W's first order of business is to put the threat at h2 under control. But how? By bringing the K or the N?

The N, of course, if we're planning to break by c5: B must be obliged to capture with his b-pawn and not the K. So the WK shall come to h2, sacrificing the N in the process. But after c5 and bxc5, who promotes first?

Both promotes on the same move, since from c5 B needs 4 moves to do the job while W needs 4 moves as well, that is: a5-b6-bxa7-a8Q. The fact that B could interpose ...axb6 after b6 is irrelevant here, as he loses the one move that W uses for recapturing: 5-1=4. In the same manner, ...h1Q+ amounts to nothing. At the end, it's the fact that W promotes with check at b8 that decides, since he is the one who plays the first of the 4 requested moves.

In terms of notation of moves, I think we should see something like 55.Kg2! Kxd4 (otherwise the N will capture the eventual B's passed pawn when this latter comes to c3) 56.c5 bxc5 57.a5 c4 58.b6 c3 (58...axb6 59.a6! (not 59.axb6? c3 60.b7 c2 61.b8Q c1Q is draw: promoting at the same without check is not enough for a win) 59...c3 60.a7 c2 61.a8Q+; 58...a6 lets W promote first: 59.b7 c3 60.b8Q c2 61.Qc8) 59.bxa7 c2 (59...h1Q+ 60.Kxh1 c2 61.a8Q+) 60.a8Q+ K-safe 61.Qc8.

A nice one. Time to check if my delirium is just imaginary. XD

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Hm. Interesting. I don't think this puts my analysis out of business, since the fact that W has the opposition is unimportant here. Let's suppose that W is on move here after 60.Kf4 and so, B has the opposition:

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The BK is restrained in its mobility: it must watch for the c7 push. Furthermore at some point B is likely to lose the opposition since the d7-square is out of reach. So 61.Kf5! Kc7 (61...Kd5 62.c7; 61...Ke7 62.Ke5) 62.Ke5 Kc8 (62...Kd8 63.Kd6) 63.Ke6 Kd8 (63...Kb8 64.Kd7) 64.Kd6 Kc8 65.c7 Kb7 66.Kd7 Ka8 67.c8Q+ is mate.

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I'm wondering whether the time will come when, instead of always questionning why a certain GM played this or that, we will start promoting time controls that allow players time for thinking about what they play during endgames... :)

<tacticalmonster> <In the game continuation, I found a pretty interesting variation. One way to continue:

55 Kxe4 56 c5 Kd5 57 c6 Kd6 58 Kxh2 a6! (trading pawns in defensive position is good technique)

59 Kg3 axb5 60 axb5 Kc7 61 Kf4 Kd6 62 Kf5 Kc7 63 Ke6 Kc8 64 c7! (the key move! any other move draws)

64…Kxc7 65 Ke7 Kc8 66 Kd6 Kb7 67 Kd7 Kb8 68 Kc6 Ka7 69 Kc7 Ka8 70 Kxb6 with basic winning king and pawn ending>

This is just a small point of order for the record, but the line posted by <tacticalmonster> you reference in your post needs some clarification. After move 63 by black, here is the position.

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At this point, any move by white wins in this position (not c7 only). However, c7 , sacrificing the pawn, does need to be played at some point for black to win. Below is the position after 70 Kxb6 in his diagram which proves his point.

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Yes, we are in total agreement.

You figured out the correct line if pawns are traded and <OBIT> summarized the overall position at move 56 nicely.

Thank you for pointing out! It is probable that different people may have a different opinion about what is obvious and what is not. To me, it was evident that the protected passed c-pawn was a winner, no matter B's play. It was a "no-need-to-give-oneself-a-headache-piece-of-play- . You see it and you know it wins. But for others I agree it could not be the case.

On the other hand, the real challenge to was to determine whether W could have a successful breakthrough, that is, one that promotes with check whatever Black plays. And for someone else, this could just be his/her piece of cake. :o)