Today's game, from a match in Monaco between the two leading Dutch grandmasters, features a curious optical illusion. In the diagram position, Black has just played 40...Be7 attacking the white queen. White's reply was 41.d8=Q! when 41...Bxd8 loses to 42.Qxf8+ while 41...Bxd6 allows 42.Qxg5. It is rare enough for a bishop to be pinned along a diagonal; in this case we see a bishop pinned simultaneously along both its diagonals!

The entire game was a fine example of the combative nature of the King's Indian Defence, and how to cope with it. When the modern King's Indian was worked out in the 1940s by Soviet grandmasters such as Boleslavsky and Bronstein, they won countless games with an almost automatic attacking plan once White had closed the centre with d5. Black just gets his knight out of the way from f6, then plays f5, f4, g5, g4, switches the rook over from f8 to f6 and h6, or f7 and g7, brings the queen to h4 or g5, and slaughters the white king, trapped in its castle on the corner.

Meanwhile, White would usually advance on the Q-side, but Black always had the inherent advantage that his attack had a king at the end of it. Gradually, however, White's resources improved as ways were found to speed up the Q-side advance then, having secured clear advantages on that wing, to invade - usually down the c-file - and eat a way through to the black king before Black's own attack broke through.

And that is a fair summary of what happened in this game. White's 19.Qc2 is an interesting idea, showing that he views the execution of c5 as more important than regaining the a-pawn, but even after White's attack had made good inroads, he still needed to stay remarkably cool in defence as Black kept finding more ways to rekindle his ambitions.

White's 25.g3! was an important move, slowing down the Black attack just enough. At the end, White's attack won the exciting race by a short head.

White: Loek van Wely

Black: Jeroen Piket

King's Indian Defence

1 d4 Nf6 24 dxe6 Rg7

2 c4 g6 25 g3 Qf6

3 Nc3 Bg7 26 c5 Kh8

4 e4 d6 27 Bc4 Nf8

5 Nf3 0-0 28 Qb3 Bg5

6 Be2 e5 29 c6 h5

7 0-0 Nc6 30 Rd7 Nxd7

8 d5 Ne7 31 cxd7 Rf8

9 b4 a5 32 Rf1 fxg3

10 Ba3 axb4 33 hxg3 h4

11 Bxb4 Nd7 34 Nxc7 Rh7

12 a4 Bh6 35 Qc3 Qh6

13 a5 f5 36 Kg2 hxg3

14 Bd3 Rf7 37 Qxe5+ Bf6

15 Qb3 g5 38 Qxg3 Qg5

16 Rfd1 g4 39 Ne8 Rh3

17 Nd2 b6 40 Qd6 Be7

18 Nb5 bxa5 41 d8=Q g3

19 Qc2 Nc5 42 Qd4+ Kh7

20 Bxc5 dxc5 43 Qxe7+ Qxe7

21 Nb3 f4 44 Qd7 Rh2+

22 Nxc5 Ng6 45 Kxg3 resigns

23 Ne6 Bxe6