Thinking = Results
So, I hope that you did what Dvoretsky & Petr encouraged us to do – THINK!
The first thing you should notice is that if it’s black to move, Bxc2 is a simple win. Therefore it must be white to move otherwise there’s no point!
The second thing to notice is that black actually has two threats; Bxc2 and Ba2 then to c4, when again it’s a simple win for black.
Therefore white’s first move becomes obvious – there’s only one candidate!
If black takes white can draw by 2. Kd2 and then to c1 and b2 chasing the bishop (or even to c3)
This then gives us black’s response. Again only one candidate since the pawn must stay on the board.
1. … b4
And now white must defend the pawn c2. 2. Kd3 is just bad as the pawn is pinned; 2. … b3! 0-1
So that leaves either 2. Kd2 or 2. Kd1. Is there a difference? (Well, of course there is, or what’s the point! But WHAT is the difference?)
This is a tricky question. The key idea to understand is that when the bishop goes to a2, white must be able to play c3, when if bxc3 either Kxc3 or Kc2 will round up black’s last pawn and if instead of bxc3 black tries b3 white can draw by Kb2-a1-b2 as the capture of the pawn c3 will result in stalemate.
2. Kd1! Kc5 3. Kd2! The point! It must be black to move in this position. If 3. … Ba2 then 4. c3 b3 5. Kc1-b2-a1 draw. So…
3. … Kxc4 (stopping 4. c3) 4. Kc1 Ba2 5. Kb2 and the bishop is trapped!
BUT THAT’S NOT THE END OF THE STORY!
Can you see black’s continuation?
5. … Bb3!!
And black wins.
So is that the solution? The position is a win for black after all?
In fact 5. Kb2 was an error. After 6. Kd2!! the final truth is revealed – DRAW.
6. … Bb1 is a repetition, while any king move by black allows c3.
When I first saw the starting position I never imagined how intricate the solution would be.