Now combine the current theme with an earlier one. A routine color scan (or a look at your checks, or a look at your knight moves) turns up a potential fork of Black’s king (good) and knight (no good) to be had by playing Nxc6. Can the knight on b4 be exchanged for something better? And what about the fact that the forking square, c6, is guarded? Experiment with exchanges that may clarify the board. 1. Ra4xN leads to 1. …RxR; now the fork has a better target in the rook, but the forking square still is protected by the second Black rook at b6. So it becomes a straightforward problem of attracting away the guardian of the forking square by attacking a piece it protects. Just do another exchange: 2. RxR, RxR then allows Nxc6+.