2024/11/17 DPA: "Royal Interference"

White to move:

White would like to play Qc7# but the Black Queen guards that square.

1. Nc6 blocks the Queen's defense of c7 but it also opens up an attack on our Queen and 1. ... Qxe5 ends the threat.

But 1. Rc1 Qxc1  2. Nc6 now works since the Black Queen [and no other piece] can defend c7.

2. ... Qxc6 is the only way to avoid immediate checkmate but 3. bxc6 renews the threat.  3. ... Rd7 defends but 4. Rxd7 leads to 5. Qc7#.

No, that was wrong.  I missed something.

There is another way to interfere:  1. Nc4 Qxc4  2. Nc6 Nxc6  3. Qc7#.

And I see why 1. Rc1 doesn't work:  1. ... Qxc1  2. Nc6 Qh1#.  Ouch!

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The key was recognizing the checkmate on c7 and working backwards to figure out a way to remove the Queen defender.  The first Knight move gets the Queen off of the a1-h8 diagonal which then frees up the second Knight to block on c6 without exposing White's Queen to capture by the Black Queen, which would be the case if the Black Queen was still left on c3.

The other thing the Solver had to see was that 1. Rc1, while it accomplishes the same things as the solution, allows 2. ... Qh1#, which I completely ignored, as I was focused on the attack [and this was probably the intent of the creator].

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For those who question why 2. ... Nxc6, ask yourself how capturing with either the pawn or the Bishop would alter the outcome.  The point is that after the 2 sacs, c7 is undefended.  So it doesn't matter what Black does.

By the same token, Black had other options like 2. ... Qxg3+ and 2. ... Ng4+, which, while they delay checkmate, do not alter it.  So those are not reasons to think the puzzle is somehow "wrong".