade as long as possible (pointlessly). The actual problem being that if white would win one pawn, then black would be able to immediately trade queens and easily win with king plus two pawns against king. For example:

``````[Variant "From Position"]
[FEN "8/7p/4k3/1p2ppP1/1P5P/8/P1K5/8 w - - 0 1"]

1. a4 bxa4 2. b5 f4 3. b6 Kd6 4. h5 f3 5. g6 hxg6 6. h6 f2 7. h7 f1=Q 8. h8=Q Qf2+ 9. Kc1 Qc5+ 10. Kd1 Kc6 11. Qa8+ Kxb6 12. Qxa4 Qd4+ 13. Qxd4+ exd4 14. Ke2 Kc5
``````

or any of the other billion possibilities. It is however crucial to understand what K+Q+3 pawns against K+Q has infinitely larger chance to win in this manner than K+Q+2 pawns against K+Q.

Also keeping it a draw with infinite check is an art by itself that isn't very trivial. In general you just want to keep the queen on the board and keep giving check. Try to play this against a computer to see all the pitfalls.