09 February 2017

A Technical Win?

The annotations in Chess Informant 44/672 by Oscar Panno indicate that Black is in zugzwang. The game was Panno -- Leskovar, Buenos Aires 1987.

Black to move
After 57.Rc1
Even so, it is hard to see how White made significant progress over the next 22 moves. I get that the bishop is forced to move, which allows White to maneuver his king to h4. That would make it possible to exchange rook for bishop should the minor piece again come to rest on g4, but White cannot force it there.

57...Be6 58.Kf3 Bd5+ 59.Kf4 Be6 60.Rc3 Bg4 61.Kg5 Kg2 62.Kh4

Black to move


Panno asserts that this move is an error, but it is not easy to see why. He offers two moves that are equal.

62...Kg1! 63.Rc4 Bf3 64.Kh3 Bg2+=


In the second case, it is easy to see that exchanging rook for bishop draws. In the first case, White cannot make progress. As the course of the game from this point reveals, White's plan was to evict the Black king from the corner so that his own king can move there.

Six-piece tablebases reveal that Black has four moves that draw from the diagram and that 62...Kf2 loses in 66 moves. Panno's annotations were written before these tablebases existed. Panno's annotations also do more to help the student gain an appreciation of the ideas in this ending.

Panno's line after 62...Kh1 resembles positions found in books that point out the handful of exceptions when rook versus bishop is not drawn in a pawnless ending. 63.Rc4 Bf3 64.g4!! White wins a pawn or quickly checkmates Black.

63.Rc4 Bf3 64.Kh3± Bg2+ 65.Kh2 Bf3 66.Rf4

Black to move

66...Ke2 67.Kg1

The six-piece tablebases indicate that this move is best, but my engines prefer 67.Kh3. Stockfish cannot access the tablebases. Hiarcs can, but I only have up to the five-piece on my computer. My external hard drive has sufficient space for the six-piece, but I have not downloaded them. I am not even certain they are available for download anywhere.

67...Ke3 68.Ra4 Ke2 69.Ra2+ Ke3 70.Kf1 Bg4 71.Ra3+ Ke4 72.Kf2

So, the point was not to occupy the corner, but rather to chase the Black king from his fortress.

72...Kd4 73.Re3

Black to move


Black's king is cut off from the kingside, but Black's bishop makes the advance of White's king difficult.

74.Re8 Bg4 75.Ke1 Kd3 76.Re7 Bh3 77.Ra7 

The advance of White's king is necessary, not keeping the Black king away from the queenside.

Black to move


Hiarcs prefers 77...Bg4 78.Kf2 Ke4 79.Ra4 Kd3 80.Rb4 Bd1 81.Rf4 Be2 82.Rf5 Bg4 83.Rb5 Kd4 84.Rb4+ Kd3 85.Ra4 Bd1 86.Ra7 and to my eyes, White is making no progress.

The tablebases may claim this as a win, but if White does not win the pawn by move 104, the game will be drawn by the fifty move rule (see "Max Judd's Draw Claim").

However, after 77...Bg2, Hiarcs declares that White has a forced checkmate in 37 moves.

78.Kf2 Bh3 79.Ra3+ Ke4 80.Ra4 1-0

It appears that Leskovar lost on time.

The game might have continued: 80... Kf5 81.Ra5+ Kg4 82.Rc5!+- (Panno's annotations).

Black to move

Black must move either bishop or pawn, losing whichever one moves. Moving the pawn leads to 83.Rc4+ and 84.Rxh4. I could win the resulting position in a time scramble against a computer. Moving the bishop leads to an elementary checkmate.

Perhaps by studying Panno's annotations to this game, I might have absorbed some ideas about how the weaker side might construct a fortress, or how the stronger might play for an advantage. In practical play, I suspect this ending would usually end as a draw despite the assurance tablebases give us that it is a technical win.


  1. KRP versus KB can actually be very hard against best defense, especially if it is a rook pawn.

    From your final position, allow black to lose the pawn in a reasonable way, say ...h4 Rxc4+ Kg5 Rxh4, then actually try blitzing it out against the computer.

    Two RP vs B positions that are hard:


    1. Maybe I was a bit over-confident based on winning lots of these in blitz games. I usually manage to swap rook for bishop and convert to a winning pawn ending that I can almost play via premove. Of course, with a rook pawn there are more draws.