No. 11, Jul-Sep 2000

R0044 -

StrateGems 11, Jul-Sep 2000

The last moves were: -1. .. f4xRg3 -2. Rh3-g3 g5xRf4 -3. Rf3-f4 g6-g5 -4. Bb8-c7 Bc7-d8. (White captures: a6xb7=B; bxc->c8R; White promotions: b8B, c8R, c8R; White capture: hxg->g5xh6->h7; Black captures g6->g5xf4->f4xg3; c7xd6)

R0045 -

StrateGems 11, Jul-Sep 2000

If the position is as it "appears", then the bBd8 must be promoted. Black has only made one capture, so the only place where the bB could have been created is on g1. On g1, however, the bB could not have escaped. Therefore, the position is illegal unless Black is really playing up the board and the bK is on h1!

Now, assume that the board is set up correctly. If it is White's turn, then Black must have just moved. Neither the bR nor the bB could have just moved, so Black must have just moved a pawn. Any pawn move must have been a capture. The only possibilities are axb2, fxe5, and fxg2. The answer can be found by examining the pawn structure around the bK. With White playing up the board, this is an ordinary structure. But with Black playing up the board (and having only made one capture), this structure is difficult to arrange. In fact, the only way to arrange this structure is for Black to have captured White's h-pawn and then to have run his own pawn to h2 so that White could capture gxh3 and Black could move his g-pawn to g2. Could the White h-pawn have captured off of the h-file and promoted, to be captured elsewhere? White has made seven captures and at least one is required to play gxh3. If the White h-pawn captured off the file, then that leaves White with five captures and Black with one capture to arrange the pawn structure to the left of the f-file. If Black has just captured, then this is impossible. Similarly, if the White h-pawn was captured on the h-file, then the position is legal, but Black cannot have just captured. It is clear that Black cannot have just played a capture and, since he cannot have played any other moves, Black cannot have just moved. Therefore, it is Black's turn, and all of Black's moves allow immediate mate:

1. ... Rf1/Bf2/Bg3 2. Rf1/Nf2/Ng3#

R0046 -

StrateGems 11, Jul-Sep 2000

R0047 -

StrateGems 11, Jul-Sep 2000

Tries in 11: 1. Nc2 2. Nb4 3. Ka5 4. Ba7 5. Kb6 6. a5 7. a4 8. Ka5 9. Qe6 10. Qa6 11. Bb6 ab4#, or 1. Nc2 2. Nb4 3. Bc6 4. Kb5 5. Kc5 6. Bb5 7. Qe6 8. Qc6 9. Rd5 10. Rf6 11. Rfd6 ab4#

In the diagram position, b2xa3 is illegal: it would require 7 captures,
and there are only 6 missing black pieces. The four legal last moves
in the diagram position are a2-a3, b2-b4, Kb2-c3 and g4xh5. Three of
those are eliminated by the first two moves:

1. Qg4 2. Ra2. Now the last move could've been Kc2-c3 or Kd2-c3, before
that was b2xa1=N. 3. Rdd2. But now only b2-b4 could've been the last
move. 4. cb3 ep The last move was b2xa3. 5. Ka5 5. b2? would leave white
without a last move. 6. b2 7. b1=B 8. Bc2 9. Ba4 10. Qb4 ab4#.

P0060 -

StrateGems 11, Jul-Sep 2000

Dedicated to Gianni Donati

1. b4 g5 2. Bb2 Bh6 3. Bf6 ef6 4. h4 f5 5. Rh3 Nf6 6. Rc3 OO 7. Rc6 dc6 8. e3 Qd6 9. Bb5 cb5 10. c3 c5 11. Nd5 Nc6 12. Nc7 Rb8 13. Na6 ba6

P0061 -

StrateGems 11, Jul-Sep 2000

1. 1. e4 a5 2. Bc4 a4 3. Bb3 ab3 4. f4 ba2 5. f5 and now:

a) 5. .. ab1N 6. Ra6 Nd2 7. Rg6 e6 8. f6 Be7 9. fe7 Nf6 10. h3 Rf8 11. ef8B Nb3 12. Be7 Nc1 13. Bd8 Kd8 14. Qc1

b) 5. .. ab1=Q 6. Ra6 Qc1 7. Rg6 e6 8. f6 Be7 9. fe7 Nf6 10. h3 Rf8 11. ef8=R Ke7 12. Rd8 Qd2+ 13. Qd2 Kd8 14. Qc1

P0062 -

StrateGems 11, Jul-Sep 2000

1. Nc3 h5 2. Ne4 h4 3. Ng3 hg3 4. Nf3 gh2 5. Rg1 hg1B 6. d3 Bh2 7. Qd2 Bd6 8. Qf4 Bc5 9. Nd2 d6 10. Qf7+ Kd7 11. Qf8 Kc6 12. Qf6 Be6 13. Qc3 Bb3 14. ab3 Nd7 15. Ra4 Nf6 16. Rh4 Qd7 17. Rh1 Rh4 18. Nb1 Nh6 19. Bf4 Rh8 20. Kd2 Nfg8

P0063 -

StrateGems 11, Jul-Sep 2000

1. f4 Nf6 2. f5 Nd5 3. f6 Nc6 4. fe7 f5 5. ed8=N Bd6 6. a4 Bg3 7. hg3 f4 8. Rh5 f3 9. Rg5 h5 10. a5 h4 11. a6 h3 12. ab7 h2 13. ba8=N h1=N 14. Nb7 Kf7 15. c4 Re8 16. Nc3 Re3 17. Ne4 Rc3 18. e3 f2 19. Ke2 Rc2 20. Qe1 fe1=N 21. Nf3 Ng2

P0064 -

StrateGems 11, Jul-Sep 2000

1. g4 c5 2. g5 c4 3. g6 c3 4. gh7 g5 5. h4 g4 6. h5 g3 7. Rh4 g2 8. Nh3 g1=B 9. f4 Bd4 10. e3 cb2 11. Ba6 ba6 12. d3 Bb7 13. Nd2 Be4 14. Nf1 Bg6 15. f5 ba1=B 16. fg6 f5 17. g7 f4 18. gh8=B f3 19. Be5 f2 20. Ke2 Kf7 21. Qe1 fe1=B 22. h8=B Bec3 23. Bhf6 Bg7 24. h6 Qf8 25. h7 Nh6 26. h8=B Kg8 27. Bb2