18

This is the position with White to move. This was created by Lazar in 1935 according to Susan Polgar in a Chess Daily News article from 5/27/2008.

[FEN "8/3P4/3b4/8/8/1p2k2p/1Pp4P/2K5 w - - 0 1"]

Can White draw this?

The obvious starting move is promotion of the d pawn. Promoting to a knight or a bishop loses to Bxh2.

Promoting to a Queen leads to Bf4. Checkmate can only be avoided by Qd2+. But Kf3 and Qxf4 should also lose as Black is in time to take the h pawn and that probably wins.

Promoting to a Rook is probably the only choice but I don't understand how the position will be drawn.

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26

The first half of white's move is forced - d8. Then white has a choice of knight, bishop, rook or queen. Black has two threats which white must parry to get a draw. The first is to play Bf4 and then move the king out of the way to deliver checkmate. The second is to take the white h pawn and then queen the black h pawn.

Let's look at what happens if white chooses a queen.

[fen "8/3P4/3b4/8/8/1p2k2p/1Pp4P/2K5 w - - 0 1"]

1. d8=Q Bf4 {threatening mate} 2. Qd2 Kf3+ 3. Qxf4 Kxf4 4.Kd2 Kf3 5. Kc1 {the white king has to stop the c pawn queening} Kg2 6. Kd2 Kxh2 {and the h pawn is going to queen}

Can white draw by choosing a knight?

[fen "8/3P4/3b4/8/8/1p2k2p/1Pp4P/2K5 w - - 0 1"]

1. d8=N Bf4 {threatening mate} 2. Ne6 Bxh2 {now going to threaten to queen the h pawn} 3. Ng5 Ke2 {threatening mate again} 4. Nxh3 {taking the deadly h pawn and stopping the mate!} Ke1 {putting white into zugzwang} 5. Ng1 Bf4#

The problem was the knight couldn't lose a move whereas the bishop could. How about if white chooses a bishop?

[fen "8/3P4/3b4/8/8/1p2k2p/1Pp4P/2K5 w - - 0 1"]

1. d8=B Bxh2 2. Bb6+ Ke2 3. Bc7 {inviting stalemate by BxB} Bg1 4. Bb6 {asking for stalemate again} h2 5. Bf2 h1=Q 6. Bg3 Be3#

That just leaves the rook. The advantage the rook has over the queen and bishop is that it can parry Bf4 mate threats by Rd2. Then when the king moves out of the way white is stalemated because the rook can't take the bishop. Furthermore if white can play Rd3 then that threatens the black b3 pawn which frees the white king to take on c2. Let's see how that could go.

[fen "8/3P4/3b4/8/8/1p2k2p/1Pp4P/2K5 w - - 0 1"]

1. d8=R Bf4 {threatening mate} 2. Rd2 {blocking the threat} Be5 (2...Kf3= {stalemate}) 3. Rd3+ Kf2 (3...Kxd3= {stalemate again}) 4. Rxb3 Kg2 5. Kxc2 Kxh2 6. Rb7 Kg2 7. Rh7 h2 8. b4 h1=Q 9. Rxh1 Kxh1

So, those two ideas for white are enough to guarantee the draw.

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  • 5
    Very nice. I didn't see that the Rook's lack of a diagonal move allowed another stalemate opportunity.
    – Tony Ennis
    Jun 26 at 15:10
  • 1
    The main line isn't complete. We need to consider 2...Bg5 and 2...Bh6.
    – RoundTower
    Jun 26 at 22:36
  • 1
    @RoundTower They are trivially met by Rd5 and Rd6 threatening to take the bishop
    – Brian Towers
    Jun 26 at 22:43
  • 1
    If White chooses a knight, isn't Bb4 followed by Bd2 a much easier mate? Jun 27 at 15:54
  • 1
    @JosephSible-ReinstateMonica You're right. If I'd used an engine that would have been obvious to me. I feel I get much more benefit by trying to use my own brain rather than become over reliant on the computer
    – Brian Towers
    Jun 27 at 15:59

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