The tactical device of removing the guard is also known as removing the defender. The name of the tactic is almost sufficient in itself to describe how it works.
The opponent has a piece which is defending another piece, or maybe a key square, and our plan is to remove that defender so that we can continue our attack on the other piece or square.
The game Maki – Tella, Tampere 1997 illustrates the concept. After 38.Kg2 (diagram below), the Black queen attacks the White rook on e4, which is defended only by the knight on c3.
Tella removed the defender with 38…Rxc3, after which Maki resigned. White could recapture with 39.bxc3, but 39…Qxe4 leaves White a piece down.
In Marovic – Piasetski, Toronto 1990, Black’s target after 24.Kf1 (diagram below) is not a piece directly, but the e4-square.
Black sees that, could he get rid of the defenders of that square (the knight on d2 and the queen on c2), he could fork White’s rooks and prevent White’s king from moving out of the way, so that the rooks can defend each other. But how to get rid of two defenders in one go?
24…Rxd2! Not only does this remove one of the defenders, the knight, but also the second defender, the queen. Seeing that 25.Qxd2 leads to 25…Qxe4 and the loss of a rook, White resigned.
Here is a more subtle variation on the theme, where the removal of a defender has to be prepared by first disabling the defender’s defender! After 36.Rxg7 in the game Nakamura – Beliavsky, Minneapolis 2005, the board was as below.
The White knight is defending the rook on g7, which is attacked by Black’s king. Although the knight is attacked by the Black queen, it feels safe in its protection by the White queen.
However, after 36…e4! White resigned, because the chain of protection crumbled. The knight’s protection by the queen is blocked by the e-pawn, which is defended by Black’s knight on c3, which means the White knight is hanging. No matter what White does, he cannot save both the knight and the rook.
Finally, an example from the King’s Gambit Declined opening. After the moves 1.e4 e5 2.f4 Bc5 3.Ne2 Qf6 4.c3 Nc6 5.g3 Nh6 6.Bg2 Ng4 7.Rf1 Nxh2, the board is as below.
White, not realising the importance of the f3-square (from which Black’s knight can deliver mate), or maybe thinking it was sufficiently protected by the bishop on g2 and the rook on f1, played 8.fxe5??. This gave Black the opportunity to remove both defenders of f3 in one go, as Piasetski did in his game.
After 8…Qxf1+ the rook is gone; and who doesn’t love a queen sacrifice? White is forced to take with the bishop and after 9.Bxf1 the bishop is gone, leaving f3 open for 9….Nf3#.