1. Nf3 c5 2. g3 Nc6 3. Bg2 g6 4.
Petrosian's own system against the KIA involved 7... d6!
8. e5! 
To control critical dark squares at f6 and d6.
8... d6
P. H. Clarke writes of this move: "Correctly played.
This must come sooner or later, and to put it off in favor of
8... b6!?
or 8... Qc7 would alow
White more time to prepare for it."
Ron Henley notes that without this break in the center, Black
would present White with a simple plan to control the dark squares by Nbd2,
Nc4, Be3, Qd2, and Bh6 etc. Consider the following sample line that could easily
arise if Black simply developed "naturally": 8... b6 9. Nbd2 Bb7 10. Nc4 Nf5 11. g4! Nh4 12. Nxh4 Qxh4 13. g5! 
9... Nf5
10. Nbd2
White threatens 11.Ne4 Qd5 12.c4! and the Queen must either abandon the c-pawn or risk further attack after 12... Qf5 13.h3!
10... Qc7
10... b6!? seems risky because it opens the long diagonal, but Henley suggests this may have been best.
11... b6 12. Bf4 Qd8 13. Ne5 Bb7 14. Nc4 
and
Black's pieces are well placed to fight off White's attack on the dark squares.
12... Nxf3+ 13. Qxf3 e5 14. Be3 +- (or 14. Bd2)
An essential zwichenzug. White gets nothing out
of 14. axb3 Nd5 15. Nc4 Qc6
/=
14... Qb5
or 14... Qd8 15. axb3 Nf5 16. Qd2! with the idea of Ra5 or Qa5 and tremendous pressure on the White queenside which should win at least a pawn for White.
To prevent Ra5!
18. Re4!?
White misses the killer move at this juncture: 18. Qxf6+!! Kxf6 19. Be5+ Kg5 20. Bg7!!+- e5 (20... Rg8 21. f4+ Kg4 22. Ne5+ Kh5 23. Bf3#) 21. Rxe5+
18... Rd8?
But Black returns the favor. Essential, though lost, was 18... g5[] 19. Re5!-> 18... Rg8? 19. Qxf6+ Kxf6 20. Be5+ Kg5 21. Nd6!->
Position after 18...Rd8?
19. Qxf6+! Kxf6 20. Be5+ Kg5 21. Bg7!
White will force mate, as there is no defense to h4+ followed by Bh3 or Bf3# A Brilliant performance by Petrosian that demonstrates the power of the KIA on the dark squares.
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