Sometimes it isn't feasible to capture or overwork an enemy piece that impedes your plans. There remain other ways to get rid of such a piece, one of which is to threaten it and thus force it to move. When we speak of “attacking” the guard, this is what we mean: not capturing it, but aiming a piece at it with the threat of a capture. This technique tends to work best when the guardian is a king or queen, since their high value typically gives them no choice but to flee an attack and thus abandon their defensive duties; just beefing up their protection is not an option. But lesser pieces also may find it necessary to flee a threat if they're loose or worth less than the piece that threatens them. Or in other cases the attacked piece may not flee; instead it may capture your attacker, and this may be much to your liking—indeed, it may be your intention—if it means something else has been left loose in the meantime.
Getting rid of a guard by attacking it can be complicated, and the hard positions in this section are among the most demanding in the book. The reason is that when you attack a piece other than the king you are not forcing your opponent’s reply in the same way you do by making a capture or check. You have taken nothing from him, so he may have plenty of reply options to consider: a counterthreat, a check, or a move of the attacked piece that takes it out of danger and still enables it to perform guard duty. These possibilities all have to be considered when you make a threat, but sometimes they can be cut down by using threats that have other good things going for them as well—for example, threats that also give check or fork another piece.
We will start with attacks on the king when it guards one of its pieces, since these are the easiest to understand and use. Then we will look at the more difficult problem of chasing away a queen that guards a piece or mating square. Later we will consider attacks on lesser pieces.