The Bg3 Trick

The Bg3 trick is a tactic that is not well known, but is fairly simple to set up. Below is an example:

The bishop is temporarily immune to capture when it moves to g3 since black has to deal with the threat of mate on h7. While black has defended against the mate, the knight can now move to f3 to fork the king and queen. Rxf3 is forced since the king has no square to move to, and Bxf3 follows. This is a simple tactic to set up as the attacker just needs a bishop and knight attack the h2 square, and a queen behind the bishop.

Try it out in the puzzle below: