Here is another more advanced application of our current principles. The germ of the idea is on the c-file; when you see pieces lined up like this, thoughts of a pin should not be far behind. You see that Black’s queen is loose and lies behind his knight. White’s queen on c2 is aimed through both of them, though White’s knight is in the way on c3. The point: you would have a pin if your own knight could be cleared out of the way in a fashion that required a time-consuming reply by Black. If there were some simple capture White’s c3 knight could make that would call for a recapture by Black elsewhere on the board, the solution would be simple: play that exchange, then go after Black’s newly-pinned knight with the pawn thrust b2-b4. The difficulty is that White’s knight has no such obvious harm to inflict. An opportunity must be created for it.

You might think through the situation backwards in the following way. The most plausible square White’s knight can reach with the potential to make a threat is e4; on that post it is safe and could threaten f6, and also would add an attacker against the c5 knight that is the target of these operations. The problem with the threat to f6 is that Black has a knight there that can strike back against the knight White is thinking about using for this operation. So maybe White can force a replacement of Black’s f6 knight by capturing it: BxN, met with BxB. Yes, that leaves a loose piece on f6; so now if White moves his c3 knight to e4, he has a threat against the bishop on f6 that requires a response from Black. If Black’s response is Bd8, protecting his queen, you play NxN, taking his knight, which now is attacked twice and protected only once. If Black instead replies to Ne4 by moving his bishop to e7, the knight is defended twice—but now it is pinned, because the queen behind it remains loose, so White can throw the pawn at it with b2-b4 and win the knight with b4xN a move later.

To summarize, White plays 1. BxN, BxB (performing an exchange on f6 to leave behind a loose Black piece that White can attack with his knight); 2. Ne4 (attacking Black’s loose piece, clearing his knight off of the c-file, and leaving behind a pin on Black’s c5 knight while also making a second attack on it). Now White has threats against enough enemy targets that he will win a piece no matter what Black does.