Recounstructing a chess game

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21st September 2009, 05:21am

by sanjayd1998
Bangalore India

Member Since: Nov 2008
Member Points: 169

Here is yet another type of puzzle - a reconstruction problem. These depend as much on logic as skill at chess, but for that reason they offer a welcome change from the endless 'Find the Combinations' puzzles so beloved of chess magazines. This is the position after Black's 14th move, what was the game?

The first step is to count the number of moves required for Black's pieces to arrive in their diagram positions. Then it will be possible to determine the fate of the two missing black pieces. The next stage is to determine when the pawn on d7 was captured, and when the rook on a8 disappeared. A final leap of the imagination will be necessary for the complete solution.

Black's bishops have made at least three moves, his pawns five, his queen two, his c4-rook three and his knight one - total 14. Thus neither the b8-knight nor the d7-pawn ever moved, and both must have been captured on their original squares by white knights. It follows that the rook on c4 started life on h8.

Now we have to work out the order of Black's moves. Which moves can Black play before the d7-pawn is captured? Note that ...e6 must come after ...Bh3, and ...Ne7 must follow ...e6. This releases the h8-rook to move to c4. Therefore the Ng8, Rh8 and Pe7 cannot move until after White plays Nxd7. Black's queen must have reached h5 via d5, g5 or h4, so Black cannot play ...g5 until after at least one queen move, or else the queen cannot reach h5 in two moves. Thus the Pg7 and hence also the Bf8 cannot move until after Nxd7. In other words, the only moves Black can make before the d7-pawn is captured are ...f5, ...f4 and ...f3. Then Black runs out of moves, so White must play Nxd7 by move three. This determines the first few moves.

Now we have to work out how the a8-rook is taken. In the final position White has a knight on g1, and since f3 is now blocked it must arrive there via h3. The obvious plan is 4 Nb6 5 Nxa8 6 Nb6 7 Nd5 8 Nf4 and 9 Nh3, but in fact this is impossible. The reason is that with this sequence Black cannot play ...Bh3 until move 10 at the earliest, but at least five moves (...e6, ...Ne7 and three with the rook) must follow ...Bh3, and there is no time for these. It follows that it is the knight on b1 which heads for h3. So White must continue 4 Nb6 (the d7-knight must move, because Black has no more pass moves) and then play the Nb1 to g1 (via h3), which takes us up to move nine (Black's ninth move must be ...Bh3), finally 10 Nxa8 and back to b1 consumes all the white moves.

Black's last six moves are 9...Bh3, 10...e6, 11...Ne7 and rook to c4. Since the pawn stays on e7 until move 10, the black queen must reach h5 via d5. This must occur before ...g5, which releases the f8-bishop for ...Bg7-c3. Now we have completely determined the order of Black's moves.

Voila!
Looking at the diagram position, it is not obvious that White's knights must have changed places.

QUOTE

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