[Retros] Stuttgarter Zeitung: Christmas Contest

[Jens Guballa]

Dear retro friends,

here are the solutions for the Christmas Contest of the Stuttgarter
Zeitung:

I shortened the translation, the original text with some more comments
given by the solver is available here (only in German):

http://www.kaniaverlag.de/htm/Weihnachts2008.html#1


A: Obviously, -Ng2, then 1. Rgg2 and Qf8#. 
Indeed, there is another solution: -Pd5. Black has no last move and is
in Zugzwang: 0. ... Ke2: 1. Qd8 Kf3/Kf1 2. Qd1# or 0. ... Kg4: 1. Qa5
Kf3/Kh3 2. Qh5.


B: White retracts Kc8xPb7. The white king moved to c8 via d7/d8, thus
black cannot castle anymore. Therefore the solution is 1. f5-f6 and 2.
Rd8#. The retraction Kc8-b7 is not suffcient because the last black move
could have been h7-h6 (or g7xh6), and thus black has the right to
castle.


C: Besides the given example (+wBa1, +bPd5, last move was e5-e6+) there
are the following solutions:
a) +bPg7, +wRg8: last move was f7xNg8=R#. The captures piece on g8 can
be only a knight.
b) +bPg6, +bBh6: last move was g7-g6+.
c) +wPf4!, +wBa1: last moves were d5xPe6 e.p+, e7-e5, d4-d5+, e5xXf4.
The pawn on f4 forbids the solution e5-e6+, because black has no last
move in that case.


D: Candidates for the last black move are only b7-b6 and e7-e5. After
+Nc8 b7-b6 is illegal: Two promoted black pieces are on the board, but
only one black pawn is missing. The position with e7-e5 is legal, bBf8
was captured on f8, the bRR and the bQ were captured by the white pawns.
The black f-pawn captured the white knight and promoted on e1 or g1.
Thus 1. f5xe6 e.p.+ h7xg6 2. Qf7xg6#.

Second solution: +bBb8. Black has no last move and checkmates with 1...
c7-c6+ 2. Kd5xe5 Bb8xd6#. The last move b7-b6? requires that the bBb1 is
a promoted piece, but there are not enough white chess men missing. The
white pawns a+b have not promoted (to be captured by the black f-pawn), 
as too less material is available for a cross capture of the pawns.
And e7-e5? is not possible, because then the bBb8 must be a promoted
piece (on a1/c1), but for that too much material is needed.

Failing attempts: 
+bBc8?: Last move could be b7-b6, white b-pawn promoted (b6xRa7 and
a7-a8=N), and the black f-pawn captured the two knights and promoted
into the white squared bishop.

+bBg8?: This position is only legal if black has the move, but in this
case there is not checkmate.


E: To give checkmate with Rd8# another piece must be uncaptured: 1.
g5xBh6! (bishop has promoted on g1, three pieces were captured)
f6-f5/a7-a6 (f7-f5? illegal due to white's king position, b6-b5? or
b7xNa6? or e6xNf5? illegal due to missing material for the captures) 2.
a4-a5 a7-a6/f6-f5 3. c2xBb3! Ba2xNb3+ (Ba2xBb3? is illegal because the
square of the bishop has the wrong color) 4. Nd4-b3 (4. Na5-b3? Bb1-a2+
5. Nb7-a5/Nc6-a5 leads to a retro stalemate) Bb1-a2+ 5. Ne6-d4 (5.
Nc6-d4? leads to a retro stalemate, this trick was overlooked by
several strong solvers) no retro stalemate (Ba2-b1), and now forward:
1. Rd7-d8#.

Failing attempt: 1. a4-a5? b6-b5!! (1... b7xNa6? 2. Nb8xBa6 ... 3.
Nc6-b8 and forward 1. Rd7-d8#; 1... e6xNf5? 2. Nd4-f5 a7-a6 3. Nc6xXd4
and forward 1. Rd7-d8#) and 2. c2xBb3? is illegal, because the captures
must have been bBa2xNb3+, bPb7xNa6 and bPa7xBb6 (only this way the white
rook can enter the black camp), but this requires that white has
captured all black missing chess men, including the black h-pawn. But
this pawn could not have left the h-file as the wRh1 is out of reach.

71 solver send their solutions, 45 of them made it to the drawing lot
(problems A + B solved correctly). 

Here are the winners:

1. Irma Maurer, Rupertshofen (Falk navigation system)
2. Ronald Schäfer, Aalen (Apple I-Pod)
3. Jens Guballa, Tamm (Panasonic mirco wave grill)

Winner of the expert contest (solving all five problems correctly) are
the following eleven solvers: Silvio Baier (Dresden), Dietmar Fauth
(Munic), Andrey Frolkin (Kiew), Norbert Geisler (Munic), Jens Guballa
(Tamm), Olli Heimo (Helsinki), Kurt Lorenz (Marbach), Thomas Lutzius
(Stuttgart), Frank Moralee (Brough/England), Rolf Schreiber (Stuttgart),
Klaus Wenda (Vienna).

The following solvers were close to the correct solutions: Hans Bergmann
(Aalen), Gerson Berlinger (Friedrichshall), Randolf Eilenberger
(Dossenheim), Nils Empacher (Stuttgart), Martin Kummer (Karlsruhe),
Markus Knapp (Großeicholzheim), Peter Michael (Goslar), Mario Richter
(Berlin), Ronald Schäfer (Aalen) and Bernd Schwarzkopf (Neuss). They all
will also receive a book price.



Best regards,
Jens