|Diagram 1. White to move|
1.Nxd6 seems to be the obvious move. However, the immediate recapture of the rook isn't very advantageous. We have a few forcing moves up our sleeve. We can postpone the recapture for a while, and retake under better, decisive conditions. Right now, we contain the black king in a box existing of 3 squares: g8, f8 en f7. When the knight recaptures, it covers the invasion square f7. To let the knight and queen work together, we must try to bring the queen in contact with f7, with tempo.
In order to recapture, the queen must stay in contact with d6. On e7, the queen can do both: staying in contact with the invasion square f7, where the knight and the queen converge, and stay in contact with d6, which is necessary for the recapture. And the white queen can get there with tempo via 1.Qe8+ Kg7 2.Qe7+.
Now there are two boxes the black king can choose from.
|Box 1. White to move|
|Box 2. White to move|
And here the reasoning stalls. The invasion square has guided my attention via the invasion square. But how to prevent T&E (Trial and Error) mode from here?