square your knight needs, and it isn't pinned. Perhaps you nevertheless can get rid of it. Sometimes the guardian of the forking square may be captured: you can take it, and the piece that recaptures yours no longer will pro- tect against the fork.
Dg014: The position of Black’s king and rook make the idea for White clear enough: Nf7+. But f7 is protected by Black’s knight. Ask if it can be captured, and see that it can be―with
White’s rook. After playing RxN, White loses the rook to f6xR; but he regains it with the fork Nf7+, capturing Black’s rook next move and leaving White a knight to the good.
Dg014: White to move
Remember when you play a capture that your opponent may not be required to recapture. Usually that will be his choice, but in princi- ple he also may be able to make some other capture or counterthreat of his own. Here Black can reply to White’s RxN by playing RxN himself. Doesn't this end the forking threat? It does, but at a prohibitive price; for then White has Re8#—a classic back rank mate that takes advantage of the way Black's king is stuck in the corner. At the outset of the position the Black rook on d8 is the only piece protecting against this mating threat, so it can't afford to leave its post. We will study back rank mates in detail at various points later in this project (they get a section to themselves toward the end).
Dg015: White to move
Dg015: Again one of White’s knights is pretty far advanced up the board on f5; any knight planted on the fourth or fifth rank is a con- stant forking threat. So White does a quick scan for forks and observes that the knight is on a light square along with Black’s king and queen―which can be forked with Ne7+. The needed square is protected by one piece: the bishop on d6, but White can take out the bishop with his rook now on d1. So White picks up a piece, and if Black recaptures White can follow up with the fork: 1. RxB, c7xR; 2. Ne7+.
Dg016: White to move
Dg016: The thought process is identical: White examines his knight’s moves, or per- haps does a color scan and notices that his knight and Black’s king and queen all are on dark squares; one way or another there is a potential fork in Nd7+. The hindrance is that the bishop at c8 protects the needed square. Can White capture the bishop? Yes, with his queen—a sacrifice worth making for the fork that follows. So White picks up a piece, and if Black recaptures White can follow up with the fork: 1. RxB, c7xR; 2. Ne7+.
Dg017: White to move
Dg017: Your most advanced knight is on a light square, as are Black’s king and queen; there is a potential fork at e7. Ask if the square is safe, and see that it is guarded by the bishop at d6. Now look for pieces you can use to attack the bishop and notice the queen at d1―but also the knight at c4. It is important to notice both. The question is not “do you have a piece attacking X?” It’s “how many of your pieces—plural—attack X?” You don't want to sacrifice your queen when a knight will do, especially as it would make the se- quence a wash, Correct is 1. NxB; c7xN; 2. Ne7+.
Dg018: White to move
Dg018: The pattern repeats. White can fork three Black pieces with Ne6+. The only diffi- culty is the pawn at f7 that guards the needed square. There are various things one can do about such problems. The most obvious is simply to capture the pawn if you can, so here it goes 1. Rxf7, RxR, and now the pawn has been replaced by a piece that can't protect the e6 square. True, White sacrificed a rook to the cause; but now Ne6+ wins the queen. And then after Black recaptures RxN, White picks up a pawn that has been left loose by the se- quence: Qxg6. White ends up trading a knight and a rook for a queen and two pawns. You might imagine that the g6 pawn could be protected by Black's king, which (on this the- ory) would have escaped the knight fork by moving to f6. But if Black does move his king there, White mates in three moves. It starts with Nc3-d5+. Black has no good replies; if he plays BxNd5, for example, White has Rf1+. This forces Black to play KxNe6. Now White replies e4xBd5#.
When you capture the f7 pawn at the begin- ning, you should not assume that your oppo- nent necessarily has to recapture the way you would like. He might prefer to let the pawn go rather than play into your hands; it depends on the quality of his alternatives. Here Black has the option of replying to Rxf7+ with Kg8, which loses the pawn but also takes the king out of forking range. What happens next? Imagine the board with White’s rook on f7 and Black’s king on g8, and you should see that White then has an easy capture of a piece with RxN: the rook has protection from the knight on g5, and so cannot be recaptured by Black’s king.
Dg019: White to move
Dg019: The usual color scan reveals a poten- tial knight fork to be had at d6, but the square is protected. How many times? Twice—by the bishop at f8 and the knight at f7; be sure to account for all the guards, not just the first you notice. Fortunately White has bishops attacking each of the two bothersome pieces, but there still is a complication: when White’s bishops take Black’s bishop and knight, Black will use his king to recapture, and the king is supposed to be one of the pieces in the fork. Will its recaptures ruin the forking opportu- nity? Not necessarily; so long as the king ends up on f7 it still can be forked. But this means that it is important to perform the exchange on f7 last so that the king ends its travels there. Thus 1. BxB, KxB; 2. BxN, KxB; and now Nd6 forks king and rook and so wins the latter.
Naturally Black might prefer to bow out of this sequence earlier, giving up a piece rather than stepping into the fork. That's often how
tactics work, as we will see many times (but won't always point out): the victim can escape final execution of the fork or other idea, but only by making a sacrifice. In that case— which is normal—the tactic still must be counted a success.
The point to take away from this example, apart from the importance of accounting for multiple defenders, is that the order of opera- tions in a tactical sequence can matter a great deal. Here the tactic doesn't work if White takes Black’s knight first and his bishop sec- ond. When you consider a sequence that in- volves more than one exchange, ask whether changes in the order of the moves would make a difference to the outcome.
Dg020: White to move
Dg020: Black’s queen is about to take yours for free. Your initial impulse might be to re- treat your queen or play QxQ. Maybe one of those moves is right, but don't play either until you have asked whether they can be fit into an offensive plan. White’s most advanced knight is on a dark square; so are Black’s king and one of his rooks, suggesting a fork at f7. Be- fore you do anything you ask whether the needed square is protected, and how many times. Again, twice—by Black's bishop and queen. Unless you can eliminate both defend- ers of f7, no fork. Each of the defenders is attacked once: the Black bishop by your rook at d1, and the Black queen by your queen. The natural thought is to try QxQ, which you were considering anyway for defensive pur- poses, and then to notice that Black’s recap- ture, BxQ, leaves the forking square f7 loose for your knight. Capturing one of the two guardians in the right order thus takes them
both out of commission. And it gets better still: once Black's bishop on d5 is out of the way, White's rook on d1 attacks the Black rook on d8. So when White plays the fork, as he now can, he can use his knight to take the d8 rook without fear of recapture by the Black rook on e7.
Dg021: Black to move
Dg021: By moving to e2 Black’s knight would fork White’s king and queen. But the needed square is under protection—twice, from White’s knight and rook. Each of the guardians is attacked only by Black’s queen. So imagine taking out one of them, and then imagine taking out the other. If QxN, then White replies f2xQ (or BxQ) and the White rook at e4 still guards the needed square. But if Black begins with QxR, then White replies NxQ and now e2 is available for Black’s knight. Once more, an exchange of one of the two guardians effectively gets rid of both of them, as guardian #2 has to recapture the piece that captured guardian #1.
2.1.5. Distracting the Guard.