28.Rac1 Rxc3 29.Rxc3 Rb1 30.Qf3
When a piece is dominated by the opponent’s pieces, one should first ask: how can I take it? Here the d1-knight is completely trapped, but it is not obvious how Black could attack it twice.
But the solution is much simpler, thanks to the theme of defence elimination. If the white queen weren’t there, the knight would be lost. So Black coolly offered a queen exchange with
30…Qf6!
31.Qxf6 (31.Qe2 is not better, because another defence elimination wins immediately: 31…Rxd1 32.Qxd1 Qxf2+ 33.Kh3 Qh2#) 31…Nxf6 wins the knight, and the game, with careful play.
Locked-in Piece/Square Clearance
Botvinnik,Mikhail
Stepanov,G
Leningrad ch-city 1930
1.d4 Nf6 2.c4 e6 3.Nc3 d5 4.Nf3 c6 5.Bg5 Nbd7 6.e3 Be7 7.Bd3 h6 8.Bh4 0-0 9.0-0 a6 10.a4 dxc4 11.Bxc4 Nd5 12.Bg3 N7f6 13.Qc2 Bd7 14.e4 Nb4 15.Qe2 Qa5 16.Ne5 Rad8 17.f4 Bc8 18.f5 exf5
The simple act of noticing that an important piece could be trapped is enough to induce us to imagine any tactical idea. Here, Black’s queen has no retreat to d8 because of the rook, and b6 or c7 are not always available. The game was virtually over after just one move, the electric
19.Bxf7+!
This is a combination on the theme of square clearance. White simply thought, ‘if my knight was on c4, the queen would be lost’. And lost it was.
19…Rxf7 20.Nc4
Everything is clear, though Black played on a little. Most of the players who continue such a hopeless game have a secret motivation: to avoid the doubtful ‘honour’ of being part, on the receiving end, of a miniature (that is, a game of less than 22 moves).
20…b6 21.Nxa5 bxa5 22.exf5 Rxd4 23.Be5 Rd3 24.Rad1 Bc5+ 25.Kh1 Rxd1 26.Qxd1 Nfd5 27.Nxd5 Nxd5 28.Qc1 Bf8 29.Bd4 c5 30.Bxc5 Rc7 31.Bxf8 Rxd 32.Rxc1 Bxf5 33.Bd6 Be4 34.Bc7
1-0
Sometimes it is not even necessary to take the imprisoned piece:
Piece out of play
Efimenko,Zahar
Sebenik,Matej
Porto Carras Ech-tt 2011 (1.4)
1.e4 c5 2.Nf3 Nc6 3.Nc3 e5 4.Bc4 Be7 5.Bf1 Bf8 6.Bc4 Be7 7.d3 d6 8.h3 Nf6 9.0-0 0-0 10.a3 a6 11.Ba2 Be6 12.Nd5 Nd4 13.Ne3 Nd7 14.c3 Nxf3+ 15.Qxf3 Bxa2 16.Rxa2 Bg5 17.Ra1 Nf6 18.a4 Re8 19.a5 Bxe3 20.Bxe3 Qd7 21.c4 Qc7 22.b4 Nd7 23.Rfb1 Nf8 24.Qd1 Rad8 25.Qb3 Rd7 26.Rb2 Ne6 27.Rab1 Qc8 28.Qa4 Ree7 29.b5 Nc7 30.f4 f6 31.f5 g5 32.Qd1
Black has a very difficult game, perhaps impossible to save in the long term. Basically, his pieces have no space, and it is difficult to imagine how they could obtain an attacking role for the moment; for instance, the knight is particularly difficult to activate.
Nevertheless, he chose a very strange way to play the position, by allowing his opponent to lock up the beast forever.
32…Qe8 33.b6!Na8
Now White is virtually a piece up, and in the old Capablancan fashion, he decides to attack on the side where the locked piece is not:
34.h4! h6 35.g4 Rh7 36.Qa4 Qd8 37.Rh2 Rdg7 38.Kf2 Qe7 39.Rbh1 Kf8 40.Kf3 Kg8
And now for the Alekhine touch: the Russian champion had demonstrated that in the case of an open file, the attacker should place his rooks in front, and behind them the queen, for maximum efficiency.
41.Rh3 Qd8 42.R1h2 Qe7 43.Qd1 Qd7 44.Qh1
1-0
Very elegant, and that was enough for Black.
White would have won as follows: 44…Rf7 45.hxg5 hxg5 46.Rxh7 Rxh7 47.Rxh7 Qxh7 48.Qxh7+ Kxh7.
White to play and win:
49.d4! exd4 (49…cxd4 50.Bd2 – 51.Bb4 – 52.Bxd6) 50.Bf2 – 51.Bg3 – 52.Bxd6 etc.
Trapped Piece
Carlsen,Magnus
Vallejo Pons,Francisco
Sao Paulo/Bilbao 2011 (8)
1.d4 d5 2.c4 c6 3.Nf3 Nf6 4.e3 Bf5 5.Nc3 e6 6.Nh4 Be4 7.f3 Bg6 8.Qb3 Qb6 9.Nxg6 hxg6 10.Bd2 Bd6 11.h3 Nbd7 12.0-0-0 Qxb3 13.axb3 a6 14.Kc2 Nh5 15.Bd3 Ng3 16.Rhe1 0-0-0 17.e4 dxe4 18.fxe4 c5 19.d5 Rde8 20.Na2 exd5 21.exd5 Nf5 22.b4 Nd4+ 23.Kb1 Nb3 24.Bc3 cxb4 25.Nxb4 Be5 26.Na2 Bxc3 27.Nxc3 Ndc5 28.Rxe8+ Rxe8 29.Bc2 Re3 30.Ka2 Na5 31.Rd4 Rg3 32.Ne4 Rxg2
32…Nxe4 33.Bxe4 Nb3 would have given Black an equal ending, for example 34.Rd1 Re3 35.Bc2 Nc5 36.b4 Ne4 37.Bxe4 Rxe4 should be a draw.
Here White noticed the unfortunate position of both black knights, and demonstrated with his next move a very neat way of taking advantage of this.
33.Rd2! Rxd2 34.Nxd2
And we can witness how one of the knights is lost. The threat of the fork on b4 wins the a5-knight, because this piece is trapped.
34…b5 35.b4 Nab7 36.bxc5 Nxc5 37.Ne4 Nb7 38.c5 f5 39.c6 fxe4 40.cxb7+ Kxb7 41.Bxe4 Kc7 42.Kb3 a5 43.Kc3 a4 44.Bc2 g5 45.Kd4 Kd6 46.Bd1
1-0
Trapped Queen
Kurnosov,Jgor
Varga,Zoltan
Austria Bundesliga 2010/11 (8.1)
1.d4 d5 2.c4 c6 3.Nf3 Nf6 4.e3 g6 5.Nc3 Bg7 6.Be2 0-0 7.0-0 Bg4 8.cxd5 cxd5 9.Qb3 b6 10.h3 Bxf3 11.Bxf3 e6 12.Bd2 Nc6 13.Qa4 Na5 14.b3 a6 15.Ne2 Nb7 16.Rfc1 Re8 17.Nf4 Bf8 18.Bb4 Nd6 19.Nd3 a5 20.Bxd6 Bxd6 21.Rc6 Re7 22.Qb5 Rb8 23.Rac1 Rc7 24.Rxc7 Bxc7 25.a4 Bd6 26.g3 Kg7 27.Kg2 Ne8 28.Be2
Black noticed that the white queen lacked breathing space, only c6 being available at the moment, and the knight might attack her from d6 or c7. He found a brilliant shot:
28…Ba3! 29.Ra1
On 29.Rc6 Nc7 forces 30.Rxc7 Qxc7 with a simple win for Black, who will invade on the c-file with the rook. On 29.Rc2 Nd6 30.Qc6 Rc8 the skewer wins the rook, which means game over.
29…Nd6 30.Qa6 Ra8
The queen is finally trapped.
31.Qxa8 Qxa8 32.Rxa3 Qc6 33.Ra2 Qc3 34.Rb2 Nc4 35.bxc4 dxc4 36.Rxb6 cxd3 37.Bf3 Qc2 38.d5 d2 39.dxe6 d1Q 40.Bxd1 Qxd1 41.e7 Qxa4 42.Ra6 Qe4+43.Kh2a4
44.Ra7 g5 45.Rd7 Qe6 46.Ra7 Qc6 47.f4 gxf4 48.exf4 Qe8 49.g4 f6 50.Kg3 Kf7 51.Kh4 Qb5 52.f5 Qb3
0-1
Let’s finish our chapter with a curious study.
It is not difficult, as long as the reader is able to grasp the saving idea, which is closely related to our theme.
Self-stalemate
Nordlohne,G
study 1911
In order to save himself, White has to find an original idea. The white king is unable to catch Black’s a-pawn, while his pawns cannot promote before Black’s passed pawn. Nevertheless, White has an amazing way to draw the game. Can you imagine what it is?
1.f4
1.h4? gxh4 2.f4 (2.g5 Kc7 3.f4 Kd7) 2…Kc7 3.f5gxf5 4.g5 Kd7;
1…KC7
Black has to approach the enemy pawns, because if 1…a5 2.h4!. Now White threatens h4-h5, so Black has to push on in order to queen first. 2…a4 3.h5 gxh5
4.fxg5! a3 5.g6 a2 6.g7 a1Q 7.g8Q+ with two pawns up and a winning queen ending.
1…Kc8 is the same.
2.fxg5 a5
3.Kg3!
White ‘traps’ himself in this strange-looking cocoon, and thanks to this self-dominati on achieves a draw.
3…a4 4.Kh4 a3 5.g3 a2
Stalemate!
Exercises
Exercise 1 Signal 5
*
Romanov,Evgeny
Clery,Nicolas
Cappelle la Grande 2012(1)
1.c4 e6 2.g3 d5 3.Bg2 dxc4 4.Qa4+ c6 5.Qxc4 b5 6.Qc2 Bb7 7.Nc3 a6 Ra4 Nd7 9.d3 Ngf6 10.Nf3 Be7 11.0-0 0-0 12.e4 Qb6 13.e5 Nd5 14.Nxd5 cxd5 15.Be3 Bc5 16.a5 Qa7 17.d4 Be7 18.Ng5 g6 19.Qd3 Rfc8 20.h4 Nf8 21.h5 Bc6 22.Qd1 Be8 23.Qg4 Qd7 24.Nf3 Rc2 25.Bg5 Qd8 26.Bh6 Rac8 27.hxg6 hxg6 28.Rfb1 b4 29.Bf1 Bb5 30.Bxb5 axb5 31.Kg2 Re2
(Solution on page 152)
Exercise 2 Signal 5
*
Safarli,Eltaj
Korobov,Anton
Baku 2012 (5)
1.e4 c5 2.Nf3 Nc6 3.Bb5 e6 4.0-0 Nge7 5.Nc3 a6 6.Bxc6 Nxc6 7.d4 cxd4 8.Nxd4 d6 9.Re1 Be7 10.Nxc6 bxc6 11.Qg4 Kf8 12.b3 Qa5 13.Bb2 e5 14.Qe2 Be6 15.Na4 f6 16.c4 Kf7 17.Bc3 Qc7 18.Qh5+ g6 19.Qh6 g5 20.Rad1
(Solution on page 153)
Exercise 3 Signal 5
**
Onischuk, Vladimir
Dvoirys,Semen
St Petersburg 2011 (S)
1.e4 c5 2.Nf3 d6 3.d4 cxd4 4.Nxd4 Nf6 5.Nc3 a6 6.Be2 e5 7.Nb3 Be7 8.Bg5 Be6 9.Bxf6 Bxf6 10.Qd3 Nc6 11.0-0-0 Nd4 12.Nxd4 exd4 13.Nd5 Bxd5 14.exd5 0-0 15.Qf3 Re8 16.Bd3 Re5 17.Kb1 Qa5 18.g4 Qxd5 19.Qxd5 Rxd5 20.f4g6
(Solution on page 153)
Exercise 4 Signal 5
**
Szabo,Krisztian
Lysyj,Igor
Cappelle la Grande 2012 (5)
1.e4 e5 2.Nf3 Nc6 3.Bb5 Nf6 4.0-0 Nxe4 5.Re1 Nd6 6.Nxe5 Nxe5 7.Rxe5+ Be7 8.Bf1 0-0 9.d4 Bf6 10.Re1 Re8 11.c3 Rxe1 12.Qxe1 Qe8 13.Qxe8+ Nxe8 14.Bf4 d5 15.Bd3 c6 16.Nd2 g6 17.Re1 Ng7 18.Be5 Bxe5 19.Rxe5 Kf8 20.f3 Bf5 21.Bf1 f6 22.Re1 g5 23.Kf2 h6 24.g3 Kf7 25.Be2 Ne6 26.Nf1 Bg6 27.Rd1 f5 28.Bd3 f4 29.Bxg6+ Kxg6 30.g4 Kf6 31.Nd2 b6 32.Nb3 Rd8 33.Nc1 c5 34.Ne2 c4 35.Rh1 h5 36.gxh5 Rh8 37.h4 Rxh5 38.hxg5+ Kg6 39.Rxh5 Kxh5 40.g6 Kxg6 41.Ng1 Ng5 42.Kg2 Kf5 43.Nh3 Nf7 44.Kf2 b5 45.a3 a5 46.Ke2 Nd8 47.Ke1 Ne6 48.Ke2 b4 49.axb4 axb4 50.Ke1 b3 51.Ng1 Kg5 52.Kf2 Nc7 53.Ke1 Nb5 54.Kd2 Nd6 55.Nh3+ Kf5 56.Ke1 Nf7 57.Ng1 Ng5 58.Kf2 Ne6 59.Ke1 Kg6 60.Kf1 Kh5 61.Kg2 Kh4 62.Ne2 Kg5 63.Kf2 Nf8 64.Ng1 Ng6 65.Ne2 Ne7 66.Ng1 Kg6 67.Nh3 Kf5 68.Ng1 Nc6 69.Ke1 Na7 70.Kd2 Nb5 71.Nh3 Nd6 72.Ke1 Ne8 73.Ng1 Nf6 74.Nh3 Nh5 75.Kf2 Ng7 76.Ke1 Ne6 77.Ng1 Kg6 78.Kf1 Kf6 79.Ke1 Kf5 80.Kf1 Nf8 81.Ke1 Nd7 82.Nh3 Nf6 83.Ke2 Ne8 84.Ke1 Nd6 85.Ng1 Nb5 86.Kd2 Nc7 87.Ke1 Kg5 88.Nh3+Kh4
89.Nxf4 Kg3 90.Nh5+ Kxf3 91.Nf6 Ke3 92.Kd1 Kd3 93.Ng4 Ne6 94.Nf2+ Ke3 95.Ng4+ Kf3 96.Ne5+ Ke4 97.Ke2 Nf4+ 98.Kd1 Ke3 99.Ng4+ Kf3 100.Ne5+ Ke4 101.Ke1 Ke3 102.Ng4+ Kd3 103.Kd1 Ne6 104.Nf2+ Ke3 105.Ng4+ Kf3 106.Ne5+ Kf4 107.Kd2 Nc7 108.Ng6+ Ke4 109.Ne5 Na8 110.Nd7 Kf4 111.Ke2 Nc7 112.Kd2 Ne8 113.Ke2 Kf5 114.Ke3 Nd6 115.Nb6 Ke6 116.Kd2 Ne4+ 117.Kc1 Nf6 118.Na4
(Solution on page 153)
Exercise 5 Signal 5
**
Onischuk,Alexander
Morozevich,Alexaiider
Sochi tt 2008 (6)
1.d4 Nf6 2.c4 e6 3.Nf3 d5 4.Nc3 Bb4 5.cxd5 exd5 6.Bg5 c5 7.e3 Nbd7 8.Bd3 Qa5 9.Qc2 c4 10.Bf5 0-0 11.0-0 Re8 12.Nd2 g6 13.Bh3 Kg7 14.Bh4 Nb6 15.Bxc8 Raxc8 16.Bxf6+ Kxf6 17.a3 Bxc3 18.bxc3 Na4 19.Rac1 Kg7 20.e4 dxe4 21.Nxe4 Rc6 22.f3 Nb6 23.Qb2 Re7 24.Nc5 Nd5 25.Nxb7
(Solution on page 154)
Exercise 6 Signal 5
***
Fressinet,Laurent
Brunner,Nicolas
France tt 2011 (4.4)
1.d4 d5 2.c4 c6 3.Nc3 Nf6 4.e3 e6 5.Nf3 Nbd7 6.Bd3 dxc4 7.Bxc4 b5 8.Bd3 Bd6 9.Bd2 Bb7 10.Rc1 Rc8 11.Ng5 a5 12.Qf3 Ba8 13.0-0 Be7 14.Qh3 b4 15.Na4 c5
(Solution on page 154)
Chapter 13
Crucial Defender/Overloaded Defender
This motif is perhaps the most important source of combinations. One player is attacked, he has to defend urgently against some danger, so he uses one of his pieces as a defender, whose duty will be to prevent certain threats.
This important defensive piece can become subject to various combinational themes:
- elimination of the defence;
- deflection
These are the two basic themes, but nearly every theme can be used: decoy, line/square clearance and line/square closing, pin, skewer, domination, double attack…
Deflection
Romanishin,Oleg
Werner,Clemens
Vlissingen HZ Open 2001 (8)
1.d4 d6 2.g3 Nf6 3.Nf3 Nbd7 4.Bg2 e5 5.c4 c6 6.Nc3 e4 7.Nh4 d5 8.0-0 Nb6 9.c5 Nc4 10.b3 Na5 11.f3 exf3 12.exf3 Be7 13.Re1 0-0 14.Qd3 g6 15.Bg5 b6 16.Na4 Rb8 17.Re2 Qd7 18.Rae1 Bd8 19.Bh6 Re8 20.Rxe8+ Nxe8
This is a very basic example, though the tactical sequence may not seem so easy. The queen on d7 has the important duty to defend the knight on e8 – without this protection, if the rook takes the knight it is checkmate. So White can sacrifice anything in order to deflect the queen from her defensive duty. The first move is not difficult:
21.Bh3!f5
Clearly forced.
Now White does well to insist on the trick with
22.Nxf5!
1-0
22…gxf5 23.Bxf5 Qf7 (23…Qxf5 loses the queen after 24.Rxe8+ Kf7 25.Rf8+)
In this position, another deflection wins on the spot. White must finish the game with 24.Bxh7+! Kh8 25.Bg6+−, winning the queen because 26.Rxe8 on the next move will be checkmate.
Black can’t resist with 24…Qxh7 because he loses both queen and king after the forced sequence 25.Rxe8+ Kf7 26.Rf8+ Ke6 27.Qxh7 with unavoidable checkmate, for example 27…bxc5 28.Qf7+ Kd6 29.Bf4#.
Deflection
Bauer,Christian
Kortchnoi,Viktor
Enghien les Bains 2003 (8)
1.Nf3 d5 2.d4 Nf6 3.c4 e6 4.g3 Bb4+ 5.Bd2 Be7 6.Bg2 0-0 7.0-0 c6 8.Qc2 Nbd7 9.Rd1 b6 10.Bf4 Bb7 11.Nc3 dxc4 12.Nd2 Nd5 13.Nxc4 Nxf4 14.gxf4 g6 15.Rac1 Rc8 16.e3 Nf6 17.a3 Nd5 18.b4 a5 19.bxa5 bxa5 20.Qb3 Ba6 21.Ne5 Qd6 22.Ra1 Rb8 23.Qc2 Rfc8 24.Ne4 Qc7 25.Rdc1 Bb5 26.Nc5 Bxc5 27.Qxc5 a4 28.f5 gxf5 29.Bxd5 exd5 30.Kh1 f6 31.Rg1+ Kh8
Here again, the black queen fulfills a crucial function: to prevent checkmate on f7 by the white knight. White has an elementary win thanks to a deflective move, which pours oil into the fire by adding another mating threat. With
32.Qd6!
White wins on the spot, because the queen is taboo, and mate on f6 is threatened.
32…Rf8
This loses the queen. After 32…Rb7 33.Qxf6+ Black loses everything: 33…Qg7 34.Rxg7 Rxg7 35.Rg1 Rc7 36.Qf8+.
32…Qd8 is even worse because of the one-move checkmate 33.Nf7#.
33.Qxc7
1-0
Elimination/Mate
Hübner,Robert
Kulovana,Eva
Prague 2011 (8)
1.g3 d5 2.Bg2 Nf6 3.c4 c6 4.Nf3 Bg4 5.Ne5 Be6 6.cxd5 Bxd5 7.Nf3 c5 8.Nc3 Bc6 9.0-0 Nbd7 10.d3 e6 11.e4 e5 12.Nh4 g6 13.f4 Bg7 14.Be3 0-0 15.f5 Qe7 16.g4 Qd6 17.g5 Nh5 18.f6 Bh8
Black has allowed White to weave a mating net around his king, as well as one around the fianchettoed bishop, which is trapped permanently. Should a white piece give check, it would be mate right away.
Who better than the knight can achieve the desired attack in such a closed position? Immediately, we imagine the h4-knight going to f5, attacking the queen with a double mating threat on e7 and h6. At the moment, there is a defender: the g6-pawn. So naturally, we will go for the deflective – and definitive! –
19.Qxh5!
1-0
If Black takes with 19…gxh5, 20.Nf5 creates the double threat of checkmate on h6, and taking the queen. There is no satisfactory defence.
Deflection
Ernst,Sipke
Klein,David
Oslo 2011 (6.6)
1.d4 Nf6 2.c4 e6 3.Nf3 d5 4.Nc3 dxc4 5.e4 Bb4 6.Bg5 c5 7.Bxc4 cxd4 8.Nxd4 Bxc3+ 9.bxc3 Qa5 10.Bxf6 Qxc3+ 11.Kf1 gxf6 12.Rc1 Qa5 13.g3 Bd7 14.Kg2 Nc6 15.Nb5 Ne5 16.Qd6 Bxb5 17.Bxb5+ Qxb5 18.Rc7 Nd7
18…Ng6 was playable, when the position would be unclear.
White has to deflect Black’s queen. That’s an easy task:
19.Rb1
1-0
Resignation was not premature here, because if Black tries to keep an eye on the d7-knight with 19…Qa4 (19…Qxb1 allows 20.Qxd7+ and 21.Qxf7 checkmate) White has the complementary deflection with 20.Rb4, when either Black’s queen or his king is lost.
Deflection
Ni Hua
Polajzer,Danilo
Rogaska Slatina tt 2011 (3.3)
1.e4 c5 2.Nf3 e6 3.d4 cxd4 4.Nxd4 Nc6 5.Nc3 Qc7 6.Be3 a6 7.Qd2 Nf6 8.0-0-0 Bb4 9.f3 Ne7 10.Nde2 d5 11.Bg5 dxe4 12.Bxf6 gxf6 13.Qd4 exf3 14.Qxb4 fxe2 15.Bxe2 f5 16.Rd6 Nc6 17.Qf4 Qe7 18.Bf3 0-019.Rhd1 e5 20.Qh6 Be6
White has a large advantage here, thanks to his powerful attack against the damaged black fortress. Several moves are advantageous, but there is one that wins by force.
White’s most dangerous threat is to bring a knight to d5, attacking the black queen while threatening the decisive Nf6+ and Qxh7 mate. The defender of the d5-square is the e6-bishop, which also has the function of controlling a rook invasion on d7.
That is why the first player decided to play the deflecting move
21.Rd7!+− Qb4
After 21…Bxd7, 22.Nd5 wins queen or king: 22…Qe6 23.Nf6+ Kh8 24.Qxh
7#.
22.Nd5+−
22…Bxd5
This is now forced.
23.Qg5+ Kh8 24.Qf6+ Kg8 25.Bxd5
Now a possible defensive try was
25…Nd8
In the game Black resigned after 25…Qf4+ 26.Kb1. Now, 26…Nd8 is useless because of the forced 27.Rxd8 Raxd8 28.Bxf7+ Rxf7 29.Rxd8+ Rf8 30.Rxf8#.
After the text, the best way to win is the brutal
26.Rxd8! Raxd8 27.Bxf7+ Rxf7 28.Rxd8+ Rf8
And now follows a very fine triangula-ti on mano euvre:
29.Qe6+ Kh8
29…Kg7 30.Rd7+ and mate.
30.Qxe5+
Now White controls the e1-square.
30…Kg8
31.Rd3! f4 32.Rd7! Rf7 33.Qg5+ Kh8
Also, 33…Kf8 34.Rd8#.
34.Rd8++−
1-0
Deflecting the Main Defender
Bojkov,Dejan
Van Riemsdijk,Herman
Queenstown 2012 (7.5)
1.e4 e5 2.Nf3 Nc6 3.Bc4 Nf6 4.d3 Be7 5.0-0 0-0 6.Bb3 h6 7.Re1 Re8 8.Nbd2 Bf8 9.Nc4 b5 10.Ne3 Na5 11.Bd2 Nxb3 12.axb3 d5 13.exd5 Nxd5 14.Nxd5 Qxd5 15.Bc3 f6 16.Nh4 b4 17.Bd2 g5 18.Qh5 Bb7 19.Qg6+ Bg7 20.Ra5 Qc6
White has infiltrated the weakened light squares in the black king’s position. 21.Nf5 would be strong, if Black did not have checkmate on g2! So the queen should be challenged before we play the knight.
Tune Your Chess Tactics Antenna Page 10