The Retrograde Analysis Corner

StrateGems

No. 9, Jan-Mar 2000

R0038 - Noam Livnat

StrateGems 9, Jan-Mar 2000

Consider (a) the blocked structure on the 7th and 8th ranks and (b) the last 6 moves:

(a) The block:

The bBf8 was captured at home. The two WBs were promoted on g8 and h8 by wPh2 and wPe2, which captured the 4 remaining black pieces. bPh7xg6 was played long ago. The WPb7 came straight from b2.
The WK entered the 8th row via a6 and b7, while the bK waited outside. The block was sealed after bNe6-f8, wKc8-d8. Black's final move, Kb7-b8, was made when bRa8 was in it's place, hence a white piece had to be blocking the bR-wK open line, either on b8 or on c8.
On c8: clearly not a wQ,R or B (bKb7-b8 would have been impossible), => it was a wN. On b8: not a wQ since the bK couldn't have entered b7, nor a wB since there are no free wPs to promote: => it must have been a wR (wRc8-b8+ bKb7:Rb8) or a wN (with another wN on c8, i.e.: wNa6(c6)-b8+ bKc6(a6)-b7 with bKb7:Nb8

(b) The last 6 moves:

Only after bKb7-b8 were white moves: Bc8, Pb7 made. Black's moves were with it's Pc3. A careful observation will prove that the wNb5 position forces 4 white last moves: 2 with the B, one with the N, one with the P. Black Pc6 must have started on the 6 row. If from b6 (capturing, say, WBc5), White would need an extra Pb5-b6 move: impossible. So, coming from c6, it leaves no R or N capture for the bK to make on b8 (bPb7xc6 and bPh7xg6 captured white-squares white pieces, namely the R and the N, and NOT the wBc1!).
So: wK on d8, wN on c8, wB on c4(d3), wPb6 - bKa6 (under check), Ra8, Pc6. And now: bKa6-b7 wBc4-a6+ Kb8 Nd6 c5 Bc8 c4 b7 c3 Nb5.
Now, after wKc8-d8 was made, wNd6(b6) came to c8 WITHOUT CAPTURING. So bRa8 couldn't have been there at the time (b7xc6 being done a long time ago, and having no extra pieces, white or black, to block on b8.)
Conclusion: Only after wNc8 sealed the block was bRb8-a8 played, and no other piece was there to visit b8 afterwards.

So the bRa8 was the last piece to visit b8 before the bK.

R0039 - Paul Raican

StrateGems 9, Jan-Mar 2000

In the try: Last moves were: -wP: d3xPc2, -Nh3: d3xNc2, -Nb1: d3xBc2 Bb1-c2, -bPd6: Kb5-a4 Rd8-d5. But the position is legal! Last moves were Kb5xNa4(+wNb1) Nc5-a4.

P0050 - Michel Caillaud

StrateGems 9, Jan-Mar 2000

1. h4 a5 2. h5 a4 3. h6 a3 4. hg7 ab2 5. a4 h5 6. Ra3 Rh6 7. Rf3 Rc6 8. Na3 Nh6 9. g8=R b1=R 10. Rg4 Rb5 11. Re4 Rd5 12. g4 b5 13. g5 b4 14. g6 b3 15. g7 b2 16. g8=R b1=R 17. Rg2 Rb7

P0051 - Mark Kirtley

StrateGems 9, Jan-Mar 2000

1. e3 d5 2. Be2 Bh3 3. Bh5 Qd7 4. Qg4 Qa4 5. Nf3 Nc6 6. OO Rd8 7. Kh1 Rd6 8. Rg1 Rf6 9. Qe6 b6 10. g4 Bf1 11. Rg3 Ba6 12. Rh3 Bc8

P0052 - Mark Kirtley

StrateGems 9, Jan-Mar 2000

1. h4 Nf6 2. h5 Ne4 3. Rh4 Nd2 4. Rg4 Ne4 5. Qd6 Nc6 6. Qh2 d6 7. Bf4 d5 8. e3 d4 9. Bb5 d3 10. Nf3 d2 11. Ke2 d1=R 12. Nd4 Rd3 13. Nd2 Rc3 14. Rh1 Rc5 15. Qg1 Rd5 16. Qd1 Rd7 17. Bd6 Nb8 18. Bd7

However, this move order isn't unique: 1. h4 Nf6 2. h5 Ne4 3. Rh4 Nd2 4. Nf3 Ne4 5. Qd6 Nc6 6. Qh2 d6 7. Bf4 d5 8. e3 d4 9. Bb5 d3 10. Rg4 and the rest goes as in the intention.

P0053 - Satoshi Hashimoto

StrateGems 9, Jan-Mar 2000

1. Nc3 e5 2. Nd5 e4 3. Nf6 Qf6 4. Nh3 Qf3 5. Nf4 f5 6. Nd5 Kf7 7. Nc3 Kg6 8. Nb1 Kh5