Clearing Needed Lines

Dg320: Black to move

If the bishop were vacated from the d-file, the rook would be directed at White’s bishop, which is guarded. Once you clearly under-stand these obstacles, ideas for getting rid of them at the same time suggest themselves:

move the Black knight out of the bishop’s way, and in the process use it to capture the unsuitable target on d3 and cause it to be re-placed by something better. Thus NxB, and now if White wants to avoid the loss of the piece he has to recapture QxN. Now both problems have been solved. The Black bishop’s path to h2 is open, and Black’s rook has a good target in the queen on d3.

Dg321: White to move

Dg321: Where does White have the makings of a discovered attack? On the c-file. But once more only the queen-behind-bishop kernel is there; the queen lacks a good target, and the bishop has no checks to give, although it can attack Black’s queen with Bxe6. So again

think about what it would take to make the tactic work. (a) First, the pawn on c7 would need to be replaced by a better target. So con-sider taking the bad target with one of your other pieces (like the White knight on b5), and ask whether your opponent would have to recapture with a more valuable piece. (b) Second, it would help to have a better target for the unmasking bishop to threaten—

preferably Black’s king, which unlike its queen would not be able to move and cause trouble when attacked. Black’s king is behind its queen, but the queen protects the same pawn on c7 that we are trying to trade for a better target. The solution to the problems at both ends becomes obvious: White plays Nxc7; if Black recaptures QxN, White has a check for his bishop with Bxe6 and a target for his queen in the loose Black queen on c7.

The lesson repeats: be clear about what obsta-cles prevent your idea from working; often two problems can be solved with a single stroke.

3.1.7 Clearing Needed Lines.

In the last two positions the discovered attack required a preliminary exchange that both improved the target the unmasked piece would attack and opened a line for the un-masking piece to use to make a threat against the enemy king. We now look more closely at this last principle: identifying lines that need to be opened to make a discovery work, and clearing them with exchanges and threats.

Dg322: White to move

Dg322: In the diagram position, start the stan-dard identification of the kernel discovery.

Here it's on the d-file, where White's rook is aimed at Black’s queen at the other end of the board. The difficulty—both in seeing the ker-nel and in perfecting it—is that White has two bishops in the way. If one of the bishops could be cleared from the file in a manner that is time-consuming for Black, the board might be set up for an effective discovery by the bishop that remains. Each bishop has a possi-ble threat (try imagining the board with one of them removed, then the other): the d3 bishop can go to c4 and threaten Black’s rook on a2, and the d4 bishop can capture Black’s knight on f6 and threaten to take another piece from there. So first White plays Bc4, requiring Black to respond by moving the rook to a8 or perhaps a5; and now the way is clear for White's other bishop to play BxN. Black has to spend his reply move saving his queen (this is one of those discoveries where the threat by the unmasked piece is greater than the threat by the unmasking piece).

Notice that after White plays BxN, Black could try to take the offensive by playing his e7 bishop to c5—a move that seems to expose his queen to capture, but actually is quite safe because it gives check (when White played BxN, he created an open diagonal to his own king). Now if White moves his king, Black can play QxBf6; in other words, the Black bishop's move to c5 was another discovered attack. But White has an answer: he can block the check and save his piece by simply re-treating his bishop to d4, having already won a piece. We see again a recurring point: don’t forget to look for checks you opponent might be able to throw into the middle of the go. Black could respond to the initial move 1.

Bc4 by moving his queen to a8 to protect his enemy piece as part of a double threat, realize that he might be able to reply by adding to its protection as well as by moving it. If he does add to its protection, imagine going ahead with the capture and permitting him to recap-ture, and ask how the board would then look.

Obviously this practice would be just as im-portant if you were playing the Black pieces here; else you might lose your queen.

Finally, let’s return to the initial diagram to emphasize the most basic point of the posi-tion: if you see the skeleton of a discovered attack but with extra pieces in the way, think about how you might clear the obstructions in a forcing manner that cuts down your oppo-nent’s choice of replies—i.e., with checks, captures, and threats. Here a simple one-move threat by the d3 bishop forced Black’s reply and made possible a classic discovered attack.

More broadly the position shows the impor-tance of seeing the kernel of a discovery even when there are other pieces also cluttering the line.

Dg323: White to move

Dg323: White’s bishop masks an attack up the d-file; this time the potential attacking piece is White’s queen. White’s bishop has an obvious place to go that will cost Black some time: Bxh7+. The problems are that Black’s queen—the natural target of the operations—

is guarded by a knight, and that the Black pawn on d4 blocks the d-file. Start with the second problem; examine how the pawn is threatened and defended. It is attacked by White’s c-pawn and two knights, and de-fended by a knight, a bishop, and a queen.

Play through the liquidation of those pieces in your mind’s eye and see what is left at the end: 1. c3xd4, Nxd4; 2. NxN, BxN; 3. NxB, QxN. With the board thus simplified, what would be possible? The c and d pawns would be gone; both of White’s knights would be gone; Black’s knight and bishop would be gone; and Black’s queen would be loose on d4, in front of White’s bishop—a classic setup for a discovered attack via Bxh7. After Black plays KxB, White plays QxQ, winning Black’s newly loosened queen.

This position looks a little complicated be-cause it involves several exchanges, but its structure is simple. Once you see the forma-tion for a discovered attack, you just methodi-cally work through all the exchanges bearing on the obstructions that prevent it from work-ing. This example illustrates a particularly useful version of the idea: when an enemy pawn blocks a discovered attack against a piece that lies behind it, perhaps the piece you want sooner or later can be made to replace the pawn if the pawn is taken. That is what happened here: the d4 square never was emp-tied; rather, the pawn eventually was replaced by the target of the exercise—the queen. But to get to any of this you first have to see the basic pattern for a discovery on the d-file without being blinded by the obstacles in the way.

Of course if Black sees all this coming he will simply forfeit the pawn at the beginning rather than head down the road toward larger losses by making a recapture; he will notice the kernel of a discovery for White and will realize that d4 is a square of danger.

This position is a good study in the value of playing through a series of liquidations in your mind's eye. The particular type of liqui-dation shown here is fairly common: a pawn near the middle of the board often will be protected and defended several times, making

it important to understand what would happen if all those potential captures and recaptures were played out.

Dg324: White has the makings of a discov-ered attack on the g-file, of course, where his rook and bishop are in the standard formation.

White looks for a violent, time-consuming move he can make with the g2 bishop and finds—nothing. BxB is met by QxB with no gain; Bf3 just loses the bishop.

Dg324: White to move

Still, a discovered attack pattern with a rook aimed at the enemy queen is an important opportunity, so White looks for other moves he could make that would create a target for the g2 bishop. It would be ideal if the bishop could check Black’s king. Where would it need to go to do that? To d5. What stands in the way? Black’s bishop at e4. That bishop cannot be captured, but it can be threatened with Qc2, Qd3, Qd4, or Qd5. Qd5+ is most interesting because it checks Black’s king and so requires immediate attention. Black would have to either move the king or take White’s queen. If he moves the king, White plays QxB (and if Black then plays QxQ, White has BxQ). So Black will play BxQ. Reconsider the board as it then would appear: the same potential for a discovered attack would exist, and now the White bishop’s path to d5 would not be blocked by Black’s bishop; Black’s bishop would be on d5. So White plays BxB+, and Black replies Kh8; and now White has RxQ. He has exchanged queens and won a bishop.

You might also have considered starting with Qd4. It looks safer because it doesn’t expose

your queen to capture by Black’s bishop, but still attacks the bishop a second time; and it creates the threat of mate with Qxg7. But Qd4 has the major disadvantage of not giving check. A key difference between giving check and creating a mate threat is that a mate threat doesn't force such a narrow range of replies on your opponent. He may be able to address it by giving a check of his own that seizes the initiative. In this case Black can respond to Qd4 with Rxa2+. White has to reply KxR—

and then comes another check from Black:

Ra8. Since White has nowhere safe to move his king, he has to interpose his queen on a7 and lose it next move to RxQ. Then White has the recapture BxR, but that wasn’t exactly what he had in mind at the outset. Remember:

if you resort to threats that don’t give check, you have to consider any checks (and any successions of checks) your opponent might be able to use to interrupt your plans.

Dg325: Black to move

Dg325: Where does Black have the makings of a discovered attack? Actually in two places: on the c-file and on the h-file, where his knight masks his queen. Since we are fo-cusing here on discoveries by bishops, start by working with the threat on the c-file. The rook on c8 is poised to take White’s queen if the bishop can be vacated from c5 in a force-ful enough way. But where can it go? The first thing to consider is whether the unmask-ing piece can give check. That’s not possible here, both because the king is on a light square and because the pawn on f2 blocks the bishop’s path to the back rank. But when you see an obstruction like the f2 pawn, ask what you could do if it were gone. If the pawn weren’t there, Black could play Bg1. Does

that qualify as interesting? It should, for then the position begins to look a lot like one we saw a few frames ago; the bishop would be attacking a square adjacent to White’s king at which his queen also would be aimed.

An idea thus emerges: if Black could get his queen aimed at h2 and get the f2 pawn out of the way, then Bg1 would threaten mate and be an effective discovered attack. The Black queen’s path is blocked by the Black knight on h5, but the knight can evacuate its square with check: NxB+. If White replies f2xN (the h-pawn can't be used because it's pinned), now Bg1 is possible and threatens both Qxh2# and RxQ.

By the way, notice that White can reply to Bg1 with Bc4, limiting his immediate losses to a piece. White’s queen then protects h2 against a mating attack, since the White pawn and piece on the second rank suddenly are both gone. After Black plays RxBc4, White slides the queen over to e2, where it is safe and still foils the mate threat.

In a later chapter we will study knight discov-eries like the one that unmasked the Black queen’s attack on h2, but already you can see how the train of thought might have started there just as easily: the knight in front of Black’s queen can move out of the way with check (NxB+). Black imagines the board as it would look after the recapture f2xN, and rec-ognizes the same sort of idea we saw earlier:

his bishop can unmask an attack against White’s queen, and at the same time add a second attack on the pawn in front of White’s king by moving to g1.

Dg326: White to move

Dg326: White's bishop and queen are charac-teristically arranged for a discovered attack, with Black’s loose queen making a fine target on d4. Everything is prepared except a good threat for the bishop to make when it vacates the d-file. It would like to give check, natu-rally, but its lines to the king from b5 and g6 are blocked. What to do? When your goal is to clear a line, consider attacking pieces that are guarded by the pieces you need to move.

Here the lines that White's bishop needs to give check are blocked by Black’s d7 bishop and f7 pawn. If White can capture something that one of those pieces protects, then the piece will have to move to recapture, a line will be cleared, and perhaps White can win Black’s queen with a discovery. As it hap-pens, both of Black's blockers protect the pawn on e6, and White can take it with Rxe6+. Now if Black recaptures by any means, he opens a diagonal leading to his king, and White has a discovery that does win the Black queen on the next move—either Bb5 or Bg6. Obviously Black can capture the bishop easily either way, but you don't care;

you just want to make him spend a turn that way so you can take his queen.

In practice, seeing all this just gives White a way to take a Black pawn for free (and im-prove his position a bit), since Black would of course rather lose the pawn of e6 than his queen; if he is attentive—and you should as-sume he will be—he will reply to the capture by moving his king to f8, not by recapturing and setting himself up for the discovery.

Many of the positions we are studying work that way. In practice they yield a payoff, but not necessarily the first and best one you say;

for your opponent may see the coming disas-ter and choose to make some lesser sacrifice to avoid it.

Dg327: Now consider how these ideas can look when you’re playing defense. The two sides are fighting for control of the center;

Black would like to get rid of one of White’s central pawns. He attacks the pawn on d4 twice (with his queen and knight), and it is defended just once (by White’s knight). So should he take it with Nxd4?

Dg327: Black to move

It is important to visualize such sequences and consider what would be possible on the board as it would look afterwards. Picture 1.

…Nxd4, 2. NxN; QxN. The implications of the resulting position are clear if you notice the kernel for a discovered attack that White has on the d-file all along. That kernel is rea-son for Black to act with great care in any operations on that file; taking the d-pawn is asking for trouble, because it creates a target for White’s queen after it is unmasked. In this case the bishop on d3 would end up able to give check with Bxb5, winning Black's queen on d4 next move. So Black dares not play Nxd4 in the first place after all.

Notice how those quick exchanges on d4 ended up leaving White with a new way to check Black's king and also with a great new target for his queen to take once it's un-masked. An earlier point repeats: when a con-tested pawn lies in the center, don't just ask who has more pressure against it. Ask what the board would look like after those pres-sures are spent.