9
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What is the most possible checkmates in one without promoted units in a position? It must all be legal, of course.

Consider this a part two of this question: How many total checkmates can you possibly make against the enemy king

Promotions are allowed in the game, but the position is not allowed to start with promoted pieces. Promotions count as one move, regardless of promotion type, per pawn.

I have found 37. I have modified the position made for the record for most no promoted units, all possible moves a forced checkmate, made by Harold Holgate Cross. (see it here: https://chess.stackexchange.com/questions/24033/a-position-in-which-checkmate-is-forced-obligatory/24067.)

EDiT: My position here is invalid due to having flaws pointed out in the comments.

enter image description here

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  • $\begingroup$ If the rook d2 moves to another square of the 2nd file, that's not checkmate as the king will be able to move to d4. $\endgroup$ – Arnaud Mortier Apr 13 at 9:43
  • $\begingroup$ I think this question is poorly worded. Perhaps "What's the largest number of checkmates in one, all from the same position"? $\endgroup$ – Acccumulation Apr 24 at 21:10
  • $\begingroup$ @Acccumulation Fixed! $\endgroup$ – Rewan Demontay Apr 24 at 21:22
  • $\begingroup$ Is it allowed to have a position with no possible previous black move? I.e. when there is no legal way to arrive at that position. $\endgroup$ – Florian F May 26 at 17:43
  • $\begingroup$ It must be legal. $\endgroup$ – Rewan Demontay May 26 at 18:01
6
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UPDATE #4: After some asking on Matplus a few weeks ago, I found that my 42 was already beaten. But I have an ego. It feels so good to have come so close! Anyhow, here’s the “new” records.

Enjoy!

Without Promotions-43

: enter image description here

The 43 Mates:

Pd2-1, Pf2-2, Ph2,1, Nc3-2, Nh4-2, Qd4-4, Kf7-6, Rg5-12, Be4-13

With Promotions-44

: enter image description here

The 44 Mates:

Pa7-1, Pd7-1, Ph7-1, Ne8-2, Qf5-4, Nd8-8, Be5-13, Rc4-14

I always knew that three pawn promotions. I just couldn’t figure it out myself. The same goes for giving the queen more moves. Another thing, quite amusing to me at the least, is that you can just add in a pawn to the 43 one to equal the record of 44 with promotions


UPDATE #3: I found 42 without extra promotions. I made that useless knight useful with 2 mates and I tacked on an extra discovered checkmate by giving the queen’s knight more freedom.

Slight Update: I found a way to keep the same result with one less pawn. I also moved the king to give the queen’s horse more room, even though it changes nothing. It’s just more elegant

: enter image description here

The 42 Mates:

Rg2-14, Be5-13, Nc5-7 Ne8-2, Qb5-2, Ph7-1, Pa7-1, Pd3-1. Pe3-1


UPDATE #2-I’ve totally beaten that 36 with an astonishing 39! So darn close to 40! Take a look! I shall heartily accept any flaws that you find!

If you could get 3 pawn promotion checkmates in a position that is similar to this, you could get 40, but due to the fragility of the set up, I severely doubt this. I was unable to do it myself.

enter image description here

The 39 Mates:

Pb7-1, Pd7-1, Pc2-1, Pe2-1, Bd4-13, Rf5-14, Ng4-6, Qh4-2


UPDATE: I have recently found a flaw Araud Mortier’s position. If the d4 bishop moves, then the black pawn can block the rook check. This also invalidated my answer as well. So I flipped the position for a new record of 36. This will no doubt be broken soon. This position is made for him.

enter image description here

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  • $\begingroup$ Very nice idea! $\endgroup$ – Arnaud Mortier Apr 24 at 20:21
  • $\begingroup$ Pd2-1, Pf2-2, Ph2,1, Nc3-2, Nh4-2, Qd4-4, Kf7-6, Rg5-11, Be4-13 = 42 mates $\endgroup$ – Florian F May 26 at 17:35
  • $\begingroup$ Actually, the rook has 12, not 11. Thx for spotting that typo there! $\endgroup$ – Rewan Demontay May 26 at 18:04
4
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Here is 36 (the 37 from the OP has flaws, see comments), contributions given by:

Bishop d4 moves: 13, Rook c2 moves: 14, Knight g4 moves: 2, Queen moves: 7

Picture:

enter image description here

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  • $\begingroup$ I just realized that if the bishop on d4, moves, then the black pawn can block. So that matrix is trash now, mostly. $\endgroup$ – Rewan Demontay Apr 24 at 20:10
  • $\begingroup$ @RewanDemontay fixed - although it's now 36. Nice job finding 42! $\endgroup$ – Arnaud Mortier Apr 25 at 12:26
  • $\begingroup$ Yep. And thank you! $\endgroup$ – Rewan Demontay Apr 25 at 13:10
  • $\begingroup$ Um, I only count 6 queen moves in your diagram. Feel free to use the one that I made for you in my answer. $\endgroup$ – Rewan Demontay Apr 25 at 13:14
  • $\begingroup$ @RewanDemontay I simply uploaded the wrong version. $\endgroup$ – Arnaud Mortier Apr 25 at 18:25
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I have 35, with the following:

Nd7: 2
Pg7: 1 (Q or B)
Rc6: 14
Nb5: 2
Re4: 14
Qf3: 2 - 4 possible queen checks leave the rook at e4 unprotected

Picture:

enter image description here

The secret to the moves here is:

Double protecting all positions around the king, so that I could move any of those pieces to check without worrying that I was leaving a spot open for the king to move into.

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  • $\begingroup$ Another secret is the double rook battery! $\endgroup$ – Rewan Demontay Apr 24 at 20:19
  • $\begingroup$ How does the queen have 6? I only can see two moves where it still protects the rook. $\endgroup$ – Rewan Demontay Apr 24 at 20:24
  • $\begingroup$ Only 2/6 squares that the queen can check the black king from, only 2 are checkmate-d3 and f5. This means that there is only 35 mates in one here. If I am missing something here, please do tell. $\endgroup$ – Rewan Demontay Apr 24 at 20:40
  • $\begingroup$ @RewanDemontay You are correct. I have an e4 rook problem. $\endgroup$ – Joel Rondeau Apr 24 at 21:21
  • $\begingroup$ It a nice try and idea, however. Perhaps you could try a different idea that uses two rook batteries. $\endgroup$ – Rewan Demontay Apr 24 at 21:23

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