Localización básica de problemas

covered attack has been to find the kernel of it and build from there. But what if the kernel doesn't yet exist? Then a bit more imagination is required: you need to experiment with moves — here, moves by bishops and the pieces they can mask—that create kernels; you learn to notice when a move or exchange you might make will bring the kernel of a discovery into existence. Here are some illu- strations.

Dg357: White to move

Dg357: In the study White sees that he has a rook on the open e-file. He has a bishop that can reach the same file with Be7, masking the rook. Look at the position of the bishop and rook here; see how they thus are one move away from being in the classic formation for a discovery. The question is whether the move that creates the kernel also forces a target into place. Here the bishop’s move to e7 would threaten Black’s rook on f8. Black’s reply would be forced and thus easy to foresee: the rook would have to move to e8. This little sequence would create a working discovered attack: a masked piece, a masking piece, and a target all along the e-file. Now the bishop just needs a good place to go next. Bb4 threatens Black’s queen; if the queen defends itself in any way, White plays RxR#. So the queen must be lost. Notice how easy this posi- tion would be if it started with the kernel in- tact (i.e., with 1. Be7, Re8 already played). The challenge is just to think of White mov- ing his bishop in front of his rook and to care- fully consider the result.

Dg358: Black to move

Dg358: Black faces the threat of mate with RxR, so if he’s going to take the offensive elsewhere he will need to work with checks that force White to play defense. The checks he can give with his queen—Qxh2, Qf1, or moves to the g-file—don’t quite work; but how about 1. …Bxh2+? White’s only legal reply is 2. Kh1, retreating into the corner. But now the full kernel of a discovered check has been completed: Black’s queen is behind his bishop and aimed at White’s king. This al- most enables a mating sequence with 2. …Bg3+ 3. Kg1, Qh2+ 3. Kf1, Qxf2#. That last move won’t succeed here because of White’s knight on d1, however, so Black needs something else for his bishop to do as it clears the h-file and discovers check. It can’t attack anything; it’s on a dark square and all of White’s pieces are all on light squares. But consider whether it usefully might block any lines. With 2. …Be5, Black severs the protec- tion White’s queen had provided to the rook on e8. Again White must move his king to g1; and now Black plays RxR.

Dg359: White to move

Dg359: Start by examining every check. White has two: Rh8, which loses the rook

without a good follow-up, and Bh7, which checks the king and (since the bishop is pro- tected against capture) requires the king to retreat to h8. And now—aha!—we have the kernel of a discovered check: White’s bishop masks the path of his rook toward Black’s king. So where should he move the bishop? It has no good Black targets on light squares, but the more important possibility to consider is that the bishop might help finish Black's king. The best piece to involve as a help to- ward that end is his queen. White would mate if it could be placed on h7; and what keeps it from being placed there is the presence of White’s own bishop on the needed diagonal. So we remove the bishop from the line with 2. Bg8+. Black has to move his king out of check with KxB or Bh6; either way, White has Qh7#. (The queen takes protection either from the rook on h1 or the bishop on g8, de- pending where Black's king moved.)

Dg360: Black to move

Dg360: Now a defensive use of our current idea, and in a horizontal setting. Black is ahead a piece. He has to address the threat against his knight now made by White’s king. How? With offense: Black has a bishop on the eighth rank and can move his queen be- hind it with Qd8. That move creates the ker- nel of a discovered attack against White's queen. To make the threat really interesting the bishop would need somewhere good to go. Can it reach White’s king? Not quite; it can move to a6, though, at which point it is aimed at—the threatened knight. Now the defensive idea comes together: if Black plays Qd8 and White then plays KxN, as he now threatens to do, Black would be able to win the queen with Ba6+. Odd as it may seem, by

moving his queen to d8 Black thus defends his knight on e2: he creates a discovered at- tack that will be unleashed if his knight is taken.

Dg361: Black to move

Dg361: Again White’s king can take Black’s knight on e2. Black has a bigger problem, too, for White threatens to mate by playing Qf7+, forcing Black’s king to h8 and then mating on f8 (his queen goes there and gets taken by Black’s rook; then White has RxR#). Yet Black can address both problems with the in- genious Qe8. See what this does: now Black’s queen is on the e-file, ready to defend the knight once his bishop on e5 has moved out of the way. In other words, the kernel of a discovery has been created expressly to pro- tect a fellow piece at the other end of it. In- deed, this does better than protect the knight and defend f7 against mate. It means that if White plays KxN, Black then has a discove- red check with Bb8+, attacking White’s queen as well as his king.

We aren’t finished; don't forget to consider what White would do about the check you are imagining when Black moves his bishop out of the way. White could interpose his rook with Re3, not only blocking the check but attacking Black’s queen. So then what? Black looks for another check that would then be possible; so long as he keeps White busy with checks, the capture BxQ will still be waiting for him afterwards. Here Black’s next check is Qb5+. White again can interpose the rook, but this time it only blocks the check; it can pose no threat against a queen attacking along a diagonal. Now it's safe for Black’s bishop to take White’s queen.

Dg362: White to move

Dg362: You might start this one by observing that White's f5 bishop can give check with Bx h7. By itself this doesn't achieve anything, but it's something to know as you think through your options. Okay, now look at your other forcing moves — your possible captures — and what they do. There is 1. NxN, inviting Black to retake with QxN. The interesting thing about this exchange is that it puts Black's queen on a line with the White bishop, which we know can give check.

Maybe now you begin thinking about slipping White's queen onto h5 to create the structure of a discovered attack on the fifth rank; you wonder how you might do it in a violent man- ner that forces Black's reply and keeps the discovery intact. Or maybe you just keep looking for other captures you can make. Ei- ther way you come to inspect 2. Bxg7. Black has to reply BxB or else lose the rook on f8. But after Black plays BxB the way is clear for White to play 3. Qh5, threatening mate with Qxh7. The mate threat is easy for Black to defang, of course, with h7-h6, but it serves its purpose: White gets his queen onto line with his bishop and with Black's queen, and Black has had no time to fend off the discovered attack that now has been set up on the fifth rank. White pulls the trigger with 4. Bh7+, requiring Black to play KxB and unmasking 5. QxQ. White wins Black’s queen and pawn in return for his two bishops.