BELFORT PROOF GAMES
The "Belfort (Champagne)" theme is named after the location of the 1994 FIDE Congress. There is a regular Champagne Tourney (composition tourney for proof games) held at these congresses, and at Belfort, the theme was "At least two units stand on the home square of a similar unit of the other colour". (The awards for that Tourney can be found here.)
| capture-free symmetric knight Belfort |
capture-free symmetric bishop Belfort |
capture-free royalty Belfort |
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| {A} A.G.Buchanan R62 Problemesis 28, Aug 2002 (version) |
{B} Frank Christiaans & Henk Boumeester, version A.G.Buchanan R61 Problemesis 28, Aug 2002 Dedicated to Étienne Dupuis |
{C} A.G.Buchanan R60 Problemesis 28, Aug-2002 |
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| (16+16) PG in 11.5 | (16+16) PG in 8.0 | (16+16) PG in 16.5 |
| awaybase promoted rook Belfort |
promoted knight Belfort |
original rook Belfort |
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| {D} Thierry Le Gleuher version A.G.Buchanan R63 Problemesis 28, Aug-2002 |
{E} A.G.Buchanan R129 Problemesis 37, Feb 2004 |
{F} Joost de Heer R40 Problemesis 23, Oct 2001. |
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| (11+11) PG in 12.5 | (11+12) PG in 14.5. | (14+13) PG in 8.0 |
| symmetric knight Belfort |
promoted bishop Belfort |
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| {G} Thierry Le Gleuher 2428 Phénix 46, Nov 1996 |
{H} Joost de Heer R90 Problemesis 33, Jun 2003 |
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| (13+13) PG 14.5 | (10+12) PG 13.0 |
Following that tourney, a number of other composers have
explored this theme. Étienne
Dupuis' site examines 4 cases:
(i) All 4 rooks appear swapped,
(ii) All 4 knights appear swapped,
(iii) All 4 bishops appear swapped,
(iv) The 4 "royalty" (kings & queens) appear swapped.
Thematic pieces in Belfort may be original or promoted. Aesthetically, I feel like it if either all four pieces are original or none of them are. Étienne's page focuses on the former idea, but both are worthy of attack.
So that gives 4x2 = 8 tasks.
original unit Belfort
Where the pieces are original, it seemed to me attractive to look for capture-free [1] PGs. That's my main objective, even at the cost of a move or two. For bonus points, I also wanted to bring out the latent symmetry of the position where possible, but not at a cost in speed.
I have not yet managed to produce a capture-free rook Belfort. If you allow captures, see what Joost de Heer could achieve in {F}. Also it's hard for tools to reason effectively about rooks avoiding advancing but non-capturing rook pawns.
Thierry's {G} achieves a mirror-symmetric position in an odd number of moves (clap, clap, see here for others). He mixes original with promoted pieces however, so this is not quite comparable.
promoted unit Belfort
The notion of "at home" (aka "homebase") seemed to me to chime with this theme, as it brings the thematic units into sharper relief. So let's define the notion of awaybase. This is a generalization of homebase, where each unit is on the home square of a similar unit of the its own or the other colour. I aim to do this in the minimum number of moves. Symmetry is not an objective.
The rook case is solved, but that's by far the easiest one. The knight and bishop cases are very close See {E} and { H}.
And then there are Belfort pawns, which I haven't tackled at all, but somehow they are less appealing. Maybe once I get into it... Anyway: a priori, there might be as many as 16 simultaneous Belfort pawns! (Each side could cross-capture twice.) Exactly what is realizable though in the curious world of proof games, I don't know. And then there is question of mixing and matching other types of Belfort unit in the same diagram.
[1] A happy oxymoron.