R Puzzle: The Hall of Chess

by Dean Sturtevant

First of all, note that Black made no captures, and White made four. One of White's d pawns made a capture. Black's original black-squared bishop was captured on its home square, so the one on the board promoted. Since the pawn had to have marched straight down the board, it was the c pawn. White's c pawn had to make a capture to get out of the way. White's b pawn also had to make a capture in order to promote. That accounts for all the captures (3 pawn captures, plus the capture of the bishop).

The last move had to be Rf6-f5+. It couldn't have moved from g5 or h5, because that would have involved making a capture.

The previous move had to be Pf5-f4. (The only other pieces with freedom to unmove would have unchecked the White king).

The one before that had to be Nf4-d5+. (It couldn't be Bg1-h2, because that would have left Black retro-stalemated).

Before that, Pd5-d4.

Before that, Rb2-b6+ (a Q move would retro-stalemate Black. The Black pawn at d5 can unmove neither to d6 (unchecking) or d7 (because the Black white-squared bishop would then have been captured on its home square).

Before that, Ba5-c7.

Before that, Pc7-c8(B)+. (It wasn't Pc7xb8(B)+ or Pc7xd8(N)+ because the c pawn had to have already made its capture to let the Black c pawn by).

Before that, Bc3-a5.

The previous move had to be made in a response to a check (see flavortext). It could have been Kb4-c5, Kc4-c5, Pb6xc7, Pf3xe4, or Pf2xe3.

Thus the moves were

  1. (a)Kb4-c5, (b)Kc4-c5, (c)Pb6xc7, (d)Pf3xe4 or (e)Pf2xe3
  2. Bc3-a5
  3. Pc7-c8(B)+
  4. Ba5-c7
  5. Rb2-b6+
  6. Pd5-d4
  7. Nf4-d5+
  8. Pf5-f4
  9. Rf6-f5+

As for the statements,

By (a) the Albanian made #5.

By (b),(c),(d),(e) and (f), #6 was made by the Basque, Estonian, or Burmese. If the Basque made #6, then by (h), the Estonian made #1(a,b, or e). If the Estonian made #6, then by (h) and (g), the Basque made #1(b). If the Burmese made #6, then by (i), the Estonian made #1(d) or #8. The latter is not possible by consideration of (g) and (h). Thus, move #1 was made by the Basque, Estonian, or Burmese (and not 1(c)). So by (e), the Italian made #4, and by (b), the Romanian made #2. The Korean is left making move #3, and the Turk, #7. The Swede could now only have made #9. The only possible move triple for {Basque, Estonian, Burmese} with the remaining moves #1,#6,#8 is {#1(b),#6, #8}.


1. Kc4-c5           Basque
2. Bc3-a5           Romanian
3. Pc7-c8(B)+       Korean
4. Ba5-c7           Italian
5. Rb2-b6+          Albanian
6. Pd5-d4           Estonian
7. Nf4-d5+          Turk
8. Pf5-f4           Burman
9. Rf6-f5+          Swede

The flavortext suggests that the way the moves are notated is important. According to the guidelines of FIDE (the international chess federation), "FIDE recognizes for its own tournaments and matches only one system of notation, the Algebraic System," which is the system used above, in which "each piece is indicated by the first letter, a capital letter, of its name." However, "For the first letter of the name of a piece, each player is free to use the first letter of the name which is commonly used in his country."

Using a web site such as http://www.chess-poster.com/english/notes_and_facts/name_of_pieces.htm, which has a table listing the names of pieces in various languages, we can write the moves the way the people making the moves presumably would (but NOT using the convention that pawns aren't notated). In that case, the moves become:

1. Ec4-c5           Basque
2. Nc3-a5           Romanian
3. Pc7-c8(B)+       Korean
4. Aa5-c7           Italian
5. Sb2-b6+          Albanian
6. Sd5-d4           Estonian
7. Af4-d5+          Turk
8. Nf5-f4           Burmese
9. Tf6-f5+          Swede

Reading down the column naming the pieces: ENPASSANT.