"La Donna è mobile? ... ...Eppur si muove!"
Henrik Juel: Orig. bQ never moved and was captured on d8. bQe8 is orig. Pa7 who played axRb-b3xBa2-a1Q; her first move was Qa2. -1.. Qd8:Q -2.Qf8 Kc2 -3.Qe8 Bf8:S -4.Sf5 g7 etc. Super problem, but I prefer the trickier stipulation question 'First move by bQ?' or 'First and last move by bQ?'. (2003-10-13)
Henrik Juel: This masterpiece deserves a detailed solution, now using KDTLSP for the men.
-1... Dd8? does not work, because then White is forced to retract Pc3, locking the SW corner; so the black queen captured a white officer on e8, but which one? An L does not help, and a T may be difficult to extract, so the captured officer was probably D or S. Let us try S, which is easily extracted: -1... Dd8xSe8? -2.Sd6 Kc2. The NE corner can be opened only by starting with retracting Lf8xg7, and uncapturing D, T, L, or P locks the corner, so Black has played Lf8xSg7; but now we need to explain how White got three knights, so it seems better to abandon the try. (2012-05-26)
Henrik Juel: Starting from scratch: -1... Dd8xDe8 -2.Df8 Kc2 -3.De8 Lf8xSg7. When Sg7 is retracted, Black must retract a P to g7 to continue opening the corner; g7xf6 or g7xh6 make it impossible to get Kf7 out, so we continue: -4.Sf5 g7, and now Kc2 is retracted to e5, allowing Kf7, Dd8 to be brought home to e1, d1. Looking at the NE corner again, we see that Th8 must be promoted, requiring two captures by white pawns; if Sg8 is also promoted, we need two more captures by white pawns, which is impossible (although four black men are missing), because [Ta8] could not have reached the NE corner; so Sg8 came in from f6. This implies that [Dd8] was captured early in the game, making room for the black king on d8, allowing White to play Sf6-g8. We also deduce that Dd8 is not original, but promoted, and since only [Lf1,Th1] could have been captured by [Pa7], the promotion happened on a1. Now the cat is out of the bag; retract Ta2 to b1, Dd8 to a1, Ke5 to d8, and Pf6 to f7, and continue the retroplay with -22.Sf6 a2-a1=D -23.Tg8 Th8 -24.h7xSg8=T b3xLa2 -25.g6xSh7 a4xTb3 etc.
It is amazing that the innocent-looking diagram position forces such a rich resolution, and I find it appealing that the solution has a suitable level of difficulty, neither trivial nor hopeless. The discovery that the black queen in the diagram is promoted should not be given away by the stipulation question, which ought to be something like 'First move by black queen?' (and maybe the author used just this in his original 1943 version). (2012-05-26)
Henrik Juel: The PDB system forced me to divide my comment above.
A silly typo: 'allowing Kf7, Dd8' should be 'allowing Kf7, De8', of course (2012-05-26)
Henrik Juel: In the Fairy Chess Review no. 10, February 1947, p. 76, the problem was reproduced (in notation) with the stipulation question 'What was Black's first queen move?' (2012-07-10)
comment