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2025/09/26 DPA: "Back Rank Checkmate Sans Pawns"

2025/09/26 DPA: "Back Rank Checkmate Sans Pawns"

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White to move:

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At first glance, it looks like the classic Smothered mate but it's not, since White cannot check on the a2-g8 diagonal.

Or can't he?  1. Qf7+ Rxf7. 2. Rxb8+ Rf8 and there's no follow-up.

1. Qxf8+ Kxf8. 2. Rxb8+ Ke7. 3. Bc5+ Ke6. 4. Re8+ Kd5...

Moving the Knight uncovers the Bishop's attack on g7, making Qxg7# a threat.

1. Ng6 Qxe7

1. Qxf8+ Kxf8. 2. Bc5+ d6. 3. Bxd6+ Ke8. 4. Rxb8#.

Or 3. ... Kg8. 4. Rxb8+ Qe8. 5. Rxe8#.

[Edit:  4. ... Qe8 is impossible since the Knight is blocking the Queen.  I missed this while visualizing the solution.]

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There were several plausible ideas [Smothered mate, back rank mate, attacking g7, etc] so the key for me was working through them to find the flaws.

Then, the Solver had to not only see the Queen sac but that immediately capturing the Knight allowed the King to escape to e7, which should lead one to consider the Bishop check [but I didn't make that conclusion immediately].

1. Qxf8+ forces the King to f8.

2. Bc5+:  this critical Intermezzo ["in-between move"] cuts off the e7 escape.  If the Solver plays 2. Rxb8+ immediately, the King escapes.

[Edit: I just noticed this uncovers the Rook's attack on the Queen but it's clear that checkmate is in the air so the Solver needs to ignore the "free" Queen [which, if taken, will cost the Solver the game, since he had to sac his Queen for a Rook in order to initiate the sequence and he started the puzzle down a Rook]].

3. Bxd6+ continues the attack.  Notice that whether the pawn blocks or not doesn't change anything because the Bishop is safe on either c5 or d6 and the Knight controls d7 so the fact that the pawn isn't there anymore, which might have allowed escape, doesn't matter.

4. Rb8#.


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This is tricky to visualize:  the Knight covers the light squares d7 and f7 while the Bishop covers the dark square e7.

In effect, this is like a simple back rank mate that we're more familiar with:  here, the Black pawns block the d7, e7, and f7 escape squares just like the White Bishop and Knight do in the puzzle.