7 bishops of the same colour defeat 8 queens.

[Ajedrecista]

Hello:

How can this be possible? With some imagination, of course. I composed a position with a mixture of things: a kind of Alekhine's guns for both bishops and queens, the winning side giving checks in every move (I am talking about a #13) and a final checkmate ressembling an Anastasia's mate. The moves annotated with exclamation marks mean that these moves are the only ones to give the shortest checkmate, when there are more possible moves (or the only ones to delay more the checkmate from losing side POV, when there are more possible moves):

[pgn][Event ""]
[Site ""]
[Round ""]
[Date "2026.08.07"]
[SetUp "1"]
[FEN "1B1q3q/B1B2K2/1q1B3r/4Bbk1/qq1qq1pb/B4qPR/nB3PrQ/R7 w - - 0 1"]
[Result "1-0"]
[PlyCount "25"]

1.Bc1+! Nxc1! (1...Kh5? 2.Rxh4! Qxh4 3.Qxh4#! 1-0) 2.Bxc1+! Qde3! 3.Bxe3+! Q6xe3! 4.Bxe3+! Qexe3 5.Bf4+! Qexf4 6.Bxf4+! Qbxf4 7.Bxf4+! Qaxf4 8.Bxf4+! Qxf4! 9.gxf4+! Kh5 10.Rxh4+! Qxh4 11.Qxh4+! Kxh4 12.Rh1+! Rh2 13.Rxh2#! 1-0[/pgn]

All white moves are marked with '!'. SF 18 solves the position in few time, but I was delighted that Chest 5.2 also shines:

Code: Select all

FEN: 1B1q3q/B1B2K2/1q1B3r/4Bbk1/qq1qq1pb/B4qPR/nB3PrQ/R7 w - - 0 1

ChestUCI:
FEN: 1B1q3q/B1B2K2/1q1B3r/4Bbk1/qq1qq1pb/B4qPR/nB3PrQ/R7 w - -   (13+15)
Stellungs-Analyse:  C0/R0/K2/P15/X103   W:10/29
Suche nach Matt in 13 ...  (Hash=64MB)
  13	00:05	     461.598	641.999	+M13	Bb2c1+
Suche abgeschlossen ...  (Zeit=1.83s)
Matt in 13 gefunden !  (1 Lösung in 00:01)
 13/13	00:05	   1.272.004	695.844	+M13	Bb2c1+ Na2xc1 Ba3xc1+ Qd4e3 Bc1xe3+ Qb6xe3 Ba7xe3+ Qe4xe3 Be5f4+ Qb4xf4 Bd6xf4+ Qa4xf4 Bc7xf4+ Qe3xf4 Bb8xf4+ Qf3xf4 g3xf4+ Kg5h5 Rh3xh4+ Qd8xh4 Qh2xh4+ Kh5xh4 Ra1h1+ Rg2h2 Rh1xh2+

All in all, this was a bloody mess with lots of kills, just like the famous, hilarious scene of the parody film Hot Shots! Part Deux: counting wood in the usual way {Q,R,B,N,P}={9,5,3,3,1}, I get 42 vs 92 (sum of 134) at the start of the position, only to end 7 vs 18 (sum of 25) after 25 plies! I counted 8 consecutive captures in the given line, from 5.- ..., Qexf4 to 9.- gxf4+.

------------

Where this idea came from? I watch Graham's excellent Amateur Series Divisions once in a blue moon, few minutes once or twice a year... or even less. Well, today was one of those days and I faced an already started game that I even did not wait to end! But I had enough to think later. This was the game 392 of 126th Amateur Series Division 1 (Coda 0.9.3 vs Berserk 14_JA). The position was:

[d]4n3/3k1pr1/p3p3/Pp1pPpPp/1P1B1P1K/4P3/6R1/8 b - - 21 63

Black played 63.- ..., Nc7 and my noob alarm rang. Eh? What about 64.- Kxh5, winning a free pawn? Why black did not defend its h-pawn? I understood almost immediately: 64.- ..., Rh7#. There was a pattern that I had not seen earlier and reminded me the Anastasia's mate, though with doubled pawns instead of a knight (in this case, a black knight on e5 would cover both g4 and g6, just like black pawns on f5 and f7 do, respectively) plus the white own pawn on g5 ruining the last escape from black's rook on h-file.

From there, there was a matter of squeezing.

Regards from Spain.

Ajedrecista.

[Joerg Oster]

Very nice!

For special solvers like Chest and Gustav, this is a very easy problem
because the solution is a continuing sequence of checks.

This is Matefish's AB search:

Code: Select all

info string Starting Alpha-Beta Search ...
info time 12 multipv 1 depth 1 seldepth 1 nodes 6 nps 500 hashfull 0 tbhits 0 score cp 0 pv c7d8
info string Success! Mate in 13 found!
info time 205 multipv 1 depth 3 seldepth 25 nodes 385057 nps 1878326 hashfull 0 tbhits 0 score mate 13 pv b2c1 a2c1 a3c1 b4d2 c1d2 f3e3 d2e3 d4e3 c7d8 h8d8 e5f4 e3f4 d6f4 e4f4 b8f4 a4f4 g3f4 g5h5 h3h4 d8h4 h2h4 h5h4 a1h1 g2h2 h1h2
bestmove b2c1 ponder a2c1

With Huntsman, you can a see a pretty wild swing of the score in one iteraion:

Code: Select all

info depth 14 seldepth 20 multipv 1 score cp -3952 nodes 343563 nps 1235838 tbhits 0 time 278 pv b2c1 a2c1 a3c1 b4d2 c1d2 f3e3 d2e3 e4e3 c7d8 b6d8 g3h4 g5h5 h3e3
info depth 15 seldepth 25 multipv 1 score cp -4431 nodes 431797 nps 1281296 tbhits 0 time 337 pv b2c1 a2c1 a3c1 b4d2 c1d2 d4d2 e5f4 d2f4 d6f4 e4f4 g3f4 g5h5 h3h4 d8h4 h2h4 h5h4 a1a4
info depth 16 seldepth 23 multipv 1 score mate 13 nodes 435970 nps 1289852 tbhits 0 time 338 pv b2c1 a2c1 a3c1 b4d2 c1d2 e4e3 d2e3 d4e3 c7d8 h8d8 e5f4 e3f4 d6f4 f3f4 b8f4 a4f4 g3f4 g5h5 h3h4 d8h4 h2h4 h5h4 a1h1 g2h2 h1h2
bestmove b2c1 ponder a2c1

From -4431 cp to Mate in 13. Amazing!

[Dann Corbit]

Really fun and ingenious position!