Dg284: White to move
Dg284: What Black pieces are vulnerable to a pawn fork? His knight and bishop, of course.
What are the obstacles? The Black queen, which blocks the pawn’s path; and again the pawn will need protection if it is going to at-tack a bishop. The problems here are the same as in the previous problem, and so is the solu-tion: f2-f3 drives away the queen and also provides protection to support the fork e3-e4 that follows. (Note that after 1. f2-f3, Black has to move his queen somewhere; pay atten-tion to where it will go, as its opatten-tions are very limited. Black likely will play it to h4. Now White pauses to play the exchange 2. QxQ, g5xQ; he plays this first because his own queen is unprotected. Then he plays the fork in the middle of the board.)
Dg285: White to move
Dg285: By now the idea here should be easy to spot: Black’s rook and c7 knight are a square apart on the same rank, and White’s
pawn on d5 is a square away from being able to fork them. The problem is that d6 is occu-pied by an enemy pawn. How do we get rid of it? In familiar fashion: take something it pro-tects, forcing it to move to recapture. So White plays NxN; Black recaptures d6xN;
and now the fork d5-d6 wins Black’s other knight.
Dg286: White to move
Dg286: It is White’s turn four moves into the Four Knights opening. He is considering Bc4 to develop his pieces further. What happens if he plays that move? Picture it: his bishop and e4 pawn will be in the classic position to be forked by Black’s d-pawn, and Black would be able to replace the pawn on e4 with a suit-able target by playing Nxe4, inviting the reply NxN. Now White’s knight and bishop would be forkable with d7-d5. True, White could then take Black’s pawn with his bishop (Bxd5), but then Black plays QxB. When the smoke clears, Black will have won no mate-rial but will have a better position: a pawn in the center and both bishops ready to move.
The point of the position is not the precise outcome, though; it is the importance of hesi-tating before leaving one of your pieces one square away from any of your own pieces or pawns on the same rank. Consider whether your opponent could start an exchange that would create a working pawn fork at the end.
2.5.3. Forcing Pieces into Place with Threats and Checks.
So far we've dealt with cases where your op-ponent began with two men ready to be for-ked by a pawn. One of them may have been an unsuitable target—e.g.,an enemy pawn that
needed to be upgraded with an exchange — but the basic geometric motif already was present. These next positions differ because the geometry for a pawn fork needs to be cre-ated; enemy pieces have to be forced onto squares where they can then be forked. How do you force a piece onto the empty square where you want it to go? Sometimes a threat will do the trick. Normally your opponent will move a threatened piece someplace safe, but if it has a limited range of motion because some of its escape squares are blocked or at-tacked, a threat may force it where you want it to go. Consider this section a general set of lessons in paying careful attention to where threatened pieces will move.
Dg287: White to move
Dg287: In this first example White has a pawn that can jump into position to attack the Black queen with g2-g4. The threat is of lim-ited interest by itself, but it would make a terrific first half of a double attack: if Black’s king could be goaded onto f5, White would have a pawn fork. Of course White's knight is there now, and Black's king will want to avoid capturing it precisely because of the fork that then results. But whether these thoughts occur to you or not, on principle you would want to examine every check White can give and its consequences. White has a check at d4 with his knight that achieves nothing. He has checks with the queen at d7 and f7 that lose the queen right away, but another check at e7 where the queen enjoys protection from the knight. How would Black respond? He would have to move the king with KxN. White imagines the board as it would then look and realizes that Black's king and queen would then be forkable with g2-g4.
A loose end remains. When we went over White's checks, we left one out: Re1. It looks good; indeed, it forces the same initial result as Qe7: Black has to play KxN, and now White has that same pawn fork. But there is a grave difference in what follows from there.
After White plays g2-g4, Black naturally moves his king away with Kxf4, and then White has g4xQ (the execution of the fork)—
but now notice the state of the g-file. White's pawn no longer is there; the only things left behind are White's king and queen: a perfect chance for a pin by Black, which he exploits with Rg8. White can't move his queen, and will lose it next move. White's better starting move, Qe7, avoids this calamity by getting the queen off the g-file right away.
The general lesson of this last variation is to be careful to study all of your checks. Some-times one looks as good as the next for a pur-pose on first inspection, but turns out to have quite different side effects. The more specific lesson is to be alert to one particular type of side effect: lines that get opened by a tactical sequence, such as the g-file in this case. This last possibility may seem startling and worri-some if you haven't studied pins; but once you get through that part of this project, you will know that the sight of White's queen and king on the same line is something to notice from the beginning here.
Dg288: Black to move
Dg288: Look for patterns in the layout of White’s pieces or for threats you can make;
the result either way should be to see Black's potential pawn fork d4-d3. The problem is that once the pawn arrives on the forking square it would be attacked twice — by
White’s queen and rook—and protected only once, by Black’s rook at d8. So the pawn gets taken if it steps forward. Yes, but let that se-quence play out in your mind’s eye: 1. …d3;
2. Rxd3, RxR; 3. QxR, and now what would be possible on the resulting board? White’s queen and knight would be arranged for the fork e5-e4, winning the knight at f3. In effect the initial fork was just another threat that drew the White rook, then (after an exchange) the White queen, into position for a different fork.
Incidentally, note the importance of Black playing the exchange RxR, QxR before exe-cuting the fork at the end. If Black plays the pawn fork against White’s rook and knight after the rook has moved to d3, White breaks out of it with RxR+. Once the rook has been replaced with White’s queen, however, White has no good way to break out of the fork. The general points are (a) to always ask whether you can improve the target of a double attack with another exchange, and (b) to always con-sider what your opponent’s best reply to the fork would be; he may have a check or threat that would enable him to break it—especially if his king is not one of the parties to the fork.
Dg289: White to move
Dg289: Sometimes a threat by one pawn will force an enemy piece into position to be forked by another. The previous position was one example; here is another that works a bit differently. White sees that Black’s bishop has limited opportunities for escape, as the knight on c5 cuts off its main line to the rear.
(A bishop with so little room to retreat is a vulnerability you want to spot in your oppo-nent's position and avoid in your own.) So
White gets interested in threats he can make against the bishop and their consequences, and looks at a2-a3. Study the bishop’s flight squares and you see that if it moves any deeper into White’s territory it gets taken, so it has to move instead to a5. Now Black’s bishop and knight would be a square apart on the same rank, so b2-b4 would fork them; the pawn on a3 gives the b4 pawn the protection it needs to be able to attack the bishop.
The general lesson: keep an eye out for en-emy pieces that are hemmed in by their own pieces or by the edge of the board; often they have few options if they are attacked, making the consequences of the resulting sequence easy to predict and sometimes making a tactic easy to execute.
Dg290: White to move
Dg290: The same idea. Again observe that that Black’s bishop has limited motion (look behind it; it can’t retreat toward a7). So White considers threatening it with b2-b4. Here as before, Black’s bishop gets taken if it tries to escape by moving farther into White’s terri-tory. Instead Black might play Bd6—putting the bishop one square away from the knight on the same rank. Now White forks the two pieces with e4-e5, with cover for the pawn supplied by the bishop at f4. (Or Black replies to b2-b4 with the suicide run Bxf2; after White replies KxB, Black has Nxe4+, and White ends up winning a piece for two pawns.)
Dg291: This time White's bishop on b5 is the piece with a limited ability to retreat. When you see a piece trapped in this way, think about threats against it. For Black that means
considering Rd5 here. The bishop then gets taken if it moves to e2, d3, c6, d7, e8, or a6.
Its only safe move—and it's only temporarily safe—is Bc4. (If White tries Be8, Black plays Kf8 and now the White bishop is attacked twice and defended once with nowhere good to go. Remember that Black's rook would be on d5....) What then would be possible?
Dg291: Black to move
White’s queen and bishop would be set up for the pawn fork b7-b5, with Black’s rook at b2 furnishing the cover.
Dg292: White to move
Dg292: No Black pieces are poised to be forked. But again it is good practice to exam-ine the consequences of threats you can make by advancing your pawns. White has just one such threat to consider: d4-d5. The Black knight would flee, but don’t stop with that observation; ask where it would go. It has only one safe square: c7. Re-evaluate the board as it then would look and notice that Black’s knights now would be a square apart on the same rank. (Alternatively, after push-ing forward a pawn to threaten somethpush-ing, you can always ask what would happen if you
simply pushed it again.) So d5-d6 then wins a knight, with the bishop on g3 providing nec-essary protection against Qxd6.
That is the idea, anyway. Against an alert player the outcome would be favorable but not quite so simple. As usual you need to con-sider whether he might seize the offensive.
Here Black’s best reply to d4-d5 is not to move his knight to c7; it is to play Ne7xd5.
Then when White plays e4xN, Black has the recapture Qxd5. White still gains a piece for two pawns, but Black has reduced his losses nicely. There is a valuable defensive lesson in this for occasions when you find yourself the target of an unavoidable fork. If you are des-tined to lose a piece, you might as well do whatever damage you can with it (or with another piece you can sacrifice in its place). A doomed piece that has this odd sudden liberty to go on a suicide mission is known not as a kamikaze but as a desperado.
Dg293: Black to move
Dg293: The drill: look at any threats you can make with your pawns and ask what conse-quences would follow. It is especially impor-tant to consider this when the threatened piece has little room for escape. Here Black has the simple g7-g6, putting pressure on the queen.
The queen’s freedom of movement is limited;
it has to move to h4. Now what? Well, Black can attack it again: g6-g5, and now White is in a jam. To see why, consider his king; for it is affected by these movements of your g-pawn, which now seals off f4 and h4, and also protects those squares if you want to occupy them yourself. So look for your next check find Bxf4—mate.
This means that after Black's second push of the g-pawn, White wouldn't want to play Qh5.
He would need to try f4xg5. Too bad about that f4 pawn of White's. But put this together with the earlier point about f4—its vulnerabil-ity to Black's bishop—and a new idea comes to mind: if the pawn at f4 first could be re-placed with the White king, Black could fork White's king and queen by putting his pawn on g5. So Black reconsiders that check we mentioned: Bxf4, which he plays early: before or after White’s queen has retreated (naturally you could have found the whole idea here by starting with the check Bxf4). Whether White plays KxB or moves his king to h4, Black’s marching g-pawn then wins the queen.
A similar result can be reached by skipping Bxf4+ at the beginning and just playing 1.
…g7-g6; 2. Qh4, g6-g5; 3. f4xg5—and now 3. … Bxg5 attacks and wins the queen. The bishop has protection against capture, and if White tries to move the queen to safety on h5, Black has f5-f4. This forces Kh2, which in turn allows Black to play Rh1#.
Dg294: Black to move
Dg294: This time White’s queen is the piece that is cramped: it’s up against the side of the board with little room to retreat. Black con-siders a threat against it with g6-g5. Where will the queen go? It gets captured if it moves to h5 or to anywhere on the fourth rank (look and see). So it has to move to h3. Yet now its relationship with the knight on f3 calls for a pawn fork: g5-g4 wins the knight, with Black’s own knight at f6 supplying the needed protection for the pawn.
In the game this position came from, between Tal and Botvinnik, it was White’s turn to move. Tal played Nc3-d5. Now if Black plays g6-g5, White plays NxNf6+. Since this checks the king, Black can’t play g5xQ; he has to capture White’s knight. After that ex-change gets rid of the knight on f6, White’s queen has plenty of flight squares and the fire is out. But of course the first important point in all this is for White to recognize that he is in danger. The tipoff is the immobility of his queen.