Figure[White to move]

The current principle in a diagonal rather than vertical setting, just for the sake of pattern reinforcement. Black’s knight and king on the same diagonal should jump out at you; what also should jump out are the White pawns that will be able to attack the knight once it is pinned. White starts with 1. Bb3; Black backs up the knight with c7-c6, which prevents it from being taken by White's bishop; so White plays 2. e3-e4, and the knight is lost.