No. 120 , Jan. 1997 - SOLUTIONS
3682 - Leonid Borodatov
White captures are cxb, dxc, exd, gxfxe, hxgxf, and the a-pawn on
its own line. The capture on the b-line was necessarily the missing
black b-pawn, since that pawn couldn't have promoted without a capture.
Black has no possible last move. To give black a retro-move, white's
last move must've been b2-b4, and play before that was Qe3-a3
So mate in 1 with 1. .. cb3#!, and not 1. Ra3? or 1. Qb2?.
3683c - Stanislav Vokal
Suppose white can castle. The bishop on h3 is the promoted a-pawn,
and this pawn needs 5 captures to promote, and keep white's castling
intact. Together with the capture on the g-line these are all the captures
black did. White's pawns captured 4 times, and together with the missing
bishop from c8, these are all the captures white did. So the h-pawn
had to promote on h8 to get to a square it could get captured. So black
1. OOO! ~ 2. Ra3 3. Ra8#
3684 - Alexander Zolotarev
Last moves were: -1. .. f6xBe6 -2. Bc8-e6 f4xNg3 -3. c7-c8=B e5xNf4
-4. b6xRc7. Further retracting involves unpromoting the two uncaptured
knights on c8, uncapturing c7xRd6 and d6xRe5, uncapturing a black-squared
black bishop by one of the white pawns on the queen wing, unpromoting
the two uncaptured rooks on g8, bringing back the uncaptured bishop
to f8, and uncapturing a white rook on f6.
The position can be unlocked with only one queen move: Qh1-h2.
3685 - Jean-Michel Trillon
3686 - Thierry Le Gleuher
3687 - Thierry Le Gleuher