Here is exercise 176 in Level 20 of CT-art. Black to move.
Although, I have seen this problem at least 30 times before, I just got it wrong on my last past. I see before me the classic conditions of anastasia mate. A Knight looking to make its way to d2 check, a queen ready to sac on a2 and a rook to get into the a file for a checkmate.
But I see an issue here the rook can take if the knight moves to d2 . Then I start calculating a bunch of other ideas which goes nowhere .
The structural consideration I do not see is that the rook only offer pseudo protection that moving the rook to capture allows blacks queen to check on the back rank. Rook returns is captured checkmate.
Pseudo Protection is something I do not always see especially when it is combined as in this case with another motif. I often do not calculate lines because I believe a pawn could capture but is absolutely pinned to the king.
I am trying to be vigilant about remembering I have this occasional tactical vision blindness and hope writing this post will help me remember.