Mamedyarov – Nakamura, Tromsø ending

Towards the tail end of round 11 (the final round) of the Tromsø Olympiad, whilst I was watching to see if David Howell could win his struggle, I also watched several other endings. The one which caught my eye most was Mamedyarov-Nakamura, where I was intrigued to see if it was a win for white or a draw: I didn't know which.

The crucial position

Hikaru took on g5, 40…hg, and resigned a couple of moves later. The point is that white will eventually sacrifice on f7 and the resultant king and pawn ending is won: white's king muscles black's king away from g6, and the pawn promotes.

The spoiler

On the evening of the game Hikaru tweeted:

I was puzzled. If 40…hg was the losing blunder, then what should he have played? The only sensible alternative is (perhaps, but we will come to that later) 40…h5.

Before I could look at it, Mihail Marin wrapped his excellent coverage of Tromsø (to be honest, Chessbase were superlative in their coverage) with his round 11 commentary which included this game:

Mihail says that it is all over after 38 h4: so who is right?

40…h5

I have therefore had a look at the ending, and 40…h5 also loses. It is understandable: the sac on f7 and then pushing away of the king from defending g6 doesn't depend on whether or not there are h pawns on the board. Stockfish helpfully points out that after 41 Rf7+, take things off, it is mate in 22.

Once I understood this, I re-read Mihail's comments, and understood the wisdom of his earlier comment about the move h7-h6 being an important mistake.

So is Mihail correct? Of course, Hikaru's comment was a post game tweet.

40…passing

So what happens if black passes with say 40…Rf1?

White has two options: either to take on h6 (41 gh+ Kh6 42 Bf7 (42 Rf7?? Rf7 43 Bf7 Kh5=, or even 43…g5=, since h8 is a black square) and try to win the RBvR ending (in which case Hikaru is correct, since that ending is technically drawn- unless the resultant positon is one of those where black is lost) or try to manoeuvre into a positon where the sacrifice can be made on f7. However, he has better.

So, 41 Bc4 Rf2 42 Ke3! Rf5 43 Bd3! (pushing the rook off the f file) Rc5 (I don't think it matters whether it goes to e5, c5 or a5: a key point is that the Bd3 controls f1) 44 Kd4 Rc8 45 Bc4 Rf8

I think this position is won, by zugzwang. I even think the pretty line 46 Be6! wins, since if 46…Kg8 then 47 Rf7 Rf7 48 Ke5! sets up the position correctly so that black doesn't have the opposition, and white can muscle into g6.

Conclusions

Mihail is correct, and Hikaru couldn't have saved the game at move 40. If his game could have been saved it was earlier, by not moving his h7 pawn, for by doing so he weakens the Pg6. Interesting, and instructive.

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