Montaje de la caja de engranajes

In the positions just seen, the attacking player used his rook to give check. The opponent’s need to defend against the check gave the piece that had been uncovered by the rook time to win material on the next move. Some-times the rook can achieve much the same effect by threatening mate, as this puts the enemy under pressure similar to that created by a check. A rook most commonly can threaten mate by offering to drop onto the back rank when the enemy king is trapped there. This theme is worth our independent attention for two reasons. First, seeing a mate threat often is harder than seeing a check; it takes some practice. Second, when you work with mate threats you have to be especially careful to consider what trouble your oppo-nent can make in reply. Since by assumption you haven't put him in check, you may have left him with latitude to respond with checks of his own that seize the initiative.

Dg367: In the current position White has the kernel of a discovered attack along the g1-a7 diagonal, where his rook masks his queen—

which otherwise would be able to take Black’s queen. Now think about execution:

what large threat can White create with the rook?

Dg367: White to move

Rxf6 is its only capture, but the move is more than that: it aims the rook at f8, where it would mate the trapped Black king with RxR#. So in reply to 1. Rxf6 Black has to capture White’s rook, which of course creates time for White to play QxQ on his next move.

Now notice that if it were Black’s turn to move he would have Qa1+. White would be forced to reply KxQ—after which Black has the knight fork NxB, winning a piece. This should worry you a little for the reason sketched a couple of paragraphs above. The first move in White’s planned sequence (Rxf6) is a capture and mate threat, but not a check; so you have to consider whether he can give checks of his own that will derail your plans. In this case Black could respond to Rxf6 with two consecutive checks, as just discussed: Qa1+, and then NxB+, forcing White to move his king. So are White's plans foiled? No; for then Black is out of checks that hold the initiative: the next move he wants to play is NxQ, but he can’t afford it because Black mates with RxR. White thus holds onto the queen.

Dg368: A similar idea. First find where White has the makings of a discovered attack. The kernel lies on the long a1-h8 diagonal, where White’s rook masks his queen in familiar fashion. Look for a target for the queen once it’s unmasked and see that Black’s queen is in the line of fire—and that it's loose.

Dg368: White to move

The challenge now is straightforward: vacate the rook from d4 in a way that compels a re-sponse from Black. The rook has no checks, so examine the Black king’s position for vul-nerabilities. It is trapped on the back rank;

although it isn’t entirely sealed in by its pawns, White’s bishop closes off the flight square on g7. The same idea we saw in the previous position thus works here. An attack by White’s rook against Black’s rook on e8 would be a mating threat, because if White can play RxR the game ends. White makes the threat with Re4. Black has to eliminate White’s rook to stay in the game. He has two ways to do it. The first is BxR, to which White replies QxQ and mates soon. Black also has the option of replying to Re4 with RxR. How should White reply?

This time the answer for White isn't quite QxQ, since Black then uses his rook to mate on e1. White instead needs to work with checks to prevent that possibility. By moving his rook off the back rank, Black has made this easy: White plays Qc8+, which requires Black to interpose his queen on d8. White takes it (QxQ+); then we go through the same process with Black's rook; then it's mate.

Black's best reply to 1. Re4 is probably 1.

...Qe5, which avoids the mate just shown but loses his queen and then his bishop.

Dg369: Another variation on the same idea, this time from Black’s side. Where does Black have the makings of a discovered at-tack?

Dg369: Black to move

On the long a8-h1 diagonal. As usual the rook masks the queen, and if it were moved Black could play QxQ. The important question in-volves what to do with the rook. Again it has no checks, so consider the White king and its vulnerabilities. Here as in the previous posi-tion it is stuck on the back rank, as Black’s bishop on h3 cuts off its escape. And once more the king has a single guard: the rook on e1. If Black threatens that rook with his own, he threatens mate. So he has two possibilities, either of which works: 1. …Rd1 or 1. …Re5.

There is a little more to say, because you al-ways must ask whether your opponent has a way to both move the targeted piece out of danger and spoil the mating threat. White's queen can't move to the east because Black then threatens to mate with Qg2. But in re-sponse to either of those rook moves we have sketched, White can play 2. Qxh3, avoiding QxQ and preparing to interpose the queen on f1 if Black plays RxR. But then he still loses the queen—and also both rooks. It goes 2.

…RxR+, 3. Qf1, RxQ+, 4. KxR, QxRh1+.

Black has a queen left and White has nothing.

Dg370: Black to move

Dg370: Observe the offensive tension on the board. Black would like to use his queen to take White’s rook on f5, but then he would lose his own rook to White’s queen. How to break the jam? By use of the queen-rook-queen alignment on the e1-a5 diagonal—the three-piece kernel of a discovery. White’s queen is ready to be taken if the rook can va-cate c3 with sufficient violence. The rook has no way to give check, but study White’s king:

it’s trapped on the back rank. If Black could land a rook there he might have a mate threat—except for the protection furnished by White’s rook on b1; if Black could take that rook with his own, he would indeed threaten mate. So the threat by Black of RxR is almost as good as a check, and Black can achieve this with 1. ...Rb3.

What next? White is confronted with multiple threats, so he might naturally look for a way to defuse them both—a square where his queen would be safe and would defend against RxR#. One possibility is 2. Qc1. This takes care of those two problems, but not a third one: Black now can play QxR with no worries, because White’s queen no longer is in position to retaliate by taking the rook on c3. (But before playing QxR Black has to exchange rooks on b1; otherwise White meets Black’s QxR with c2xR.) White is left with a queen against Black’s bishop and queen. A better reply idea for White would be 2.

a2xRb3. Black then plays QxQ next move, so this time White has lost a queen for a rook;

but at least he ends up with two rooks against Black’s queen and bishop.

Dg371: Black to move

Dg371: First note the kernel of a discovered attack spread along the long h1-a8 diagonal.

If unmasked, the Black bishop could take White’s queen. Can the rook be vacated from f3 with check? Yes; Black can play Rf1+, and White would have to reply RxR (his queen would then be pinned). Then Black could play BxQ, to which White replies KxB, and Black has won a queen for a bishop and a rook.

Don't settle for this, though; think through all of your options. How else could the rook va-cate f3, and with what results? He could threaten mate with RxN, looking to play RxR# next move. RxN therefore has about the same effect as a check but picks up a knight along the way. Now what would White do?

Stay aware of every piece bearing on the en-emy king’s position. Here Black has a second rook he can involve, this one on the open e-file. So if White replies to RxN with RxRd3, Black plays his other rook to e1—and it’s mate. White instead needs to create a flight square for his king, and therefore replies to RxN with QxB. It avoids checkmate but loses the queen. The key thing for Black now is not to play the tempting RxQa8, but to instead use RxR+. It wins a rook, and since it's a check it effectively is a free move; White has to spend his reply saving his king, and so can’t move his queen out of harm’s way on the eighth rank. When Black has finished giving checks and doing whatever damage he can in the process, White’s queen still will be on a8 for the taking.

Capturing the rook on d1 first with check, then taking Black’s queen later, is an example of using the priority of check—the principle that a check must be addressed before any other threat pending on the board. It is a valu-able idea that we will revisit often and study in detail later.

Dg372: By now the queen-and-rook kernel for Black on the long diagonal no doubt is obvious. Look for a target for the queen if unmasked, and see that White’s queen is loose and ready to be taken on c3.

Dg372: Black to move

Black just needs a threat to make with his rook on e5. The rook can’t directly threaten anything at the moment, but the key fact about the piece is that it is part of a battery of rooks aimed at White’s back rank. Play through the first rook capture in your mind’s eye: 1. ...RxR+, to which White replies 2.

RxR. Now what? The answer is tricky. Are you inclined to play 2. ...RxR+, checking the king? Not so fast: White’s queen protects e1, so White would be able to play 3. QxR, taking the queen out of danger and dissolving the check at the same time. Any other ideas?

Consider the surprising 2. ...Re2, which puts pressure on a square next to White’s king (f2) that Black already attacks with his queen.

This allows Black to threaten mate with 3.

...Qxf2; White must do something to prevent it. If he plays 3. QxQ, Black doesn't recapture right away with g7xQ; rather, he first plays RxR+, winning a rook and checking White’s king (the priority of check again). After the king moves to h2, then Black still has g7xQ—

and only Black’s rook is left on the board. If White instead plays something other than QxQ on the second move of the sequence, Black plays QxQ on his next move.

The hard part of this position is seeing the value of Re2 for Black. The key point to re-member is the sensitivity of squares next to the king, especially when they already are attacked by a queen. Adding another attacker against such squares, as Black does here with his second rook, can create a crushing threat even if no check or capture is made with the move.