Move 38 discussion: Everyone vs stockfish

[MooMoo2]

The poll for moves 36/37 just closed. The most popular move was Rb8+, and if 36...Kh7, then 37. Rb7+. Stockfish did respond with 36...Kh7, and the response to 37. Rb7+ was Kg8.
The FEN is:
6k1/1R6/5p2/4nN1p/8/6P1/r1r4P/5RK1 w - - 4 38

Game so far: 1.e4 e6 2. d4 d5 3. Nd2 c5 4. Ngf3 Nf6 5. exd5 exd5 6. Bb5+ Bd7 7. Bxd7+ Nbxd7 8. O-O Be7 9. dxc5 Nxc5 10. Nb3 Nce4 11. Nfd4 O-O 12. Nf5 Re8 13. Nxe7+ Rxe7 14. f3 Nd6 15. Bg5 Nc4 16. Bxf6 gxf6 17. Qd4 Qb6 18. Qxb6 axb6 19. Rfd1 Re5 20. f4 Re2 21. Nd4 Re4 22. Nf5 Nxb2 23. Rxd5 Rxf4 24. g3 Rc4 25. Nh6+ Kg7 26. Nf5+ Kf8 27. Rd7 Rxc2 28. Nh6 Kg7 29. Nf5+ Kg6 30. Nh4+ Kg7 31. Nf5+ Kh8 32. Rxf7 Nd3 33. Rxb7 Ne5 34. Rf1 h5 35. Rxb6 Raxa2 36. Rb8+ Kh7 37. Rb7+ Kg8

[Brian-E]

As people wrote before, we have 38.Nh4 which defends against the mating threat and prepares to swap our h pawn for the black f pawn which would seem to be a dead draw.

But we could perhaps even better carry on checking with the rook for the moment to force Black to put it on a worse square (not defending its f pawn and vulnerable to checking from our other rook) if it still wants to avoid repetition of position. For example 38.Rb8+ Kf7 39.Rb7+ Ke8 and only now 40.Nh4.

[WMHalsdorf]

Originally Posted by Brian-E

As people wrote before, we have 38.Nh4 which defends against the mating threat and prepares to swap our h pawn for the black f pawn which would seem to be a dead draw.

But we could perhaps even better carry on checking with the rook for the moment to force Black to put it on a worse square (not defending its f pawn and vulnerable to checking from our other rook) if it still wants to avoid repetition of position. For example 38.Rb8+ Kf7 39.Rb7+ Ke8 and only now 40.Nh4.

Throw in another check and it makes it even better for us to draw.

[science_man_88]

if only I could see
38. Nh6+ Kh8
39. Rxf6 Rc8
40. Nf7+ Nxf7
41. Rxf7 ...

continuing well for us and working like it should.

[WMHalsdorf]

Originally Posted by science_man_88

if only I could see
38. Nh6+ Kh8
39. Rxf6 Rc8
40. Nf7+ Nxf7
41. Rxf7 ...

continuing well for us and working like it should.

39... Rc!+
40.Rc1 Nf3+
41.Kh! Rxh2#

[gd_barnes]

I definitely don't think we want to play more checks at this point. We need to go with 38. Nh4. Forcing black's king towards the center with 38. Rb8+ puts his king in better position and takes even longer to force home the draw. He is likely not going to allow a draw by repetition (or accept a draw offer) if he believes he is improving his position. In other words, he still has "game" to continue playing on.

Reasons:
1. By having his king in the center on the e-file instead of the g-file, he more easily and quickly can reach the middle of the board in a late end game situation.
2. We lose mate threats in some variations -and/or- repetition threats that are possible by having black trapped on his king-side and back rank or two. This is due to us having our 1st-rank rook on the open f-file after moving our knight to h4 in several cases. Black cannot easily escape the king-side corner.
3. We can save additional multiple checks on black's king for a little later when it becomes clearer that we may be able to force a repetition on the king-side.
4. Due to #2, black can pick off our h-pawn and we have great difficulty gaining it back in many variations.

Example:
38. Rb8+ Kf7
39. Rb7+ Ke8 (not 39...Ke6? 40. Nd4+)
(I think the point is clear now that we don't want to play any more checks with 40. Rb8+ so...)
40. Nh4 Ng4

We are in a tough spot, i.e.
41. Re1+ Kd8
-or-
41. h3 Nf2
-or-
41. Rb1 Rxh2 (or Nxh2)

In all attempts, we eventually drop a pawn because we no longer have the nice tempo-gaining mate threat of 41. Rd1 and it is quite difficult for us to get it back. Black is also free to have his king wonder around and avoid us. With black's king on g8, 40. Rd1 is a mate threat, which is very annoying to black's position. With his king now on e8, the threat is lost.

So...why try for a draw a pawn down (even temporarily) when we can more easily play for the draw without dropping the pawn?

Here are the best lines that I see:
(1)
38. Nh4 Rxh2
39. Rxf6 Rc2 (or Rd2 or Re2) [freeing up both of his rooks]

Great position for us here. It's so good that analysis is not really even required to see it. With black's king trapped in the corner and so wide open, we have many good moves, i.e.
40. Rb3 protecting our pawn.
40. Rb5 giving black great difficulty in protecting his pieces.
40. Rf1 by covering up our king, we are threatening an easy draw by repetition.

There are other decent moves by us but this should be enough to demonstrate that 38. Nh4 Rxh2 is good for us.

(2)
38. Nh4 Ng4
39. Rd1 Ra8 (or Rc8)
40. Nf3
(We've backed black off and he cannot easily make progress.)

(3)
38. Nh4 Ng4
39. Rd1 Rd2
40. Rxd2 Rxd2
41. Nf3
(Where now?)

The bottom line is: 38. Rb8+ is not exact. It's likely not a fatal mistake but one that could prove fatal if we fail to play exactly. Don't force black into a better position with meaningless checks "hoping" that he goes into repetition mode. Keep him trapped in his king-side corner where we have many potential repetition and mate threats on future moves. He has shown that he will not easily accept draws or be forced into repeating moves so we should play accordingly and ultimately force his hand.

[Brian-E]

While disagreeing with your reason #1 above Gary (in all endgames both kings will be required on the kingside where all the pawns are, so the centre and queenside are then irrelevant, which was my main reason for first forcing the Black king into the centre), I accept the other arguments you write and see now from your demonstrated lines that our extra mating threats based on Rd1 are useful for keeping material equality. And indeed, we should not go a pawn down unnecessarily, drawn though all endgames would still be.

So I agree with 38.Nh4 thanks to your posting.

[WMHalsdorf]

While Nh4 is needed at some point I was 100% sure it was doable at this point until now.
So Nh4 works for me.

[Brian-E]

Originally Posted by science_man_88

if only I could see
38. Nh6+ Kh8
39. Rxf6 Rc8
40. Nf7+ Nxf7
41. Rxf7 ...

continuing well for us and working like it should.

You went ahead and voted for 38.Nh6+ Science Man, I notice.

Possibly WMH's response to your post wasn't clear because it contains a couple of notation errors, but could anyone who hasn't already realised this please note that 38.Nh6+ is a horrible mistake? (Just in case anyone else feels like voting for it: it would be a disaster if we ended up playing it.) Black is threatening the simple mate-in-three starting ...Rg2+ and our knight is needed to defend against that threat. The refutation to Science Man's line, as given by WMHalsdorf, is (38.Nh6+ Kh8 39.Rxf6) 39...Rc1+ 40.Rf1 Nf3+ 41.Kh1 Rxh2 mate.

[LaurV]

Originally Posted by Brian-E

but could anyone who hasn't already realised this please note that 38.Nh6+ is a horrible mistake? (Just in case anyone else feels like voting for it: it would be a disaster if we ended up playing it.)

I agree with you that is not the best move, but the game is still playable, it is not the end of the world if you play it. Of course the other moves in the list are much better. I "accidentally" had a look to that move yesterday night, after I saw it in the list, and that was after reading WMH's post. I was intrigued why the move is still in the list, when it was clear it is bad for white, eventually ending with a mate. So I had a deeper look to it (and no, I did not use SF this time). The game will still be playable, and will still result in a draw, but we may play with a horse less, and getting the draw would be more difficult. But is not an easy black win. Anyhow, I would not vote for it, in a thousand years.

Details: if 38 Nh6+, black must Kh8, otherwise, if Kf8 we can bring the second rook into the fray, and having a clear draw with 39. Rxf6+ Ke8 40 Re6+ Kd8 41. Nf7+ Nxf7 42. Rxf7 Rg2 43. Kf1 Rxh2 44. Kg1 Rhg2+ 45 Kf1 Rgd2 Rfe7 and we have eternal check.

So, 38 Nh6+, Kh8, and the only move we can play now to avoid the mate is 39 Nf7+, Nxf7, and we can't take the black horse due to mate threat (as described by WMH before), therefore 40. Rxf6 Rc1 (or a1, he can't take the pawn in h2 because loses the horse), 41. Rf1 and from here, god knows... maybe Rxf1+ 42. Kxf1 Kg7 43 h3, and we play a pawn against a horse. It is not a clear black win, but neither an easy "white" draw...

I would not vote for 38 Nh6+, for sure.

[Dubslow]

Originally Posted by LaurV

I would not vote for 38 Nh6+, for sure.

Then why did you