Figure[White to move]

Breaking a Relative Pin: Moving the Screened Piece.

Breaking out of a relative pin is easier than breaking out from an absolute pin, of course, because there are many more options. The pinned piece legally can move, and sometimes the benefits of doing so may be great enough to offset the loss of the piece exposed to capture. And the screened piece, unlike the king, can move more than one square at a time, and so may be able to both end the pin and launch an attack of some sort that leaves no time for the formerly pinned piece to be taken. Here, as when we studied ways of breaking absolute pins, the lessons are important for those occasions when you may find yourself the victim of such a tactic and need a way out; but it also is important to understand them so you will know when a pin you are contemplating will succeed. We will start with a series of positions where a relative pin may (or may not!) be broken by moving the screened piece.

In this first example White doesn't attack anything much. But what can White attack on his next move, and what patterns do you see in Black’s position? Notice Black’s knight and queen lined up on the same diagonal, and realize White can play Bb5, pinning the knight. Would the move result in any gains? If you just consider the forces that each side can bring to bear on the pinned piece, it might seem promising: White next will be able to play his queen to a4 so that he has two pieces trained on the knight, whereas Black has nothing to use in defending it except his queen.

There is, however, another question to ask: could Black interrupt White’s sequence by moving one of the two pieces out of the pin? Normally Black wouldn’t dare move his queen, because while it is causing the knight to be pinned it also is the only thing preventing the knight from being captured. One exception we will see later is when the screened piece—here, the queen—can leave its square with a threat; another exception, and the saving option in this case, arises when the screened piece can move out of the pin while still protecting the pinned piece. Thus after White’s Bb5 Black looks for another square for his queen from which it can guard the knight; he finds a8 and moves his queen there. The pin is dissolved and the knight still is protected, so now if White tries to gang up on the knight with Qa4 Black can simply move it to safety.