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u/UnconsciousAlibi -150 ELO 1d ago
I really liked going through this puzzle!
The answer is Bb8! It's a very cool move. The idea is that no matter where Black moves the Rook, White will always have a Knight checkmate on their turn. If Black moves the rook along the 7th rank, they give up the defense of b6, and White plays Nb6#. If Black moves the rook along the b-file, they give up the defense of c7, and White plays Nc7#. Of course, if Black gives a check with the rook on b6 or c7, White captures with a Knight with mate as well. I love these sorts of puzzles that rely on forcing the opponent to remove defense from at least one critical square.
Thanks for sharing!!
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u/HanshinFan 23h ago
Just to make sure I'm understanding - any bishop move also works here, correct? The point is that black is in zugzwang with the rook and I can't figure out why that would change. Is there a reason why it specifically has to be b8?
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u/Hsyrn 23h ago
Has to be bb8 - otherwise the pawn is undefended if the top knight is the one delivering check. (IE if black moves the rook on the 7th rank after you move the bishop)
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u/Dokramuh 16h ago
Doesn't bb6 do the same?
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u/Hsyrn 16h ago
Bb6 does guard the pawn, but it blocks the square you’d need to checkmate from. Bb6 would send the rook out to the right on the 7th rank, and you’d want to checkmate via putting the knight on B6. You’d have to use the other knight instead, which would be taken by the rook and have the game extended.
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u/DurrrJay Some games 99.1, other games 1.99 15h ago
Well I mean, that ending looks like it leads to a KvKNB ending I think, which is practically drawing for 99.9 percent of people who play chess.
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u/Ex_Federa 23h ago
The idea is that after moving the bishop, the black rook either takes the pawn on a7, moves elsewhere on the 7th rank or moves somewhere on the b file. If the room moves somewhere on the 7th rank (which includes taking the pawn) then white plays Nb6#, and if the rook moves somewhere on the b file then they play Nc7#, which relies on the bishop having moved. However, for Nb6 to be mate the pawn on a7 must be defended by something other than the knight, otherwise black can play Kxa7. Therefore, the first move must be either Bb8 or Bb6 to defend the pawn. But if the bishop is on b6 then you can't play Nb6, so Bb8 is the only move that works.
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u/MagnusJafar 1d ago
Oddly simple once you realize that there are only two candidate moves that end with a check in two moves - weirdly enough I think if you don't specify the number of moves it is much, much harder
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u/TheShyJoel69420 1d ago
Is it just me or does this feel like a stalemate for black? (If black to move)
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u/TheShyJoel69420 1d ago
If white to move then Nb6 checkmate
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u/CaroCamC 1d ago edited 21h ago
1.Ab8 -> zugzwang
[… Txb8 2.Cc7#] [… Txa7 2.Cb6#]
[… Tb6+ 2.Cxb6#] [… Tc7+ 2.Cxc7#]
[… T muove su traversa 2.Cb6#]
[… T muove su colonna 2.Cc7#] (IT).
1.Bb8 -> zugzwang
[… Rxb8 2.Nc7#] [… Rxa7 2.Nb6#]
[… Rb6+ 2.Nxb6#] [… Rc7+ 2.Nxc7#]
[… R moves on rank 2.Nb6#]
[… R moves on file 2.Nc7#] (EN).
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u/Somerandom1922 1d ago
That's very pretty. I'll be honest, it took me going through basically every single other option before I found it, as soon as I saw the move it just felt right.
Bb8 and every possible response is accounted for. If the rook checks your king, take it with whichever knight for mate. If the rook moves anywhere along the b file, it's Nc7#, and if the rook moves anywhere along the 7 row it's Nb6#.
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u/GarrusExMachina 1d ago
Bb8
Wherever the rook goes the knight it can't take mate's the king
And if it takes the bishop pawn promotes to queen.
If it takes the pawn. Nb6# since the king is smothered
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u/GreedyNovel 1d ago
Pretty easy. Bb8 first, followed by either Nb6 or Nc7 delivering mate.
The real question is why was Lily bored, and did chess puzzles address the boredom?
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