There's actually not much to choose between the two moves. After 42. fxg6 Be6+ white has to give up his queen pretty quickly to delay the mate.

But black also mates with 42...Bxe4

click for larger view

Black is threatening both Bf5+ and Rd3+. White will need to give up loads of material to delay mate.

After 42. fxg6, Fritzie prefers 42. Be6+ because he says it is mate in 11. But his second choice is 42. Bxe4 which is mate in 16, and that's not too shabby. I went for Be6+ as it seemed the cleaner kill, although I think either move is fine as a solution.

Nor me - I was surprised when folk started mentioning it.

I guess it all depends on what you saw when you first looked at the puzzle position:

click for larger view

Some folks will look at this and focus on the vulnerable and stalemated white king on h3. And these folks (which I think includes both you and me) will play Be6+ at the first opportunity. Always look to check a stalemated king, right?

But others will look at this position and see instead the inadequately protected white bishop on e4. The only thing which is saving this bishop is white's threat of Qxg7#. As soon as the Qxg7# threat is removed, these folks will think first of Bxe4 or Qxe4.

I think 41...g5, with the idea of 42...Qh4+ mate, is the solution. I don't see anything better for W than 42.fxg6 e.p. Bxe4 43.g7+ Kg8, when B wins the WB. An important point is that the heavy W pieces don't have access to either f8, g8 or h8.

Time to check.

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White's path to destruction.
=(0.00):16.f3. Better, Nxe4, +0.46.
(-0.60):18.e3. Better, Bxf4, =0.00.
(-0.94):24.d5. Better, fxe6,-0.74.
(-2.17):34.Qf3.Better, Rc6, -0.75.

Black stumbled: the third best move,
(-0.89):37...Rxd5. Better, g5, -3.64, or Bxd5, -2.53.

The solution is: 41...g5! Black threatens a mate on h4. And if 42.PxP/g6 en passant (?); then 42...Be6+; is the quietus. ( I have always wanted to use that word - but in its proper context.)

***** ***** ***** ***** ***** ***** ***** *****

<<<Sep-08-10> wals:>

<<<<<<<<g5 was the killer move> and I didn't get it,> damn, blast and bugger.> White's path to destruction.>
=(0.00):16.f3. Better, Nxe4, +0.46.>
(-0.60):18.e3. Better, Bxf4, =0.00.>
(-0.94):24.d5. Better, fxe6,-0.74.>
(-2.17):34.Qf3.Better, Rc6, -0.75.>

<<Black stumbled: the third best move,> (-0.89):37...Rxd5. Better, g5, -3.64, or Bxd5, -2.53.>>

<<<White not to be outdone, responded:-> (-5.42):38.Rxd5. Better, Bxd5, -0.92.>
(-11.53):39.Rg1. The best move was Bxd5, -5.42.>

<So White was really scratching and no doubt an unhappy chappie.>>

Black is two pawns up but white is threatening immediate mate on g7.

First I wanted to try 41....Qh4+. 42. Kxh4 (only legal move) g4+. But it doesn't work.

41....Qxf5+ 42- Bxf5 Bxg2+ 43. Rxb2 also fails.

Also 41.... Qe3+ does not work.

After 41.....Qg5 white continues 42. Qxg5 hxg5 43- Bxd4 Rxd4 44. Rxg5 and although black is a pawn up the game is far from won.

But now I think I see it.

41....g5 ! Now black is threatening mate, with Qh4. The only reasonable way to stop it is with Qg3, Qg4 or Qc2. But after exchange of queens, all these result in the loss of the bishop on e4.

Sometimes I see the correct move straight away, but today I went up all the wrong avenues before seeing the right path.