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
royalty Belfort

R62 Problemesis 28, Aug 2002 (version)
Frank Christiaans &
Henk Boumeester,
version A.G.Buchanan

R61 Problemesis 28, Aug 2002
Dedicated to Étienne Dupuis
R60 Problemesis 28, Aug-2002
(16+16) PG in 11.5 (16+16) PG in 8.0 (16+16) PG in 16.5
awaybase promoted 
rook Belfort
knight Belfort
rook Belfort
Thierry Le Gleuher version A.G.Buchanan

R63 Problemesis 28, Aug-2002
R129 Problemesis 37, Feb 2004
Joost de Heer

R40 Problemesis 23, Oct 2001.
(11+11) PG in 12.5 (11+12) PG in 14.5. (14+13) PG in 8.0
knight Belfort
bishop Belfort
Thierry Le Gleuher

2428 Phénix 46, Nov 1996

Joost de Heer
R90 Problemesis 33, Jun 2003
(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.


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