Lasker's Pin

This brilliant problem was conceived by Emmanuel Lasker,
the 2nd official World Champion of chess.


White to move and win!

White will manuever into a position which allows him to
sacrifice his rook for the sake of promoting his pawn.
Once this is learned, it will be easy enough to remember
should you ever manage to reach the initial position in a game.

1. Kb7 ...
White guards the c8 queening square,
forcing Blacks reply.

... Rb2+

2. Ka7 ... Rc2
also forced

3. Rh5+ ... Ka4
{if 3 ... Kb4?? 4. Kb7! wins immediately.}

4. Kb7 ... Rb2+

5. Ka6 ...
White's King and Rook act in concert to
push the Black king back to the 2nd rank.

... Rc2

6. Rh4+ ... Ka3

7. Kb6 ...
By guarding c7, White threatens to
sacrifice his Rook for the h pawn.

... Rb2+

8. Ka5 ... Rc2

9. Rh3+ ... Ka2
Black is now 'safe' from
checks by the White Rook.

position after 9 ... Ka2
..
White to move ...


10. Rxh2!! ...
The point! A horizontal pin on the
2nd rank ensures the promotion of
White's pawn.

1-0

This is where many authors say, "and wins" - but it isn't as easy as that.
Queen vs. Rook positions are among the most difficult wins to successfully
execute in chess.

After

... Rxh2,

Chessmaster 9000 saw a forced mate (in 20!) and blitzed
out the solution at lightning speed.

[Date "2-13-2008"]
[White "Chessmaster"]
[Black "Chessmaster"]

11. c8=Q ... Kb1
12. Qf5+ ... Rc2
13. Qe4 ..... Kb2
14. Kb4 ..... Rd2
15. Qc4 ..... Rc2
16. Qf4 ..... Re2
17. Qf3 ..... Rc2
18. Qf6+ ... Ka2
19. Qe5 ..... Rf2
20. Qd5+ ... Kb1
21. Qd3+ ... Ka2
22. Kc3 ..... Rb2
23. Qd1 ..... Rh2
24. Qb3+ ... Ka1
25. Qb8 ..... Re2
26. Qa7+ ... Kb1
27. Qb6+ ... Ka2
28. Qa6+ ... Kb1
29. Qxe2 ... Kc1
30. Qf1# .... 1-0

However in a competitive situation even a very strong human player would be hard-pressed to bring this game to a successful conclusion against best play (a computer program with endgame databases enabled).

Of course in a practical situation the task is not to find mate in 25 but the win of the Rook in 50! How difficult is that? Here's an idea - at a time control of 20 minutes with a 5 second increment added with each move, Chessmaster 9000 playing White with its endgame databases disabled had to settle for a draw (by 50 move rule) in play against its unaltered self defending with Black from the position after c8=Q.

[Date "2008.2.13"]
[White "Chessmaster with endgame databases disabled"]
[Black "Chessmaster"]
[TimeControl "20 min + 5 sec"]
[FEN "8/2P5/8/K7/8/8/k1r4R/8 b - - 0 1"]

1...Rxh2 2.c8=Q Kb1 3.Qf5+ Rc2 4.Kb4 Kc1 5.Kb3 Re2 6.Kc3 Re3+ 7.Kd4 Ra3
8.Qb5 Ra2 9.Ke4 Ra3 10.Qc5+ Kb2 11.Qb6+ Rb3 12.Qd6 Kc2 13.Qd4 Rc3 14.Qd5
Rg3 15.Qa2+ Kd1 16.Qf2 Rc3 17.Qb2 Rg3 18.Kf4 Rh3 19.Qg2 Rb3 20.Ke5 Rb4
21.Qc6 Kd2 22.Qc5 Ra4 23.Kd5 Rf4 24.Qd6 Ke3 25.Qh6 Kf3 26.Qe6 Ra4 27.Qe1
Ra8 28.Qe4+ Kf2 29.Kd6 Rd8+ 30.Ke7 Rd2 31.Kf6 Rd8 32.Kf7 Rd1 33.Kg6 Re1
34.Qf4+ Ke2 35.Qd4 Rf1 36.Kg5 Rd1 37.Qe4+ Kd2 38.Kh4 Kc3 39.Kh5 Rd3
40.Kg5 Rd4 41.Qe5 Kc4 42.Kf6 Rd5 43.Qe6 Kd4 44.Qe7 Rc5 45.Qb7 Rc3 46.Qg2
Re3 47.Qc6 Rc3 48.Qb7 Rc5 49.Qa8 Rc4 50.Qf3 Rc3 51.Qh1 Rc5 52.Qg2
1/2-1/2

So think twice before resigning a lost game -
nobody ever drew a game by resigning!

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