I'm thinking of 39.Qb5 (threatening both mate and the a pawn forcing an exchange of queens) 39...Qxb5 40.axb5 a4 41.b6 Na6 seems to hold and in fact win for black....

With 39.Bg8 white attacks the immovable (and undefendable h-pawn). Black cannot take the sacrifice as:

At first glance this position looks pretty even. Staring at the board, the only "advantage" that I see for white is the advanced h-pawn. Black's king is more centralized, but that also means that it can't defend his own h-pawn.

I also notice that the black knight currently has no squares it can safely move to, and this sort of bottles up the black queen. Should black try to attack white's h-pawn with ...Qf8, that allows white access to with Qc7+

Black is almost in zugzwang. He can play ...f5 or move his king to his first rank, but I don't see black making any progress. White can play moves such as g4 (to guard f5 again), or relocate his king to the queen's side of the board, then try to exchange queens and invade. Black will be unable to bring his king to the defence of the queen side for fear that white will play Bg8-Bxh7-Bxg7 and get the h-pawn moving.

So, I think my plan is take my time getting the king to the right square (I don't know where that is yet), then exchange queens, the use the bishop's ability to move long distance across the board to win the end game.

Sounds easy, doesn't it?

Well, I can't find a square I like for the white king. Perhaps the first move is to exchange queens. If so

39 Qc8

pretty much forces it. The dual threat of Qxb8 and Qd7+ must be met with

39...Qxc8 40 Bxc8

because the only other move that black could try, 39...Qa7 is met by 40 Qh8!

Now black will try to play 40...Na2, 41...Nc3 and 42...Nxa4 and get his pawn moving. White will have to use his king to stop the a-pawn while using his bishop to go after the h-pawn.

Well, I'm done for tonight. Also, it's unlikely that I will post on Friday or Saturday, as I'm off to Tucson, AZ to visit one of my sisters. Perhaps I can use her computer.

Time to check.

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Material: B for N. White has a spatial advantage and control of the light squares around the Black Ke7, which is cramped and vulnerable to back rank skewers from the White Q. The White Ph6 is so close to queening that Black must not lose Pa7, e.g., to the move Bg8. The endgame advantages suggest that under many circumstances, White can exchange Qs.

Candidates (39.): Bg8

39.Bg8 (threatening 40.Bxh7)

39…Qxg8 [else, White wins Pa7 and has skewer threats even worse than the following.]

40.Qc7+ K moves 41.Qc8+ Kf7 [else, drop Qg8]

42.Qe6+ Kf8 43.Qxd6+ Kf7 44.Qc7+

With the skewer threat on Qg8, White can force the position whether or not Black played 43…Kf7.

44…K moves 45.Qxa5 (threatening 46.Qxb4)

With the pieces off, White can win the resulting K+P endgame, because the a- and d-Ps protect each other against the Black K (although they cannot advance without support of the White K). Thus, 45…Nxd5 is infeasible. Unfortunately, Black has few feasible options rescuing Nb4.

(1) 45…Na2 46.Qd2 completely dominating and winning the N

(2) 45…Nc2 permits White to use the cramped position of the Black K to check until reaching the c-file to fork K and Nc2.

(3) 45…Nd3 46.Qc3

The Nd3 can sacrifice itself for at most a P, after which 47.Qc8+ and exchange of Qs leaves White with a won K+P endgame.